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The circular economy is anticipated to bring a disruptive transformation in manufacturing technologies. Robust and industrial scalable microbial strains that can simultaneously assimilate and valorize multiple carbon substrates are highly desirable, as waste bioresources contain substantial amounts of renewable and fermentable carbon, which is diverse. Lignocellulosic biomass (LCB) is identified as an inexhaustible and alternative resource to reduce global dependence on oil. Glucose, xylose, and arabinose are the major monomeric sugars in LCB. However, primary research has focused on the use of glucose. On the other hand, the valorization of pentose sugars, xylose, and arabinose, has been mainly overlooked, despite possible assimilation by vast microbial communities. The present review highlights the research efforts that have explicitly proven the suitability of arabinose as the starting feedstock for producing various chemical building blocks via biological routes. It begins by analyzing the availability of various arabinose-rich biorenewable sources that can serve as potential feedstocks for biorefineries. The subsequent section outlines the current understanding of arabinose metabolism, biochemical routes prevalent in prokaryotic and eukaryotic systems, and possible products that can be derived from this sugar. Further, currently, exemplar products from arabinose, including arabitol, 2,3-butanediol, 1,2,3-butanetriol, ethanol, lactic acid, and xylitol are discussed, which have been produced by native and non-native microbial strains using metabolic engineering and genome editing tools. The final section deals with the challenges and obstacles associated with arabinose-based production, followed by concluding remarks and prospects. [ABSTRACT FROM AUTHOR]

Research background. An innovative integrated bioprocess system for bioethanol production from raw sugar beet cossettes (SBC) and arabitol from remaining exhausted sugar beet cossettes (ESBC) was studied. This integrated three-stage bioprocess system is an example of the biorefinery concept to maximise the use of raw SBC for the production of high value-added products such as sugar alcohols and bioethanol. Experimental approach. The first stage of the integrated bioprocess system was simultaneous sugar extraction from SBC and its alcoholic fermentation to produce bioethanol in an integrated bioreactor system (vertical column bioreactor and stirred tank bioreactor) containing a high-density suspension of yeast Saccharomyces cerevisiae (30 g/L). The second stage was the pretreatment of ESBC with dilute sulfuric acid to release fermentable sugars. The resulting liquid hydrolysate of ESBC was used in the third stage as a nutrient medium for arabitol production by non-Saccharomyces yeasts (Spathaspora passalidarum CBS 10155 and Spathaspora arborariae CBS 11463). Results and conclusions. The obtained results show that the efficiency of bioethanol production increased with increasing temperature and prolonged residence time in the integrated bioreactor system. The maximum bioethanol production efficiency (87.22 %) was observed at a time of 60 min and a temperature of 36 °C. Further increase in residence time (above 60 min) did not result in the significant increase of bioethanol production efficiency. Weak acid hydrolysis was used for ESBC pretreatment and the highest sugar yield was reached at 200 °C and residence time of 1 min. The inhibitors of the weak acid pretreatment were produced below bioprocess inhibition threshold. The use of the obtained liqiud phase of ESBC hydrolysate for the production of arabitol in the stirred tank bioreactor under constant aeration clearly showed that S. passalidarum CBS 10155 with 8.48 g/L of arabitol (YP/S=0.603 g/g and bioprocess productivity of 0.176 g/(L.h)) is a better arabitol producer than Spathaspora arborariae CBS 10155. Novelty and scientific contribution. An innovative integrated bioprocess system for the production of bioethanol and arabitol was developed based on the biorefinery concept. This three-stage bioprocess system shows great potential for maximum use of SBC as a feedstock for bioethanol and arabitol production and it could be an example of a sustainable ‘zero waste’ production system.

Ribitol (C5H12O5) is an acyclic sugar alcohol that was recently identified in O-mannose glycan on mammalian α-dystroglycan. The conformation and dynamics of acyclic sugar alcohols such as ribitol are dependent on the stereochemistry of the hydroxyl groups; however, the dynamics are not fully understood. To gain insights into the conformation and dynamics of sugar alcohols, we carried out comparative analyses of ribitol, d-arabitol and xylitol by a crystal structure database search, solution NMR analysis and molecular dynamics (MD) simulations. The crystal structures of the sugar alcohols showed a limited number of conformations, suggesting that only certain stable conformations are prevalent among all possible conformations. The three-bond scholar coupling constants and exchange rates of hydroxyl protons were measured to obtain information on the backbone torsion angle and possible hydrogen bonding of each hydroxyl group. The 100 ns MD simulations indicate that the ribitol backbone has frequent conformational transitions with torsion angles between 180° and ±60°, while d-arabitol and xylitol showed fewer conformational transitions. Taking our experimental and computational data together, it can be concluded that ribitol is more flexible than d-arabitol or xylitol, and the flexibility is at least in part defined by the configuration of the OH groups, which may form intramolecular hydrogen bonds. [ABSTRACT FROM AUTHOR]

Research background. An innovative integrated bioprocess system for bioethanol production from raw sugar beet cossettes (SBC) and arabitol from remaining exhausted sugar beet cossettes (ESBC) was studied. This integrated three-stage bioprocess system is an example of the biorefinery concept to maximise the use of raw SBC for the production of high value-added products such as sugar alcohols and bioethanol. Experimental approach. The first stage of the integrated bioprocess system was simultaneous sugar extraction from SBC and its alcoholic fermentation to produce bioethanol in an integrated bioreactor system (vertical column bioreactor and stirred tank bioreactor) containing a high-density suspension of yeast Saccharomyces cerevisiae (30 g/L). The second stage was the pretreatment of ESBC with dilute sulfuric acid to release fermentable sugars. The resulting liquid hydrolysate of ESBC was used in the third stage as a nutrient medium for arabitol production by non-Saccharomyces yeasts (Spathaspora passalidarum CBS 10155 and Spathaspora arborariae CBS 11463). Results and conclusions. The obtained results show that the efficiency of bioethanol production increased with increasing temperature and prolonged residence time in the integrated bioreactor system. The maximum bioethanol production efficiency (87.22 %) was observed at a time of 60 min and a temperature of 36 °C. Further increase in residence time (above 60 min) did not result in the significant increase of bioethanol production efficiency. Weak acid hydrolysis was used for ESBC pretreatment and the highest sugar yield was reached at 200 °C and residence time of 1 min. The inhibitors of the weak acid pretreatment were produced below bioprocess inhibition threshold. The use of the obtained liqiud phase of ESBC hydrolysate for the production of arabitol in the stirred tank bioreactor under constant aeration clearly showed that S. passalidarum CBS 10155 with 8.48 g/L of arabitol (YP/S=0.603 g/g and bioprocess productivity of 0.176 g/(L·h)) is a better arabitol producer than Spathaspora arborariae CBS 10155. Novelty and scientific contribution. An innovative integrated bioprocess system for the production of bioethanol and arabitol was developed based on the biorefinery concept. This three-stage bioprocess system shows great potential for maximum use of SBC as a feedstock for bioethanol and arabitol production and it could be an example of a sustainable 'zero waste' production system. [ABSTRACT FROM AUTHOR]

Polyalcohols such as arabitol are among the main targets of biorefineries aiming to upcycle wastes and cheap substrates. In previous works Wickerhamomyces anomalus WC 1501 emerged as an excellent arabitol producer utilizing glycerol. Arabitol production by this strain is not growth associated, therefore, in this study, pre-grown cells were entrapped in calcium alginate beads (AB) and utilized for glycerol transformation to arabitol. Flasks experiments aimed to assess the medium composition (i.e., the concentration of inorganic and organic nitrogen sources and phosphates) and to establish the appropriate carrier-to-medium proportion. In flasks, under the best conditions of ammonium limitation and the carrier:medium ratio of 1:3 (w/v), 82.7 g/L glycerol were consumed in 168 h, yielding 31.2 g/L arabitol, with a conversion of 38% and volumetric productivity of 186 mg/mL/h. The process with immobilized cells was transferred to laboratory scale bioreactors with different configurations: stirred tank (STR), packed bed (PBR), fluidized bed (FBR), and airlift (ALR) bioreactors. The STR experienced oxygen limitation due to the need to maintain low stirring to preserve AB integrity and performed worse than flasks. Limitations in diffusion and mass transfer of oxygen and/or nutrients characterized also the PBR and the FBR and were partially relieved only in ALR, where 89.4 g/L glycerol were consumed in 168 h, yielding 38.1 g/L arabitol, with a conversion of 42% and volumetric productivity of 227 mg/mL/h. When the ALR was supplied with successive pulses of concentrated glycerol to replenish the glycerol as it was being consumed, 117 g/L arabitol were generated in 500 h, consuming a total of 285 g/L glycerol, with a 41% and 234 mg/L/h. The study strongly supports the potential of W. anomalus WC 1501 for efficient glycerol-to-arabitol conversion using immobilized cells. While the yeast shows promise by remaining viable and active for extended periods, further optimization is required, especially regarding mixing and oxygenation. Improving the stability of the immobilization process is also crucial for reusing pre-grown cells in multiple cycles, reducing dead times, biomass production costs, and enhancing the economic feasibility of the process.

