Search

To valorize crustacean shells, an aquatic organism‐derived food waste, this study was conducted to synthesize 5‐hydroxymethylfurfural (5‐HMF) and levulinic acid (LA) from d‐glucosamine (GlcN) and N‐acetyl‐d‐glucosamine (GlcNAc) using a Lewis acid (ZrCl4) as a catalyst. The Box–Behnken statistical approach was used to optimize the reaction conditions and to analyze the reciprocal relationships between reaction parameters. In the GlcN conversion, the highest LA yield of 38.4% was obtained under a condition with 200 °C for 25 min with 0.35 M GlcN and 25 mol% catalyst/substrate. However, in GlcNAc conversion, the highest 5‐HMF yield of 9.75% was obtained at 175 °C for 20 min with 0.2 mol L−1 GlcNAc and 15 mol% catalyst/substrate. Under the same reaction conditions, a higher yield of LA was obtained from GlcN compared with GlcNAc. It seems that GlcN can be transformed into 5‐HMF and then further rehydrated to LA more readily than GlcNAc. These findings suggest that GlcN and GlcNAc derived from crustacean shells may be an accessible feedstock for the synthesis of valuable chemical compounds. [ABSTRACT FROM AUTHOR]

Background: Acid‐catalyzed hydrothermal conversion can be considered one of the most effective methods for converting agricultural wastes into sustainable and renewable fuels and value‐added chemicals. Orange wastes are a potential renewable and sustainable resource for the synthesis of value‐added compounds because of their high organic matter content. In this study, acid‐catalyzed hydrothermal conversion of orange peel was applied to produce levulinic acid (LA) using a statistical experimental approach. Results: The reaction conditions for LA synthesis by sulfuric acid‐catalyzed hydrothermal conversion of orange peel was optimized at middle‐to‐high temperatures, low catalyst concentrations, and prolonged reaction times within the tested ranges. As a result, an LA yield of 17.13 wt% (biomass weight basis) or 60.77% (glucan content basis) was achieved under the condition of 185 °C, 10% biomass, 0.3 mol L−1 sulfuric acid, and 30 min. In the relationship between combined severity (CS) and LA yield, LA yield increased moderately with increasing CS value until CS 3.2, then remained stable. The highest LA yield was observed under the CS 3.7 condition. Conclusion: The findings of this study demonstrated the potential value of orange peel as a renewable agricultural waste for the manufacture of valuable chemicals and materials. © 2023 Society of Industrial Chemistry and John Wiley & Sons Ltd. [ABSTRACT FROM AUTHOR]

• One-pot LA synthesis from macroalgae by ionic resin-catalyzed hydrothermal conversion. • 30.3 % LA yielded at 200 °C and 90 min with 12.5 % biomass and 50 % catalyst/biomass. • The use of Purolite CT269DR presents significant potential for the synthesis of LA. • The relationship between CS and LA synthesis was matched to the sigmoidal equation. Gracilaria verrucosa is red algae (Rhodophyta) that is particularly significant because of its potential for bioenergy production as a sustainable and environmentally friendly marine bioresource. This study focuses on the production of levulinic acid from G. verrucosa using hydrothermal conversion with an ionic resin Purolite CT269DR as the catalyst. By optimization of the conversion condition, a 30.3 % (22.58 g/L) yield of levulinic acid (LA) (based on carbohydrate content) was obtained at 200 °C for 90 min with 12.5 % biomass and 50 % catalyst loading of biomass quantity. Simultaneously, formic acid yielded 14.0 % (10.42 g/L). The LA yield increased with increasing combined severity (CS) levels under tested ranges. Furthermore, the relationship between CS and LA synthesis was effectively fitted to the nonlinear sigmoidal equation. However, as the yield of sugar decreased, LA yield was linearly increased. Thus, the use of ionic resin as a heterogeneous catalyst presents significant potential for the manufacture of platform chemicals, specifically LA, through the conversion of renewable marine macroalgae. [ABSTRACT FROM AUTHOR]