Abstract Arabitol is gaining attention in the food industry as an alternative sweetener owing to its low-caloric and non-cariogenic characteristics. The yeast strain kiy1 was newly isolated from unpasteurized honey for arabitol production. Based on internal transcribed spacer sequence analysis, the isolated strain was identified as Zygosaccharomyces siamensis. In this study, the effects of different substrates and sugar concentrations on arabitol production were investigated. When three types of carbon sources (glycerol, fructose, and glucose) were used, glucose was the most suitable substrate for arabitol production (68.7 g/L). Maximum arabitol production (101.4 g/L) was observed at a glucose concentration of 30%, and the highest arabitol production yield was 0.34 g/g of initial glucose. In the time-course production of sugar alcohols by strain kiy1, glucose was completely consumed for 8 days. The concentration of arabitol exceeded that of glycerol after 3 days, and the final arabitol concentration reached 83.6 g/L after 10 days. The maximum production rate was 16.7 g/L/day. The yeast produced glycerol as an intracellular sugar alcohol in the early stage of culture and switched its metabolism to arabitol production after the middle stage. Z. siamensis kiy1 possessed an NADP+-dependent arabitol dehydrogenase, which indicated that it probably produces arabitol via ribulose from glucose. These results suggest that the novel yeast strain, Z. siamensis kiy1, is promising for arabitol production. The proposed arabitol production approach can contribute toward its production at the industrial scale. Graphical Abstract

Arabitol is gaining attention in the food industry as an alternative sweetener owing to its low-caloric and non-cariogenic characteristics. The yeast strain kiy1 was newly isolated from unpasteurized honey for arabitol production. Based on internal transcribed spacer sequence analysis, the isolated strain was identified as Zygosaccharomyces siamensis. In this study, the effects of different substrates and sugar concentrations on arabitol production were investigated. When three types of carbon sources (glycerol, fructose, and glucose) were used, glucose was the most suitable substrate for arabitol production (68.7 g/L). Maximum arabitol production (101.4 g/L) was observed at a glucose concentration of 30%, and the highest arabitol production yield was 0.34 g/g of initial glucose. In the time-course production of sugar alcohols by strain kiy1, glucose was completely consumed for 8 days. The concentration of arabitol exceeded that of glycerol after 3 days, and the final arabitol concentration reached 83.6 g/L after 10 days. The maximum production rate was 16.7 g/L/day. The yeast produced glycerol as an intracellular sugar alcohol in the early stage of culture and switched its metabolism to arabitol production after the middle stage. Z. siamensis kiy1 possessed an NADP+-dependent arabitol dehydrogenase, which indicated that it probably produces arabitol via ribulose from glucose. These results suggest that the novel yeast strain, Z. siamensis kiy1, is promising for arabitol production. The proposed arabitol production approach can contribute toward its production at the industrial scale. Key points: Z. siamensis kiy1 was isolated as an arabitol producer from unpasteurized honey. Z. siamensis kiy1 produces arabitol under the high glucose conditions. Z. siamensis kiy1 may produce arabitol by NADP-dependent arabitol dehydrogenase. [ABSTRACT FROM AUTHOR]

Ribitol (C5H12O5) is an acyclic sugar alcohol that was recently identified in O-mannose glycan on mammalian α-dystroglycan. The conformation and dynamics of acyclic sugar alcohols such as ribitol are dependent on the stereochemistry of the hydroxyl groups; however, the dynamics are not fully understood. To gain insights into the conformation and dynamics of sugar alcohols, we carried out comparative analyses of ribitol, d-arabitol and xylitol by a crystal structure database search, solution NMR analysis and molecular dynamics (MD) simulations. The crystal structures of the sugar alcohols showed a limited number of conformations, suggesting that only certain stable conformations are prevalent among all possible conformations. The three-bond scholar coupling constants and exchange rates of hydroxyl protons were measured to obtain information on the backbone torsion angle and possible hydrogen bonding of each hydroxyl group. The 100 ns MD simulations indicate that the ribitol backbone has frequent conformational transitions with torsion angles between 180∘ and ±60∘, while d-arabitol and xylitol showed fewer conformational transitions. Taking our experimental and computational data together, it can be concluded that ribitol is more flexible than d-arabitol or xylitol, and the flexibility is at least in part defined by the configuration of the OH groups, which may form intramolecular hydrogen bonds.

Abstract Background d-Arabitol, a five-carbon sugar alcohol, represents a main target of microbial biorefineries aiming to valorize cheap substrates. The yeast Wickerhamomyces anomalus WC 1501 is known to produce arabitol in a glycerol-based nitrogen-limited medium and preliminary fed-batch processes with this yeast were reported to yield 18.0 g/L arabitol. Results Fed-batch fermentations with W. anomalus WC 1501 were optimized using central composite design (CCD). Dissolved oxygen had not a significant effect, while optimum values were found for glycerol concentration (114.5 g/L), pH (5.9), and temperature (32.5 °C), yielding 29 g/L d-arabitol in 160 h, a conversion yield of 0.25 g of arabitol per g of consumed glycerol, and a volumetric productivity of 0.18 g/L/h. CCD optimal conditions were the basis for further improvement, consisting in increasing the cellular density (3✕), applying a constant feeding of glycerol, and increasing temperature during production. The best performing fed-batch fermentations achieved 265 g/L d-arabitol after 325 h, a conversion yield of 0.74 g/g, and a volumetric productivity of 0.82 g/L/h. Conclusion W. anomalus WC 1501 confirmed as an excellent producer of d-arabitol, exhibiting a remarkable capability of transforming pure glycerol. The study reports among the highest values ever reported for microbial transformation of glycerol into d-arabitol, in terms of arabitol titer, conversion yield, and productivity. Graphical Abstract

Hemp hurds are the main byproduct from hemp fibers supply chain and they could represent valuable feedstock of lignocellulosic biomass for biorefineries. The industrial hemp variety "Carmagnola", is characterized by low amounts of ash and high amount of carbohydrates. Alpha-cellulose (44% w/w), hemicellulose (25%), and lignin (23%) were fractionated using an organosolv pretreatment. The enzymatic hydrolysis of the cellulose fraction yielded up to 60% of glucose, that can easily find application as substrate for industrial fermentations. On the other hand, the black liquor originating from hemicellulose contains mainly xylose and minor amounts of other sugars. In the perspective of finding an application of black liquor, 50 yeasts belonging to 24 ascomycetous species were screened both in aerobiosis and anaerobiosis for the production of ethanol and the sugar alcohols xylitol and arabitol from xylose. Pichia fermentans WC 1507, Wickerhamomyces anomalus WC 1501, and Kluyveromyces bacillosporus WC 1404 were found to consume xylose, yielding xylitol in aerobic conditions. In particular, aerobic flask cultures of P. fermentans WC 1507 containing 120 g/L xylose showed the highest xylitol production values, yielding 63.5 g/L xylitol with a YP/S of 71.5%. Black liquor, exploited as a carbon source, has been successfully utilized by the three selected yeast strains at a concentration of 20 g/L in the culture medium, resulting in comparable or higher yields of biomass and xylitol compared to the medium containing pure xylose. A higher concentration of black liquor in the culture medium (to reach 120 g/l of xylose) has determined an inhibition of the growth of yeasts indicating the need for treatments for the removal of inhibitors. These preliminary results can be considered promising for the microbial valorization of lignocellulosic hemp feedstock toward the production of xylitol. [ABSTRACT FROM AUTHOR]

In this study, a draft genome sequence of Zygosaccharomyces siamensis kiy1 isolated from unpasteurized honey in Japan was analyzed. This strain was reported to be a promising arabitol-producing strain, and this report contributes to a better understanding of arabitol production in yeasts.