Due to increased coffee consumption, spent coffee grounds (SCG) are an ever-growing waste management concern, despite the opportunity to recycle and reuse this valuable bioresource. SCG is an attractive feedstock for the production of bio-based compounds due to its high carbohydrate content and availability. This study developed the thermochemical conversion using an acid catalyst for the production of valuable platform chemicals (levulinic acid and formic acid) from lipid-extracted SCG. Conversion condition was optimized using statistical methodology and the reciprocal interactions between the reaction factors were analyzed. As a consequence of optimizing conversion conditions, the maximum yields of levulinic acid and formic acid were achieved at 190 °C, 10 % lipid-extracted SCG, 0.4 M sulfuric acid, and 60 min: 15.6 % and 7.73 %, respectively, based on biomass weight. Furthermore, in the reciprocal interactions of reaction factors, larger LA yields were achieved when the temperature was elevated, the catalyst concentration was decreased, and the reaction time was prolonged under the experimental ranges. According to these findings, lipid-extracted SCG has high potential as a sustainable and renewable feedstocks for the synthesis of bio-based platform chemicals in the biorefinery sector. • SCG is an attractive substrate for the synthesis of bio-based compounds. • 15.6 % levulinic acid yield at 190 °C, 10.0 % biomass, 0.4 M sulfuric acid, and 60 min. • Carbohydrates in SCG may be exploited as a bioresource for bio-based platform chemicals. • Larger LA yields were elevated temperature, less catalyst concentration, and prolonged time. [ABSTRACT FROM AUTHOR]

In this study, the hydrolysis of marine macro-algae Gracilaria verrucosa with a solid-acid catalyst was investigated. To optimize the hydrolysis, four reaction factors, including liquid-to-solid ratio, catalyst loading, reaction temperature, and reaction time, were investigated. In the results, the highest total reducing sugar (TRS) yield, 61 g/L (51.9%), was obtained under the following conditions: 1:7.5 solid-to-liquid ratio, 15% (w/v) catalyst loading, 140 °C reaction temperature, and 150 min reaction time. Under these conditions, 10.7 g/L of 5-HMF and 2.5 g/L of levulinic acid (LA) were generated. The application of solid-acid catalyst and marine macro-algae resources shows a very high potential for production of fermentable sugars. [ABSTRACT FROM AUTHOR]

In this study, the efficient conversion of Helianthus tuberosus L. (Jerusalem artichoke) to sugar, 5-hydroxymethylfurfural (5-HMF), and levulinic acid (LA) were investigated using a Brønsted acid-catalyzed hydrothermal reaction. From this approach, the optimal amounts and reaction conditions for total reducing sugar (TRS), 5-HMF, and LA were as follows: 444 g kg −1 of TRS yield (150.4 °C, 14.6 kg m −3 sulfuric acid, and 9.8 min), 193 g kg −1 of 5-HMF yield (166.0 °C, 4.6 kg m −3 , 30.8 min), and 323 g kg −1 of LA yield (185 °C, 30.8 kg m −3 , 33.7 min). In terms of combined severity, the TRS and 5-HMF concentrations decreased linearly with increasing combined severity, whereas, the LA concentration was increased at a high combined severity factor. The H. tuberosus L. may be useful as a significant feedstock for the production of platform chemicals such as 5-HMF and LA. [ABSTRACT FROM AUTHOR]

Glucosamine is a basic unit of the chitin/chitosan structure, which is derived from crustacean (e.g. crab, shrimp) and insect shells. In this study, the production of levulinic acid (LA) from glucosamine via dilute-acid-catalyzed hydrothermal hydrolysis was investigated. Among the reaction conditions, reaction temperature, reaction time, and substrate concentration were more effective than catalyst concentration. The optimal conditions for LA production, as determined by the response-surface methodology (RSM), were as follows: 188 °C reaction temperature, 4 wt% catalyst concentration, 49 min reaction time, 120 g/L substrate concentration. Under these conditions, the LA yield was 30.3 g/L (25.3 wt%), while the 5-HMF concentration was zero. These results might provide basic knowledge essential to the production of valuable chemicals derivable from renewable marine resources and utilizable as fuel additives and polymer building blocks. [ABSTRACT FROM AUTHOR]

Microalgae are known as renewable, potential, and sustainable feedstocks for biofuel production. The present work investigated the efficient valorization of green microalgae Chlorella sp. to produce sugars and 5-hydroxymethylfurfural (5-HMF) using thermochemical conversion with a metal-salt (ferric sulfate) as catalyst using a statistical approach and two-step conversion. A statistical approach with a Box–Behnken design was introduced to optimize the conversion for producing sugars. As a result of optimization, 86.46% sugar yield (68.32% glucose yield) was achieved under the condition of 5% biomass and 0.6 g-catalyst/g-biomass at 155 °C and 40 min. Two-step thermochemical conversion was introduced to produce 5-HMF from microalgae. In the first step, sugars were produced from the above optimum condition; in the second step, sugar hydrolysates were converted into 5-HMF by thermochemical conversion without an additional catalyst. In two-step conversion, the maximum 5-HMF yield (37.23%) was achieved at 170 °C and 60 min from the sugar hydrolysate of microalgae obtained from the first-step thermochemical conversion with ferric sulfate. In conclusion, the microalgae as biomass and ferric sulfate as catalyst have availability and the potential to produce biosugars and platform chemicals. • Efficient valorization of C hlorella sp. to sugars and 5-HMF using thermochemical conversion with ferric sulfate. • 86.46% sugar (68.32% glucose) yields were under 5% biomass and 0.6 g-catalyst/g-biomass at 155 °C and 40 min. • In two-step conversion, the maximum 5-HMF yield (37.23%) was achieved at 170 °C and 60 min from the sugar hydrolysate. • Microalgae and ferric sulfate have availability and the potential to produce biosugars and platform chemicals. [ABSTRACT FROM AUTHOR]

Microalgae are renewable, eco-friendly, and sustainable bioresources that have the potential to substitute fuels and chemicals originated fossil resources. The conversion of Chlorella sp. to obtain 5-hydroxymethylfurfural (5-HMF) and levulinic acid (LA) via thermochemical reaction with a metal-sulfate catalyst (Al 2 (SO 4) 3) is introduced here. The statistical approach is introduced to optimize the conversion conditions. By optimization of the 5-HMF yield, about 23.46% of 5-HMF was obtained under 5% biomass amount and 0.75 g-catalyst/g-biomass at 165 °C and 30 min; the highest LA yield of 32.89% was obtained under 2.5% biomass and 1.0 g-catalyst/g-biomass at 205 °C and 60 min. Furthermore, under such harsh temperature condition and high catalyst amount, the maximum 5-HMF yield of 31.46% was obtained at 0 min, which indicates the time required to attain the set reaction temperature. In the evaluation of the catalytic performance via relationship between combined severity factor and 5-HMF/LA, the yields of 5-HMF and LA were demonstrated to be reasonably satisfied for non-linear sigmoidal equations with high regression. Hence, the application of microalgae and metal-salt catalyst has high potential and accessibility in the production of platform chemicals. • Efficient hydrothermal conversion of C hlorella sp. into 5-HMF and LA by metal sulfate catalyst. • 23.46% 5-HMF was obtained under 5% biomass, 0.75 g-catalyst/g-biomass at 165 °C and 30 min. • 32.89% LA was obtained under 2.5% biomass, 1.0 g-catalyst/g-biomass at 205 °C and 60 min. [ABSTRACT FROM AUTHOR]

Microalgae are potential alternative resources that can replace fossil resources for the production of biofuels and chemicals. Levulinic acid (LA) and formic acid (FA) were produced from defatted Scenedesmus obliquus (a green microalga) via sulfuric acid-catalyzed thermochemical conversion using Box-Behnken design. Following optimization, 39.93% LA and 25.82% FA yields were obtained with 5 wt% biomass concentration and 0.8 M H 2 SO 4 as the catalyst at 180 °C for 40 min. Furthermore, LA and FA yields matched well with a non-linear sigmoidal equation with the combined severity factor (CSF). High LA and FA yields were achieved at a CSF > 10.4. The results demonstrated the potential of microalgae as a biomass and Brönsted acid as a catalyst for producing platform chemicals. [ABSTRACT FROM AUTHOR]