Background: d-Arabitol, a five-carbon sugar alcohol, represents a main target of microbial biorefineries aiming to valorize cheap substrates. The yeast Wickerhamomyces anomalus WC 1501 is known to produce arabitol in a glycerol-based nitrogen-limited medium and preliminary fed-batch processes with this yeast were reported to yield 18.0 g/L arabitol. Results: Fed-batch fermentations with W. anomalus WC 1501 were optimized using central composite design (CCD). Dissolved oxygen had not a significant effect, while optimum values were found for glycerol concentration (114.5 g/L), pH (5.9), and temperature (32.5 °C), yielding 29 g/L d-arabitol in 160 h, a conversion yield of 0.25 g of arabitol per g of consumed glycerol, and a volumetric productivity of 0.18 g/L/h. CCD optimal conditions were the basis for further improvement, consisting in increasing the cellular density (3✕), applying a constant feeding of glycerol, and increasing temperature during production. The best performing fed-batch fermentations achieved 265 g/L d-arabitol after 325 h, a conversion yield of 0.74 g/g, and a volumetric productivity of 0.82 g/L/h. Conclusion: W. anomalus WC 1501 confirmed as an excellent producer of d-arabitol, exhibiting a remarkable capability of transforming pure glycerol. The study reports among the highest values ever reported for microbial transformation of glycerol into d-arabitol, in terms of arabitol titer, conversion yield, and productivity. [ABSTRACT FROM AUTHOR]

Even after 7 years of the nuclear accident that occurred in 2011 at the Fukushima Dai-ichi nuclear power plant (F1NPP), high levels of 137Cs have been detected in ambient aerosols from some polluted areas of Fukushima. Higher levels of radionuclides were often observed in the atmosphere during and after rain events. We presume that biological processes such as fungal activity associated with higher relative humidity may be involved with a possible emission of radioactivity to the atmosphere, which was originally emitted from the F1NPP accident and was deposited over the ground, forest, soil, etc. Here, we report, for the first time, relationships of 137Cs and organic tracers of fungal spores (i.e., arabitol, mannitol and trehalose) in the aerosol samples collected from Fukushima, Japan. Although we found twice-higher concentrations of 137Cs at nighttime than at daytime, fungal spore tracers did not show a consistent trend to 137Cs, that is, organic tracers at nighttime were similar with those at daytime or were even higher in daytime. This study has not clearly demonstrated that fungal spores are the important source of high levels of 137Cs at nighttime. The current unclear relationship is probably associated with the sampling strategy (four consecutive days with a sampling on/off program for day/nighttime samples) taken in this campaign, which may have caused a complicated meteorological situation. [ABSTRACT FROM AUTHOR]

Xylitol is a widely marketed sweetener with good functionality and health-promoting properties. It can be synthetized by many yeast species in a one-step reduction of xylose. Arabinose is a common contaminant found in xylose and there is ongoing interest in finding biocatalysts that selectively produce xyltiol. From a screen of 99 yeasts, Barnettozyma populi Y-12728 was found to selectively produce xylitol from both mixed sugars and corn stover hemicellulosic hydrolysate. Here, fermentation conditions for xylitol production from xylose by B. populi were optimized. The medium for xylitol production was optimized through response surface methodology. The yeast produced 31.2 ± 0.4 g xylitol from xylose (50 g L−1) in 62 h using the optimized medium. The optimal pH for xylitol production was 6.0. Glucose (10 g L−1), acetic acid (6.0 g L−1), HMF (4 mM) and ethanol (2.0 g L−1) inhibited the xylitol production. The glucose inhibition was entirely mitigated by using a 2-stage aeration strategy, indicating that the yeast was inhibited by ethanol produced from glucose under low aeration. This culture strategy will greatly benefit xylitol production from hemicellulosic hydrolysates, which often contain glucose. This is the first report on optimization of xylitol production by a Barnettozyma species. [ABSTRACT FROM AUTHOR]

The main goal of this study was to screen different lignocellulosic materials for their ability to support the cell growth of the yeast Komagataella pastoris and the production of xylitol. Several lignocellulosic materials, namely banana peels, brewer's spent grains (BSGs), corncobs, grape pomace, grape stalks, and sawdust, were subjected to dilute acid hydrolysis to obtain sugar rich solutions that were tested as feedstocks for the cultivation of K. pastoris. Although the culture was able to grow in all the tested hydrolysates, a higher biomass concentration was obtained for banana peels (15.18 ± 0.33 g/L) and grape stalks (14.58 ± 0.19 g/L), while the highest xylitol production (1.51 ± 0.07 g/L) was reached for the BSG hydrolysate with a xylitol yield of 0.66 ± 0.39 g/g. Cell growth and xylitol production from BSG were improved by detoxifying the hydrolysate using activated charcoal, resulting in a fourfold increase of the biomass production, while xylitol production was improved to 3.97 ± 0.10 g/L. Moreover, concomitant with arabinose consumption, arabitol synthesis was noticed, reaching a maximum concentration of 0.82 ± 0.05 g/L with a yield on arabinose of 0.60 ± 0.11 g/g. These results demonstrate the feasibility of using lignocellulosic waste, especially BSG, as feedstock for the cultivation of K. pastoris and the coproduction of xylitol and arabitol. Additionally, it demonstrates the use of K. pastoris as a suitable microorganism to integrate a zero-waste biorefinery, transforming lignocellulosic waste into two high-value specialty chemicals with high market demand. [ABSTRACT FROM AUTHOR]

To set-up afforestation and reforestation projects in arid regions southern Tunisia, several indigenous and exotic forest species were used among them are Acacia spp. However, the success of these projects remains highly sceptical because of the intensified aridity during the last decade. To overcome this issue, the selection of genotypes resistant to severe drought is crucial as first step. For this reason, the aim of the present study is to compare tolerance capacity to severe drought between two Acacia species (A. cyclops and A. salicina) and evaluate efficacy of their biochemical responses at leaf and root levels. Combined physiological and biochemical approaches were adopted. Two-years-old plants of two Acacia species (A. cyclops and A. salicina), frequently used in forestation projects in arid regions southern Tunisia, were subjected to severe water stress by withholding watering during 60 days. At regular intervals, water relations and net photosynthetic rate (Pn) were measured. In addition, the biochemical response was characterized by quantifying one sugar alcohol (arabitol) and three cyclitols (myo-inositol, pinitol and quercitol) in leaves and roots. Our results revealed that A. cyclops was more tolerant to severe drought than A. salicina. The turgor of its leaf tissues and its Pn were less affected. The superiority of A. cyclops to tolerate severe water stress might be attributed to greater efficiency of its biochemical defense mechanisms compared to A. salicina. Comparison of biochemical profiles between species exhibited some differences depending on the organs and the species. For development and survival under severe drought conditions, A. cyclops accomplished efficient osmoregualation and osmoprotection mechanisms by massive accumulation of specific polyols distinctly in leaves and roots. Indeed, compared to A. salicina, A. cyclops accumulated higher amount of arabitol, myo-inositol and quercitol in roots, but pinitol in leaves. So, contents of these polyols might be used as promising criteria for the selection of drought-tolerant Acacia species.

To set-up afforestation and reforestation projects in arid regions southern Tunisia, several indigenous and exotic forest species were used among them are Acacia spp. However, the success of these projects remains highly sceptical because of the intensified aridity during the last decade. To overcome this issue, the selection of genotypes resistant to severe drought is crucial as first step. For this reason, the aim of the present study is to compare tolerance capacity to severe drought between two Acacia species (A. cyclops and A. salicina) and evaluate efficacy of their biochemical responses at leaf and root levels. Combined physiological and biochemical approaches were adopted. Two-years-old plants of two Acacia species (A. cyclops and A. salicina), frequently used in forestation projects in arid regions southern Tunisia, were subjected to severe water stress by withholding watering during 60 days. At regular intervals, water relations and net photosynthetic rate (Pn) were measured. In addition, the biochemical response was characterized by quantifying one sugar alcohol (arabitol) and three cyclitols (myo-inositol, pinitol and quercitol) in leaves and roots. Our results revealed that A. cyclops was more tolerant to severe drought than A. salicina. The turgor of its leaf tissues and its Pn were less affected. The superiority of A. cyclops to tolerate severe water stress might be attributed to greater efficiency of its biochemical defense mechanisms compared to A. salicina. Comparison of biochemical profiles between species exhibited some differences depending on the organs and the species. For development and survival under severe drought conditions, A. cyclops accomplished efficient osmoregualation and osmoprotection mechanisms by massive accumulation of specific polyols distinctly in leaves and roots. Indeed, compared to A. salicina, A. cyclops accumulated higher amount of arabitol, myo-inositol and quercitol in roots, but pinitol in leaves. So, contents of these polyols might be used as promising criteria for the selection of drought-tolerant Acacia species. [ABSTRACT FROM AUTHOR]

The hydrolysis–hydrogenation of arabinogalactan hemicellulose to valuable polyalcohols arabitol and galactitol, which are widely used in the food and pharmaceutical industries, is studied. The possibility of using a bifunctional catalyst containing disperse ruthenium supported on cesium salt of heteropolyacid Ru/Cs3HSiW12O40 for the process is demonstrated. A series of catalysts with different contents of the noble metal (0.3, 0.6 and 1 wt %) were prepared. Physicochemical techniques (low temperature nitrogen adsorption, IR spectroscopy, XRD, TEM) are used to characterize the prepared catalysts and the Cs3HSiW12O40 support. The effect the temperature and the substrate : catalyst ratio, and the content of ruthenium in the catalyst, have on the yields of the target products is studied. The highest yields of arabitol and galactitol were observed for a catalyst containing 0.6 wt % of Ru at a substrate : catalyst ratio of 1 : 1. Arabitol and galactitol can be produced with yields of 12 and 48%, respectively, at 200°C in the presence of 0.6%Ru/Cs3HSiW12O40 catalyst. [ABSTRACT FROM AUTHOR]