• Levulinic acid produced under acid-catalyzed thermochemical conversion. • Lipid-extracted microalgae S. obliquus is available resource for producing LA. • 45.63% LA yield achieved under 5 wt% biomass, 0.85 M HCl at 180 °C for 10 min. • Lipid-extracted microalgae has potential for production of platform chemicals. • LA yields to CSF properly match a non-linear sigmoidal equation. Scenedesmus obliquus , a green microalga of the class Chlorophyceae, has been used to produce biofuels. However, limited research has been reported on platform chemicals that use microalgae as biomass to replace fossil sources. This paper reports on the investigation of levulinic acid (LA) production from lipid-extracted S. obliquus with an acid-catalyzed thermochemical conversion using a statistical experimental approach. For the reaction factors, the highest effect on LA yield resulted from catalyst concentration. The optimized LA yield of 45.63 wt% (70.7 mol%) was achieved with 5 wt% lipid-extracted microalgae and reaction factors of 0.85 M HCl as a catalyst at 180 °C for 10 min. Also, the LA yield as a function of the combined severity factor followed a sigmoid curve. High LA yield resulted from combined severity factors greater than 3.4. These results indicate that the production of platform chemicals may be possible using microalgae feedstocks and thermochemical conversion. [ABSTRACT FROM AUTHOR]

• Red wavelength is effective for biomass production in Nannochloris atomus. • The optimized Nannochloris atomus produced the highest biomass of 1.15 g/L on day 12. • Nannochloris atomus has enhanced lipid production under stress conditions. • Nannocholris atomus produced 1.8 times higher lipid in 1.06 M NaCl and green stress. • The main fatty acid in Nannochloris atomus is linolenic acid. The optimal conditions for high biomass and lipid production from Nannochloris atomus were evaluated. The parameters used in this study were light emitting diode (LED) wavelength mixing ratio, the photoperiod, salinity tolerance, and single and combined stresses. Biomass production was monitored in the first phase using red LED (625 nm), followed by lipid production by green LED (520 nm) in the second phase. The optimal conditions were obtained using a single red LED with light:dark durations of 20:4 h and two days of exposure in combined stresses of 1.06 M NaCl and green LED. Under these conditions, 68.6 % (w/w) lipid content were obtained. Compared to the non-stress control, the lipid content was increased by 31.9 %. Linolenic acid (C18:3) the omega-3 fatty acid was produced up to 52.4 % in 1.06 M NaCl as a single stress. [ABSTRACT FROM AUTHOR]

The seaweed industry has developed rapidly over the last decade, and carrageenan is the leading hydrocolloid in the seaweed industry. Approximately 57,500 t of carrageenan is produced annually throughout the world. As a consequence of the increase in carrageenan production, the enormous amount of waste resulting from the carrageenan industry has also increased. This study investigated the possibility of ethanol production using carrageenan solid waste from the carrageenan extraction of Kappaphycus alvarezii, the principal species used in the carrageenan industry. Optimum acid hydrolysis followed by enzymatic hydrolysis enhanced the production of both galactose and glucose. Fermentation of the enzymatic hydrolysate using Saccharomyces cerevisiae ATCC 200062 resulted in an ethanol yield of 13.8 g L−1. [ABSTRACT FROM AUTHOR]