Polyalcohols such as arabitol are among the main targets of biorefineries aiming to upcycle wastes and cheap substrates. In previous works Wickerhamomyces anomalus WC 1501 emerged as an excellent arabitol producer utilizing glycerol. Arabitol production by this strain is not growth associated, therefore, in this study, pre-grown cells were entrapped in calcium alginate beads (AB) and utilized for glycerol transformation to arabitol. Flasks experiments aimed to assess the medium composition (i.e., the concentration of inorganic and organic nitrogen sources and phosphates) and to establish the appropriate carrier-to-medium proportion. In flasks, under the best conditions of ammonium limitation and the carrier:medium ratio of 1:3 (w/v), 82.7 g/L glycerol were consumed in 168 h, yielding 31.2 g/L arabitol, with a conversion of 38% and volumetric productivity of 186 mg/mL/h. The process with immobilized cells was transferred to laboratory scale bioreactors with different configurations: stirred tank (STR), packed bed (PBR), fluidized bed (FBR), and airlift (ALR) bioreactors. The STR experienced oxygen limitation due to the need to maintain low stirring to preserve AB integrity and performed worse than flasks. Limitations in diffusion and mass transfer of oxygen and/or nutrients characterized also the PBR and the FBR and were partially relieved only in ALR, where 89.4 g/L glycerol were consumed in 168 h, yielding 38.1 g/L arabitol, with a conversion of 42% and volumetric productivity of 227 mg/mL/h. When the ALR was supplied with successive pulses of concentrated glycerol to replenish the glycerol as it was being consumed, 117 g/L arabitol were generated in 500 h, consuming a total of 285 g/L glycerol, with a 41% and 234 mg/L/h. The study strongly supports the potential of W. anomalus WC 1501 for efficient glycerol-to-arabitol conversion using immobilized cells. While the yeast shows promise by remaining viable and active for extended periods, further optimization is required, especially regarding mixing and oxygenation. Improving the stability of the immobilization process is also crucial for reusing pre-grown cells in multiple cycles, reducing dead times, biomass production costs, and enhancing the economic feasibility of the process., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. The authors declared that they were an editorial board member of Frontiers, at the time of submission. This had no impact on the peer review process and the final decision., (Copyright © 2024 Ranieri, Candeliere, Sola, Leonardi, Rossi, Amaretti and Raimondi.)

Even after 7 years of the nuclear accident that occurred in 2011 at the Fukushima Dai-ichi nuclear power plant (F1NPP), high levels of 137Cs have been detected in ambient aerosols from some polluted areas of Fukushima. Higher levels of radionuclides were often observed in the atmosphere during and after rain events. We presume that biological processes such as fungal activity associated with higher relative humidity may be involved with a possible emission of radioactivity to the atmosphere, which was originally emitted from the F1NPP accident and was deposited over the ground, forest, soil, etc. Here, we report, for the first time, relationships of 137Cs and organic tracers of fungal spores (i.e., arabitol, mannitol and trehalose) in the aerosol samples collected from Fukushima, Japan. Although we found twice-higher concentrations of 137Cs at nighttime than at daytime, fungal spore tracers did not show a consistent trend to 137Cs, that is, organic tracers at nighttime were similar with those at daytime or were even higher in daytime. This study has not clearly demonstrated that fungal spores are the important source of high levels of 137Cs at nighttime. The current unclear relationship is probably associated with the sampling strategy (four consecutive days with a sampling on/off program for day/nighttime samples) taken in this campaign, which may have caused a complicated meteorological situation.

Background Human milk composition is altered by maternal obesity. The association between milk metabolites and infant outcomes has not been thoroughly investigated. Objectives This study aimed to quantify maternal adiposity-related differences in the human milk metabolome and to identify metabolites associated with infant adiposity during the first 6 mo postpartum using untargeted metabolomics. Method Maternal anthropometrics were assessed ≤14 weeks of gestation. Human milk samples were collected at 0.5 mo (n  = 159), 2 mo (n  = 131), and 6 mo (n  = 94) postpartum from normal weight (NW, BMI = 18.5–24.9 kg/m2) and obese (OB, BMI >30 kg/m2) mothers. GC-time-of-flight-MS was used to identify metabolic signatures that discriminate NW and OB women. Partial least squared (PLS)-discriminant analysis, and PLS-regression models were assessed to examine relations between metabolites and maternal BMI and fat mass. Metabolites altered by maternal obesity were used in linear mixed effect models to predict infant adiposity. Results Multivariate modeling identified 23, 17, and 10 metabolites that described maternal adiposity indices at 0.5 mo, 2 mo, and 6 mo postpartum, respectively. Monosaccharides and sugar alcohols were the most representative annotated metabolite classes that were increased in milk from OB women and included: mannose, ribose, lyxose, lyxitol (0.5 mo); mannose, ribitol, glycerol, isothreonic acid, lyxitol (2 mo); lyxitol and isothreonic acid (6 mo). Other discriminant metabolites included: 1-monostearin, xylonolactone, shikimic acid, pseudo uridine, and dodecanol (0.5 mo); N -acetyl-D-hexosamine and fumaric acid (2 mo); uric acid and tyrosine (6 mo). Mannose, lyxitol, and shikimic acid predicted higher infant adiposity over the first 6 mo of life. Conclusions This study reports on 1 of the largest cohorts to date examining the metabolic profiles in human milk comparing NW and OB women. Maternal adiposity was associated with increased amounts of milk nonglucose monosaccharides. Human milk metabolomics may be useful in predicting infant adiposity. These trials were registered at www.clinicaltrials.gov as NCT01131117 and NCT02125149. [ABSTRACT FROM AUTHOR]

The process design for synthesis of arabitol by hydrogenation of arabinose on a supported ruthenium catalyst is described. Aspen HYSYS software was used to design an arabitol production plant for subsequent generation of hydrogen through aqueous phase reforming (APR). The process design included hydrogen recycling requiring a flash drum and recompression. The total costs of arabitol were estimated to be substantially dependent on the feedstock costs and are closely related to arabinose feed cost. Feasible production of hydrogen using APR requires efficient extraction of hemicellulose from lignocellulosic biomass and subsequent hydrolysis. [ABSTRACT FROM AUTHOR]

BACKGROUND: Lipids produced from oleaginous yeasts are a promising alternative to terrestrial oils. Despite promising cellular yields of lipid however, an industrial process remains elusive. One key processing bottleneck is the need to provide nutrient‐rich conditions for cellular growth and then extended nutrient‐depleted conditions for lipid accumulation. Surprisingly, investigations detailing process development, particularly with a focus on kinetics, are rare in this field. RESULTS: In this investigation we report on the unique oleaginous yeast Metschnikowia pulcherrima, where lipid accumulation ≥ 29.8% (w/w) was achieved without apparent nutrient limitation. The process was developed in stirred tank reactors through determining the influence of temperature, pH and nutrition on lipid production. A temperature of up to 25 °C and initial pH 5 could be applied to enhance initial reaction kinetics. Through the increased supply of yeast extract of up to 5% (w/w) of glucose, a maximum lipid production rate of 0.60 g L−1 h−1 (4 h‐average), productivity of 0.29 g L−1 h−1, and yield of 0.17 g g−1 glucose were achieved – the highest yet recorded with this yeast. Suitable to combat the excessive secretion of polyols of up to 0.11 g g−1 glucose was an excess nutrient supply as well as a low cultivation temperature of 15 °C and moderate pH 5. CONCLUSIONS: This study demonstrates that the lack of a starvation stage, coupled with effective process development is required for oleaginous yeasts to achieve the yields and productivities required for commercial lipid production. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

• Volumetric and acoustic study of biologically important compound in electrolytic solutions. • Chaotropic and kosmotropic behavior of ions in aqueous solution of polyhydroxy compound at different temperatures. • Sweetness response has been calculated using Apparent specific volume. • Structure-making behavior of arabitol in aqueous electrolytic solutions. Hydrated ions have essential applications in biochemical processes. The objective of the present work is to study the behaviour of kosmotropic and chaotropic ions in aqueous solutions of polyhydroxy compounds in terms of sweetness response, volumetric and acoustic parameters such as apparent molar volume (∅ v), apparent specific volume (ASV), compressibility (∅ k 0) etc. at different temperatures 20 °C – 45 °C and 101 kPa. The positive ∅ v values of arabitol showed more kosmotropic nature for Na+ ion developing more stabilize structure of arabitol with water through strong hydrogen bonding, while the presence of K+ and Cl- form weak hydrogen bonding with water termed as chaotropic ions. The ASV values showed that arabitol remained sweet in the presence of electrolytes. The negative results of ∅ k 0 for arabitol in aqueous electrolytic solutions give valuable information about interactions occurring among solute, electrolytic ions, and water molecules. The structure-making/breaking behaviour has been observed by Hepler's constant (∂ 2 ∅ v o / ∂ T 2) p. [ABSTRACT FROM AUTHOR]

Polyalcohol arabitol can be used in the food and pharmaceutical industries as a natural sweetener, a dental caries reducer, and texturing agent. Environmental samples were screened to isolate effective yeast producers of arabitol. The most promising isolate 27RL-4, obtained from raspberry leaves, was identified genetically and biochemically as Candida parapsilosis. It secreted 10.42– 10.72 g l-1 of product from 20 g l-1 of L-arabinose with a yield of 0.51 - 0.53 g g-1 at 28°C and a rotational speed of 150 rpm. Batch cultures showed that optimal pH value for arabitol production was 5.5. High yields and productivities of arabitol were obtained during incubation of the yeast at 200 rpm, or at 32°C, but the concentrations of the polyol did not exceed 10 g l-1. In modified medium, with reduced amounts of nitrogen compounds and pH 5.5-6.5, lower yeast biomass produced a similar concentration of arabitol, suggesting higher efficiency of yeast cells. This strain also produced arabitol from glucose, with much lower yields. The search for new strains able to successfully produce arabitol is important for allowing the utilization of sugars abundant in plant biomass.

The main goal of this study was to screen different lignocellulosic materials for their ability to support the cell growth of the yeast Komagataella pastoris and the production of xylitol. Several lignocellulosic materials, namely banana peels, brewer’s spent grains (BSGs), corncobs, grape pomace, grape stalks, and sawdust, were subjected to dilute acid hydrolysis to obtain sugar rich solutions that were tested as feedstocks for the cultivation of K. pastoris. Although the culture was able to grow in all the tested hydrolysates, a higher biomass concentration was obtained for banana peels (15.18 ± 0.33 g/L) and grape stalks (14.58 ± 0.19 g/L), while the highest xylitol production (1.51 ± 0.07 g/L) was reached for the BSG hydrolysate with a xylitol yield of 0.66 ± 0.39 g/g. Cell growth and xylitol production from BSG were improved by detoxifying the hydrolysate using activated charcoal, resulting in a fourfold increase of the biomass production, while xylitol production was improved to 3.97 ± 0.10 g/L. Moreover, concomitant with arabinose consumption, arabitol synthesis was noticed, reaching a maximum concentration of 0.82 ± 0.05 g/L with a yield on arabinose of 0.60 ± 0.11 g/g. These results demonstrate the feasibility of using lignocellulosic waste, especially BSG, as feedstock for the cultivation of K. pastoris and the coproduction of xylitol and arabitol. Additionally, it demonstrates the use of K. pastoris as a suitable microorganism to integrate a zero-waste biorefinery, transforming lignocellulosic waste into two high-value specialty chemicals with high market demand.

Aims: To assess the ability of various newly isolated or belonging in official collections yeast strains to convert biodiesel‐derived glycerol (Gly) into added‐value compounds. Methods and Results: Ten newly isolated yeast strains belonging to Debaryomyces sp., Naganishia uzbekistanensis, Rhodotorula sp. and Yarrowia lipolytica, isolated from fishes, metabolized Gly under nitrogen limitation. The aim of the study was to identify potential newly isolated microbial candidates that could produce single‐cell oil (SCO), endopolysaccharides and polyols when these micro‐organisms were grown on biodiesel‐derived Gly. As controls producing SCO and endopolysaccharides were the strains Rhodotorula glutinis NRRL YB‐252 and Cryptococcus curvatus NRRL Y‐1511. At initial Gly (Gly0) ≈40 g l−1, most strains presented remarkable dry cell weight (DCW) production, whereas Y. lipolytica and Debaryomyces sp. produced non‐negligible quantities of mannitol and arabitol (Ara). Five strains were further cultivated at increasing Gly0 concentrations. Rhodotorula glutinis NRRL YB‐252 produced 7·2 g l−1 of lipid (lipid in DCW value ≈38% w/w), whereas Debaryomyces sp. FMCC Y69 in batch‐bioreactor experiment with Gly0 ≈80 g l−1, produced 30–33 g l−1 of DCW and ~30 g l−1 of Ara. At shake‐flasks with Gly0 ≈125 g l−1, Ara of ~48 g l−1 (conversion yield of polyol on Gly consumed ≈0·62 g g−1) was achieved. Cellular lipids of all yeasts contained in variable concentrations oleic, palmitic, stearic and linoleic acids. Conclusions: Newly isolated, food‐derived and non‐previously studied yeast isolates converted biodiesel‐derived Gly into several added‐value metabolites. Significance and Impact of the Study: Alternative ways of crude Gly valorization through yeast fermentations were provided and added‐value compounds were synthesized. [ABSTRACT FROM AUTHOR]

The AraR transcription factor of Aspergillus niger encodes a Zn(II)2Cys6 transcription factor required for the induction of genes encoding arabinolytic enzymes. One of the target genes of AraR is abfA, encoding an arabinofuranosidase. The expression of abfA as well as other L-arabinose-induced genes in A. niger requires the presence of L-arabinose or its derivative L-arabitol as an inducer to activate AraR-dependant gene expression. In this study, mutants were isolated that express L-arabinose-induced genes independently of the presence of an inducer under derepressing conditions. To obtain these mutants, a reporter strain was constructed in a ΔcreA background containing the L-arabinose-responsive promoter (PabfA) fused to the acetamidase (amdS) gene. Spores of the ΔcreA PabfA-amdS reporter strain were UV-mutagenized and mutants were obtained by their ability to grow on acetamide without the presence of inducer. From a total of 164 mutants, 15 mutants were identified to contain transacting mutations resulting in high arabinofuranosidase activity in the medium after growth under non-inducing conditions. Sequencing of the araR gene of the 15 constitutive mutants revealed that 14 mutants carried a mutation in AraR. Some mutations were found more than once and in total nine different point mutations were identified in AraR. The AraRN806I point mutation was reintroduced into a parental strain and confirmed that this point mutation leads to inducer-independent expression of AraR target genes. The inducer independent of L-arabinose-induced genes in the AraRN806I mutant was found to be sensitive to carbon catabolite repression, indicating that the CreA-mediated carbon catabolite repression is dominant over the AraRN806I mutant allele. These mutations in AraR provide new opportunities to improve arabinase production in industrial fungal strains. [ABSTRACT FROM AUTHOR]

Abstract Despite the worldwide consumption of bovine milk, dairy products from small ruminants, such as goat's and sheep's milk, are gaining a large interest especially in the Mediterranean area. The aim of this work was to study the metabolite profiles of 30 sheep's and 28 goat's milk using an untargeted metabolomics approach by a gas chromatography coupled with mass spectrometry (GC-MS) analysis. Results showed several differences in the metabolite profiles: arabitol, citric acid, α˗ketoglutaric acid, glyceric acid, myo˗ inositol, and glycine were more abundant in sheep's milk, while goat's milk had higher levels of mannose˗6˗phosphate, isomaltulose, valine, pyroglutamic acid, leucine, and fucose. Associations between metabolite profile and milk compositional traits were also found. Predictive capabilities of statistical models indicated a good correlation between the metabolite profile and the protein content in sheep's milk, and with the fat content in goat's milk. This work leads to a better understanding of milk metabolites in small ruminants and their role in the evaluation of milk properties. Graphical abstract Unlabelled Image Highlights • Goat's and sheep's milk are gaining interest for nutritional and health effects. • Metabolomics has been applied to study dairy products. • Milk metabolites can reflect the physiological mechanism of milk production. • Sheep's milk was found richer in myo -inositol. • Metabolite profiles were associated to milk traits, such as fat, proteins and SCC. [ABSTRACT FROM AUTHOR]

Arabitol has several applications in food and pharmaceutical industries as a natural sweetener, dental caries inhibitor, and texturing agent. Newly isolated yeast strains from seawater, sugarcane plantation soil samples, and Zygosaccharomyces rouxii 2635 from MTCC were tested for arabitol production. The yield of arabitol was found to be higher in seawater isolate (24.6 g L−1) compared to two soil isolates (22.5 g L−1) and Z. rouxii (19.4 g L−1). Based on ITS 26S rDNA sequence analysis, the seawater isolate was identified as Pichia manchurica. In the present study, the effect of different substrates, trace elements, nitrogen sources, pH, and temperature on arabitol production was examined. Three different carbon sources viz. glucose, arabinose, and galactose were studied. Glucose was determined to be the best substrate for arabitol production (27.6 g L−1) followed by arabinose (13.7 g L−1) and galactose (7.7 g L−1). Maximum production of arabitol was observed at pH 6.0 (34.7 g L−1). In addition, arabitol production was high (35.7 g L−1) at temperature of 30 °C. Among the different concentrations of ammonium sulfate tested (3, 4.5, 6, 7.5, and 9 g L−1) concentration of 6 g L−1 resulted in higher arabitol Individual metal ions had no effect on arabitol production by this strain as compared to control. Results obtained in this study identify ways for improved arabitol production with natural isolates using microbial processes. [ABSTRACT FROM AUTHOR]