Being an agarophyte, Gelidium is extensively exploited for its agar-producing capacity. However, the food value and medicinal importance of this red alga are not to be underestimated. The pharmacological properties of Gelidium species have potential for the pharmaceutical, nutraceutical and cosmeceutical industries. This review collects, identifies and analyzes comprehensively the studies that deal with the bioactive properties of Gelidium species in the last decade. The principal bioactive compounds of Gelidium include R-phycoerythrin, R-phycocyanin, alkaloids, terpenoids, tannins, flavonoids, saponins, coumarins, cardiac glycosides, and steroids. Gelidium in the form of extracts or isolated compounds have been reported to show antibacterial, antioxidant, anticancer, anti-inflammatory, anti-obesity, immunomodulatory, neuroprotective, and antidiabetic properties. Most of the evidence has been reported in various in vitro models. Therefore, further experiments using appropriate animal and human subjects are necessary to develop the preclinical findings into clinical use. The main challenge in developing bioactive compounds on a commercial scale is the sustainable supply of Gelidium biomass that requires integrated seaweed aquaculture through employing biotechnological approaches and effective utilization of industrial byproducts. [ABSTRACT FROM AUTHOR]

In this study, sulfamic acid-catalyzed pretreatment and subsequent enzymatic hydrolysis was conducted to produce biosugar from the marine macro-alga Gracilaria verrucosa. Sulfamic acid has dual active sites and is a green catalyst. Optimized sulfamic acid pretreatment at 130°C with 7.5% biomass and 100 mM sulfamic acid for 90 min yielded 39.9% total reducing sugar (TRS). Subsequent enzymatic hydrolysis yielded 69.1% TRS. These results indicate the potential of sulfamic acidcatalyzed pretreatment and subsequent enzymatic hydrolysis in producing biosugars using a biorefinery process. [ABSTRACT FROM AUTHOR]

Blue and red light-emitting diodes (LEDs) were used to study the effects of wavelength mixing ratios, photoperiod regimes, and green wavelength stress on Nannochloropsis salina , Isochrysis galbana , and Phaeodactylum tricornutum cell biomass and lipid production. The maximum specific growth rates of I . galbana and P . tricornutum were obtained under a 50:50 mixing ratio of blue and red wavelength LEDs; that of N . salina was obtained under red LED. Maximum cell biomass for N . salina and P . tricornutum was 0.75 and 1.07 g dcw/L, respectively, obtained under a 24:0 h light/dark cycle. However, the maximum I . galbana biomass was 0.89 g dcw/L under an 18:6 h light/dark cycle. The maximum lipid contents for N . salina, I . galbana , and P . tricornutum were 49.4, 63.3 and 62.0% (w/w), respectively, after exposure to green LED. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were obtained 1% in P . tricornutum and 2% in I . galbana . [ABSTRACT FROM AUTHOR]

In this study, the parameters of microalga culture were optimized to maximize the biomass and lipid production of Chlamydomonas hedleyi. Experiments were performed using a two-phase culture system. In the first phase, the nitrate concentration, LED photoperiod, and light intensity were optimized for maximal biomass production. In the second phase, the LED photoperiod and light intensity under nitrate starvation conditions were optimized to induce maximal lipid production. During the first phase of culture, a biomass of 0.95 g DCW/L and the shortest cultivation time were obtained with a nitrate concentration of 240 mg/L, under a 24:0 h light:dark cycle, and a light intensity of 500 µmol m−2 s−1. In the second phase of culture, a maximum lipid content of 41.3% was obtained with a light:dark cycle of 12:12 h and a light intensity of 400 µmol m−2 s−1 under nitrate starvation conditions for 2 days. C. hedleyi lipids meet international biodiesel standards, such as cetane number, iodine value, and oxidative stability. This study contributes to the related literature by providing information on C. hedleyi and evaluating its potential as a biodiesel feedstock. [Display omitted] • Two-phase culture can improve biomass and lipid production of Chlamydomonas hedleyi. • The productivity of C. hedleyi was optimized using light emitting diodes. • Combined stress can induce maximal lipid production in C. hedleyi. • The lipid composition of C. hedleyi meets most international biodiesel standards. [ABSTRACT FROM AUTHOR]