Abstract A newly isolated yeast strain, namely Zygosaccharomyces rouxii JM-C46, was reported to be promising for enhanced D -arabitol production from glucose. In this study, further efforts were made to optimize fermentation conditions for this strain through one-factor-at-a-time strategy considering seven important factors of shake flask fermentation. Subsequently, composition of fermentation medium was optimized using Box-Behnken design (BBD) of response surface methodology (RSM) including three major nitrogen providing ingredients, namely yeast extract, (NH 4) 2 SO 4 and peptone. Maximum D-arabitol concentration produced in one-factor-at-a-time experiments was found to be 72.69 g/L under the optimum conditions consisting of 200 g/L initial glucose, 100 ml medium, 5% (equivalent to 8.78 g/L) initial inoculum, temperature 30 °C, pH 5.0, fermentation time 96 h, and agitation rate 200 rpm. In the experiments of BBD, the predicted yield of D-arabitol varied between 67.73 g/L and 76.76 g/L, while the actual concentration of D-arabitol ranged from 68.02 g/L to 76.95 g/L. The optimum composition of medium F (final medium) contained d -glucose (200 g/L), yeast extract (10 g/L), (NH 4) 2 SO 4 (2 g/L) and peptone (7.5 g/L), which further increased D-arabitol production from 72.69 g/L to 76.32 g/L. Highlights • Effects of various fermentation factors were evaluated for D-arabitol production. • Fermentation medium was optimized for a new strain Zygosaccharomyces rouxii JM-C46. • Maximum D-arabitol was found to be 72.69 g/L under optimum fermentation conditions. • D-arabitol production further increased to 76.32 g/L using optimum medium composition. [ABSTRACT FROM AUTHOR]

• Arabitol, mannitol and trehalose are the most common fungal saccharides. • Modern white rot fungi are mainly dominated by trehalose. • In brown and soft rot fungi, arabitol predominates. • The distribution of sugars differs between the Paleocene/Eocene and Miocene lignites. • Soft rot fungi are probably precursors of increased amounts of saccharols in Paleocene/Eocene lignites. Fungi are a common component of terrestrial ecosystems, although their preservation as molecular fossils is relatively rare. Saccharides, such as arabitol, mannitol and trehalose, are important in biochemical processes, and are the dominant compounds in fungi, lichens and yeasts. Here we present gas chromatography–mass spectrometry (GC–MS) analysis of fungal saccharides in brown coal extracts and compare their distribution to extant white, brown, and soft-rot fungi. Distribution differs depending on the type of decay in modern and fossil wood-decomposing fungi. An arabitol/(arabitol + trehalose) ratio higher than 0.6 for extant and fossil fungi is diagnostic for soft and brown rot, while values below 0.4 are characteristic of white rot fungi. Values between 0.4 and 0.6 suggest a mixed origin of fungal saccharides. The observed differences may shed light on the type of fungal activity, in particular relatated to climatic conditions of the Cenozoic. We conclude that saccharides can be good indicators, sensitive to climate change, of wood degradation by fungi in thermally immature organic matter. As a case study, early Cenozoic lignites were formed on low latitudes in the tropics during or near the Paleocene/Eocene thermal maximum, as extant soft rot fungi can withstand extremes of temperature and humidity. The presence of these fungi is confirmed by the dominance of arabitol over trehalose in most of the Lower Cenozoic lignites and arabitol/(arabitol + trehalose) ratio values higher than 0.6. In contrast, Miocene detritic coals, which were formed in temperate to subtropical climates, contain saccharides derived from a mixture of different fungi with white rot predominance. [ABSTRACT FROM AUTHOR]

Lactic acid is the monomeric unit of polylactide (PLA), a bioplastic widely used in the packaging, automotive, food, and pharmaceutical industries. Previously, the yeast Komagataella phaffii was genetically modified for the production of lactate from glycerol. For this, the bovine L-lactate dehydrogenase- (LDH)-encoding gene was inserted and the gene encoding the pyruvate decarboxylase (PDC) was disrupted, resulting in the GLp strain. This showed a yield of 67% L-lactic acid and 20% arabitol as a by-product in batches with oxygen limitation. Following up on these results, the present work endeavored to perform a detailed study of the metabolism of this yeast, as well as perturbing arabitol synthesis in an attempt to increase lactic acid titers. The GLp strain was cultivated in a glycerol-limited chemostat at different dilution rates, confirming that the production of both lactic acid and arabitol is dependent on the specific growth rate (and consequently on the concentration of the limiting carbon source) as well as on the oxygen level. Moreover, disruption of the gene encoding arabitol dehydrogenase (ArDH) was carried out, resulting in an increase of 20% in lactic acid and a 50% reduction in arabitol. This study clarifies the underlying metabolic reasons for arabitol formation in K. phaffii and points to ways for improving production of lactic acid using K. phaffii as a biocatalyst.

Arabitol is used in the food industry as a low-calorie sweetener. It is produced by yeasts during the biotransformation process of L-arabinose. Genome shuffling was performed in Candida parapsilosis DSM 70125, an efficient producer of arabitol, to obtain fusants with improved arabitol production ability. Four mutants from the parental library were used for the first round of genome shuffling. The best fusants, GSI-1 and GSI-10A, were subjected to a second round of genome shuffling. Finally, two fusants, GSII-3 and GSII-16, produced concentrations of arabitol that were 50% higher than that of the wild-type strain during selection culture. Under the optimal conditions established for C. parapsilosis, the two fusants produced 11.83 and 11.75 g/L of arabitol and were approximately 15-16% more efficient than the wild-type strain. Flow cytometry analysis showed that the ploidy of the new strains did not change. [ABSTRACT FROM AUTHOR]

Lactic acid is the monomer unit of the bioplastic poly-lactic acid (PLA). One candidate organism for lactic acid production is Pichia pastoris, a yeast widely used for heterologous protein production. Nevertheless, this yeast has a poor fermentative capability that can be modulated by controlling oxygen levels. In a previous study, lactate dehydrogenase (LDH) activity was introduced into P. pastoris, enabling this yeast to produce lactic acid. The present study aimed to increase the flow of pyruvate towards the production of lactic acid in P. pastoris. To this end, a strain designated GLp was constructed by inserting the bovine lactic acid dehydrogenase gene (LDHb) concomitantly with the interruption of the gene encoding pyruvate decarboxylase (PDC). Aerobic fermentation, followed by micro-aerophilic culture two-phase fermentations, showed that the GLp strain achieved a lactic acid yield of 0.65 g/g. The distribution of fermentation products demonstrated that the acetate titer was reduced by 20% in the GLp strain with a concomitant increase in arabitol production: arabitol increased from 0.025 g/g to 0.174 g/g when compared to the GS115 strain. Taken together, the results show a significant potential for P. pastoris in producing lactic acid. Moreover, for the first time, physiological data regarding co-product formation have indicated the redox balance limitations of this yeast. [ABSTRACT FROM AUTHOR]

Arabitol is a low-calorie sugar alcohol with anti-cariogenic properties. Enzymatic hydrolysate of soybean flour is a new renewable biorefinery feedstock containing hexose, pentose, and organic nitrogen sources. Arabitol production by Debaryomyces hansenii using soybean flour hydrolysate was investigated. Effects of medium composition, operating conditions, and culture stage (growing or stationary phase) were studied. Production was also compared at different culture volumes to understand the effect of dissolved oxygen concentration (DO). Main factors examined for medium composition effects were the carbon to nitrogen concentration ratio (C/N), inorganic (ammonium) to organic nitrogen ratio (I/O-N), and sugar composition. Arabitol yield increased with increasing C/N ratio and a high I/O-N (0.8-1.0), suggesting higher yield at stationary phase of low pH (3.5-4.5). Catabolite repression was observed, with the following order of consumption: glucose > fructose > galactose > xylose > arabinose. Arabitol production also favored hexoses and, among hexoses, glucose. DO condition was of critical importance to arabitol production and cell metabolism. The yeast consumed pentoses (xylose and arabinose) only at more favorable DO conditions. Finally, arabitol was produced in fermentors using mixed hydrolysates of soy flour and hulls. The process gave an arabitol yield of 54%, volumetric productivity of 0.90 g/L-h, and specific productivity of 0.031 g/g-h. [ABSTRACT FROM AUTHOR]

Comparative composition of lipids and cytosol soluble carbohydrates at different ambient pH values was studied for two obligately alkaliphilic fungi ( Sodiomyces magadii and S. alkalinus) and for two alkalitolerant ones ( Acrostalagmus luteoalbus and Chordomyces antarcticus). The differences and common patterns were revealed in responses to pH stress for the fungi with different types of adaptation to ambient pH. While trehalose was one of the major cytosol carbohydrates in alkaliphilic fungi under optimal growth conditions (pH 10.2), pH decrease to 7.0 resulted in doubling its content. In alkalitolerant fungi trehalose was a minor component and its level did not change significantly at different pH. In alkalitolerant fungi, arabitol and mannitol were the major carbohydrate components, with their highest ratio observed under alkaline conditions and the lowest one, under neutral and acidic conditions. In alkaliphiles, significant levels of arabitol were revealed only under alkaline conditions, which indicated importance of trehalose and arabitol for alkaliphily. Decreased pH resulted in the doubling of the proportion of phosphatidic acids among the membrane lipids, which was accompanied by a decrease in the fractions of phosphatidylcholines and sterols. Alkalitolerant fungi also exhibited a decrease in sterol level at decreased pH, but against the background of increased proportion of one of phospholipids. Decreased unsaturation degree in the fatty acids of the major phospholipids was a common response to decreased ambient pH. [ABSTRACT FROM AUTHOR]

The sugar alcohol d-arabitol is one of the Department of Energy's top twelve bio-based building block chemicals. In this study, we found that the oleaginous yeast Rhodosporidium toruloides IFO0880 produces d-arabitol during growth on xylose in nitrogen-rich medium. Efficient xylose utilization was a prerequisite for extracellular d-arabitol production. During growth in complex media, R. toruloides produced 22 ± 2, 32 ± 2, and 49 ± 2 g/L d-arabitol from 70, 105, and 150 g/L xylose, respectively. In addition, we found that R. toruloides could potentially be used for the co-production of lipids and d-arabitol from xylose. These results demonstrate that R. toruloides can be used to produce multiple value-added chemicals from xylose. [ABSTRACT FROM AUTHOR]

Ice-nucleating particles (INPs) active at modest supercooling (e.g. -8 °C; INP-8/ can transform clouds from liquid to mixed phase, even at very small number concentrations (<10m-3/. Over the course of 15 months, we found very similar patterns in weekly concentrations of INP-8 in PM10 (median D1.7m-3, maximum D10.1m-3/ and weekly amounts of rainfall (median D28 mm, maximum D153 mm) at Birkenes, southern Norway. Most INP-8 were probably aerosolised locally by the impact of raindrops on plant, litter and soil surfaces. Major snowfall and heavy rain onto snow-covered ground were not mirrored by enhanced numbers of INP-8. Further, transport model calculations for large (>4m-3/ and small (<4m-3/ numbers of INP-8 revealed that potential source regions likely to provide precipitation to southern Norway were associated with large numbers of INP-8. The proportion of land cover and land use type in potential source regions was similar for large and small numbers of INP-8. In PM2:5 we found consistently about half as many INP-8 as in PM10. From mid-May to mid-September, INP-8 correlated positively with the fungal spore markers arabitol and mannitol, suggesting that some fraction of INP-8 during that period may consist of fungal spores. In the future, warmer winters with more rain instead of snow may enhance airborne concentrations of INP-8 during the cold season in southern Norway and in other regions with a similar climate. [ABSTRACT FROM AUTHOR]

In the present study, a novel ardh gene encoding d -arabitol dehydrogenase (ArDH) was cloned and expressed in Escherichia coli from a new isolated strain of Gluconobacter sp. JX-05. Sequence analysis revealed that ArDH containing a NAD(P)-binding motif and a classical active site motif belongs to the short-chain dehydrogenase family. Subsequently, the optimal pH and temperature, specific activities and kinetic parameter of ArDH were determined. In the co-biotransformation by the whole cells of BL21- ardh and BL21- xdh , 26.1 g/L xylitol was produced from 30 g/L d -arabitol in 22 h with a yield of 0.87 g/g. The xylitol production was increased by more than two times as compared with that of Gluconobacter sp. alone, and was improved 10.1% than that of Gluconobacter sp. mixed with BL21- xdh . [ABSTRACT FROM AUTHOR]

In this work, three monomeric forms of arabinitol, usually named arabitol, and their dimeric species have been structural and vibrationally studied by using the micro-Raman spectra in the solid phase accomplished with theoretical calculations based on the theory of the functional of the density (DFT). The hybrid B3LYP method was used for all the calculations together with the 6-31G* and 6-311++g** basis sets. Two different L structures with minima energies were predicted in accordance to the two polymorphic structures revealed by recent X-ray diffraction experiments. The studies by natural bond orbital (NBO) calculations reveals high stabilities of the L form as compared with the D one but the topological properties by using the atoms in molecules (AIM) suggest a higher stability of the D form due to a strong H bond interactions. The scaled mechanical force fields (SQMFF) procedure was used to perform the complete vibrational assignments for the monomeric forms and their dimer. On the other hand, the similarity in the gap values computed for the three forms of arabitol with those observed for sucrose, trehalose, maltose and lactose in gas phase at the same level of theory could partially explain the sweetening property of this alcohol. In addition, the influences of the size of the basis set on some properties were evidenced. [ABSTRACT FROM AUTHOR]

Meyerozyma caribbica strain 5XY2, which was isolated from an alcohol fermentation starter in Thailand, was found to catabolize l -arabinose as well as d -glucose and d -xylose. The highest production amounts of ethanol from d -glucose, xylitol from d -xylose, and l -arabitol from l -arabinose were 0.45 g/g d -glucose, 0.60 g/g d -xylose, and 0.61 g/g l -arabinose with 21.7 g/L ethanol, 20.2 g/L xylitol, and 30.3 g/l l -arabitol, respectively. The enzyme with l -arabitol dehydrogenase (LAD) activity was purified from the strain and found to exhibit broad specificity to polyols, such as xylitol, d -sorbitol, ribitol, and l -arabitol. Xylitol was the preferred substrate with K m = 16.1 mM and k cat / K m = 67.0 min −1 mM −1 , while l -arabitol was also a substrate for the enzyme with K m = 31.1 mM and k cat / K m = 6.5 min −1 mM −1 . Therefore, this enzyme from M. caribbica was named xylitol dehydrogenase ( Mc XDH). Mc XDH had an optimum temperature and pH at 40°C and 9.5, respectively. The Mc XDH gene included a coding sequence of 1086 bp encoding a putative 362 amino acid protein of 39 kDa with an apparent homopentamer structure. Native Mc XDH and recombinant Mc XDH exhibited relative activities toward l -arabitol of approximately 20% that toward xylitol, suggesting the applicability of this enzyme with the functions of XDH and LAD to the development of pentose-fermenting Saccharomyces cerevisiae . [ABSTRACT FROM AUTHOR]

The conversion of hemicellulosic biomass to sugar alcohols commonly applies homogeneous acids and noble metals as catalysts, which is neither economical nor environmentally friendly. In order to overcome the deficiencies of the reports, a series of non-precious catalysts were synthesized through the co-precipitation method and incipient wetness impregnation (IWI) method in converting hemicellulosic biomass, i.e., hemicellulose and xylose into sugar alcohols (i.e., xylitol and arabitol). Reaction experiments showed that the Ni 8.98 Fe 1 @ 1.54SiO 2 catalyst prepared by the IWI method has excellent catalytic performance for converting xylose to sugar alcohols in the neutral aqueous solution, and can be applied to the direct conversion of hemicellulose as well. Specifically, the optimum yield of xylitol and arabitol could obtain 99.48 mol% and 26.01 mol% for xylose as the substrate and 88.16 mol% and 20.55 mol% for hemicellulose as the substrate, respectively. Characterization techniques such as X-ray diffraction (XRD), N 2 adsorption-desorption isotherm, transmission electron microscopy (TEM), scanning electron microscope (SEM), H 2 temperature-programmed reduction (H 2 -TPR), NH 3 temperature-programmed desorption (NH 3 -TPD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy of pyridine (Py-FTIR), and SQUID vibrating sample magnetometry (SQUID -VSM) were performed to study physicochemical properties of the catalyst. N 2 adsorption-desorption isotherm and NH 3 -TPD characterizations indicated that the catalyst with mesoporous properties and proper acidic sites is vital for hydrolyzing hemicellulose to pentose (i.e., xylose and arabinose). TEM, H 2 -TPR, and XPS techniques revealed that the (111) plane of metallic Ni is the main active phase for the hydrogenation of pentose into sugar alcohols, and Fe2+ and Fe3+ species act as effective promoters to enhance the pentose hydrogenation. Py-FTIR characterization and reaction conditions indicated that the appropriate ratio of Brønsted to Lewis acidic sites could facilitate the conversion of xylose to arabitol. The reaction mechanisms for converting hemicellulosic biomass to sugar alcohols were proposed based on the systematic study of reaction conditions and characterizations. N 2 adsorption-desorption, H 2 -TPR, and XPS indicated that the catalyst with strong metal-support interaction, large specific surface area and pore volume could be beneficial for catalytic stability, which is verified in leaching and reusability tests. The catalyst has superparamagnetic, which can be quickly separated from the reaction system under the external magnetic field, facilitating the recovery and utilization of the catalyst. [Display omitted] • Hemicellulose is efficiently converted to xylitol and arabitol by Ni 8.98 Fe 1 @1.54SiO 2. • The catalyst with mesoporous and proper acidity favors hemicellulose hydrolysis. • The catalyst with Ni0, Fe2+/3+, and proper B/L is beneficial for xylose to pentitol. • The mechanisms are proposed based on systematic reactions and characterizations. • The catalyst is stable and can be separated from the liquor by the magnetic field. [ABSTRACT FROM AUTHOR]

Lactic acid is the monomer unit of the bioplastic poly-lactic acid (PLA). One candidate organism for lactic acid production is Pichia pastoris, a yeast widely used for heterologous protein production. Nevertheless, this yeast has a poor fermentative capability that can be modulated by controlling oxygen levels. In a previous study, lactate dehydrogenase (LDH) activity was introduced into P. pastoris, enabling this yeast to produce lactic acid. The present study aimed to increase the flow of pyruvate towards the production of lactic acid in P. pastoris. To this end, a strain designated GLp was constructed by inserting the bovine lactic acid dehydrogenase gene (LDHb) concomitantly with the interruption of the gene encoding pyruvate decarboxylase (PDC). Aerobic fermentation, followed by micro-aerophilic culture two-phase fermentations, showed that the GLp strain achieved a lactic acid yield of 0.65 g/g. The distribution of fermentation products demonstrated that the acetate titer was reduced by 20% in the GLp strain with a concomitant increase in arabitol production: arabitol increased from 0.025 g/g to 0.174 g/g when compared to the GS115 strain. Taken together, the results show a significant potential for P. pastoris in producing lactic acid. Moreover, for the first time, physiological data regarding co-product formation have indicated the redox balance limitations of this yeast.

Bacterial cellulose (BC) exhibits beneficial properties for use in biomedical applications but is limited by its lack of tunable transparency capabilities. To overcome this deficiency, a novel method to synthesize transparent BC materials using an alternative carbon source, namely arabitol, was developed. Characterization of the BC pellicles was performed for yield, transparency, surface morphology, and molecular assembly. Transparent BC was produced using mixtures of glucose and arabitol. Zero percent arabitol pellicles exhibited 25% light transmittance, which increased with increasing arabitol concentration through to 75% light transmittance. While transparency increased, overall BC yield was maintained indicating that the altered transparency may be induced on a micro-scale rather than a macro-scale. Significant differences in fiber diameter and the presence of aromatic signatures were observed. Overall, this research outlines methods for producing BC with tunable optical transparency, while also bringing new insight to insoluble components of exopolymers produced by Komagataeibacter hansenii., Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jeannine M. Coburn, Elizabeth M. van Zyl, and Eric M. Young have the patent Transparent Cellulose-Based Materials and Methods of Making the Same pending to Worcester Polytechnic Institute., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Kinetics of isothermal crystallization of l -arabitol were analyzed from the undercooled liquid state within micron-sized droplets from micro-Raman spectroscopy. This study reveals that crystallization slightly above T g is controlled by stochastic heterogeneous nucleation inherent to the droplet size. Microscopic Raman investigations performed in droplets give the unique opportunity to analyze the pure metastable Form II of l -arabitol. It was found that Form II is characterized by a molecular packing more compact than that of the stable Form I, inherent to strong intermolecular hydrogen bonding. Kinetics laws obtained by analyzing several droplets at different temperatures, reveal the transient character of Form II, quasi systematically detected during the crystallization process of form I. Form II appears as the first step of crystallization prior to successive short-living metastable states which is necessary to achieve a complete crystallization in Form I. It was found that the kinetics of conversion between the metastable states (Form II) into Form I is dependent on the amount of strong hydrogen bonding distinctive of Form II. [ABSTRACT FROM AUTHOR]

Reductive catalytic splitting to sugar alcohols is a promising technology to valorize (hemi)cellulosic feedstock. This contribution focuses on the conversion of arabinoxylan (AX), a common hemicellulose polymer, to pentitols like xylitol and arabitol in the presence of ruthenium-loaded H-USY zeolites. Both acid and metal sites on the catalyst play a crucial role in the bifunctional catalytic mechanism. Overall, the reaction mechanism involves hydrolysis of AX into shorter (less reactive) xylan oligomer intermediates (XOs), which are in turn hydrolysed into sugar monomers. The first step occurs fast in hot liquid water, but the second step which is rate limiting, requires acid catalysis. Literature has reported successful XO hydrolysis with soluble acids. However, USY zeolites, being non-corrosive instead of the former, are able to hydrolyse XOs more efficiently, likely due to their strong mesopore adsorption capacity. Once formed, the monomeric sugars should be hydrogenated on the metal sites as fast as possible, as otherwise undesired competitive acid catalysed side-reactions will occur. While another catalyst like Ru on carbon can also be used in the one-pot approach close proximity of the two sites, e.g. in the pores of the USY zeolite, is beneficial for the pentitol selectivity, as long as they are well harmonised. After searching for the ideal dual site balance, exceptionally high pentitol yields up to 90 mol% were achieved after only 5 h of reaction. Comparison with earlier reported cellulose reactions shows a narrowing of the ideal acid-to-metal range, besides a shift to lower ratios. Initial regeneration studies show a stable Ru/USY catalytic system able to perform multiple reaction runs with retention of activity and selectivity. [ABSTRACT FROM AUTHOR]

Transposon insertion into Listeria monocytogenes lmo2665, which encodes an EIIC of the phosphoenolpyruvate:carbohydrate phosphotransferase system (PTS), was found to prevent D -arabitol utilization. We confirm this result with a deletion mutant and show that Lmo2665 is also required for D - xylitol utilization. We therefore called this protein EIIC Axl. Both pentitols are probably catabolized via the pentose phosphate pathway (PPP) because lmo2665 belongs to an operon, which encodes the three PTS Axl components, two sugar-P dehydrogenases, and most PPP enzymes. The two dehydrogenases oxidize the pentitol-phosphates produced during PTS-catalyzed transport to the PPP intermediate xylulose-5-P. L. monocytogenes contains another PTS, which exhibits significant sequence identity to PTSAxl . Its genes are also part of an operon encoding PPP enzymes. Deletion ofthe EIIC-encoding gene (lmo0508) affected neither D -arabitol nor D -xylitol utilization, although D -arabitol induces the expression of this operon. Both operons are controlled by MtlR/LicR-type transcription activators (Lmo2668 and Lmo0501, respectively). Phosphorylation of Lmo0501 by the soluble PTSAxl components probably explains why D -arabitol also induces the second pentitol operon. Listerial virulence genes are submitted to strong repression by PTS sugars, such as glucose. However, D -arabitol inhibited virulence gene expression only at high concentrations, probably owing to its less efficient utilization compared to glucose. [ABSTRACT FROM AUTHOR]

An elevated concentration of d -arabitol in urine, especially compared to that of l -arabitol or creatinine, is indicative of a fungal infection. For that purpose, we devised, fabricated, and tested chemical sensors determining d -arabitol. These chemosensors comprised the quartz crystal resonator (QCR) or extended-gate field-effect transistor (EG-FET) transducers integrated with molecularly imprinted polymer (MIP) film recognition units. To this end, we successfully applied a covalent approach to molecular imprinting, which involved formation of weak reversible covalent bonds between vicinal hydroxyl groups of arabitol and boronic acid substituents of the bithiophene functional monomer used. The MIP films were synthesized and simultaneously deposited on gold electrodes of quartz crystal resonators (Au-QCRs) or Au-glass slides by oxidative potentiodynamic electropolymerization. With the QCR and EG-FET chemosensors, the d -arabitol concentration was determined under flow-injection analysis and stagnant-solution binding conditions, respectively. Selectivity with respect to common interferences, and l -arabitol in particular, of the devised chemosensors was superior. Limits of detection and linear dynamic concentration ranges of the QCR and EG-FET chemosensors were 0.15 mM and 0.15 to 1.25 mM as well as 0.12 mM and 0.12 to 1.00 mM, respectively, being lower than the d -arabitol concentrations in urine of patients with invasive candidiasis (>220 μM). Therefore, the devised chemosensors are suitable for early diagnosis of fungal infections caused by Candida sp. yeasts. [ABSTRACT FROM AUTHOR]