The physiological characteristics and the potential gluconolactone production of the gluconolactonase-deficient strain, Zymomonas mobilis ZM4 gnlΔ, were investigated via growth inhibitory assay and biotransformation of glucose and fructose into gluconolactone and sorbitol, respectively. The results of ethanol fermentation studies performed in the presence of high concentration of glucose (>200 g l) under fermentative or aerobic conditions indicated that a significant reduction of volumetric ethanol productivity from the strain of ZM4 gnlΔ was noticeable due to the reduced rates of specific growth, sugar uptake, and biomass yield as compared with those of the parental strain ZM4. The biotransformation prepared at pH 6.0 using the permeabilized cell indicated that gluconic acid from ZM4 gnlΔ was still produced as a major product (67 g l) together with sorbitol (65 g l) rather than gluconolactone after 24 h. Only small amount of gluconolactone was transiently overproduced up to 9 g l, but at the end of biotransformation, all gluconolactone were oxidized into gluconic acid. This indicated that autolysis of gluconolactone at the pH led to such results despite under gluconolactonase inactivation conditions. The physiological characteristics of ZM4 gnlΔ was further investigated under various stress conditions, including suboptimal pH (3.5~6.0), temperature (25~40 °C), and presence of growth inhibitory molecules including hydrogen peroxide, ethanol, acetic acid, furfural, and so forth. The results indicated that ZM4 gnlΔ was more susceptible at high glucose concentration, low pH of 3.5, and high temperature of 40 °C and in the presence of 4 mM HO comparing with ZM4. Therefore, the results were evident that gluconolactonase in Z. mobilis contributed to industrial robustness and anti-stress regulation. [ABSTRACT FROM AUTHOR]

Hyper thermal (HT) acid hydrolysis of Kappaphycus alvarezii , a red seaweed, was optimized to 12% (w/v) seaweed slurry content, 180 mM H 2 SO 4 at 140 °C for 5 min. The maximum monosaccharide concentration of 38.3 g/L and 66.7% conversion from total fermentable monosaccharides of 57.6 g/L with 120 g dw/L K. alvarezii slurry were obtained from HT acid hydrolysis and enzymatic saccharification. HT acid hydrolysis at a severity factor of 0.78 efficiently converted the carbohydrates of seaweed to monosaccharides and produced a low concentration of inhibitory compounds. The levels of ethanol production by separate hydrolysis and fermentation with non-adapted and adapted Kluyveromyces marxianus to high concentration of galactose were 6.1 g/L with ethanol yield ( Y EtOH ) of 0.19 at 84 h and 16.0 g/L with Y EtOH of 0.42 at 72 h, respectively. Development of the HT acid hydrolysis process and adapted yeast could enhance the overall ethanol fermentation yields of K. alvarezii seaweed. [ABSTRACT FROM AUTHOR]

To provide an option for the reutilization of high-salinity anchovy fishmeal wastewater (FMW), generated during the anchovy fishmeal manufacturing processes, its potential for biodegradation was assessed in 1-l five-neck flasks using a halotolerant and proteolytic microbial consortium. During the first 41 h of biodegradation, the pH, DO, ORP, and dry-sludge weight decreased as the total cell number of the microbial consortium increased steadily; the COD/TN ratios remained between 4.0 and 5.5, respectively, indicating the stable metabolic degradation of organic matter. The ORP tended to increase after 41 h, and the unpleasant fishy smell disappeared once positive ORP values were achieved. The removal percentages of COD and TN were 59.0 and 54.4 %, respectively, and the dry-sludge weight decreased from 115.5 to 68.0 g, with a degradation rate of 0.59 g h, during the 80 h experiment. The supernatant from the culture of the anchovy FMW at 70 h (culture supernatant) was phytotoxin-free, and the level of total amino acids was 8.04 g 100 g, comparable to that of commercial fertilizers. In hydroponic cultures containing red bean and barley, the culture supernatant demonstrated a good fertilizing ability. The culture supernatant also exhibited a high degree of antioxidant activity, with a 52.3 % hydroxyl radical-scavenging activity and 0.16 reducing power (at OD 700 nm). Moreover, the culture supernatant inhibited DNA damage from hydroxyl radicals, enhancing the reutilization value of anchovy FMW. This report presents the first description of high-salinity anchovy FMW possessing a high reutilization value potential both for agriculture and medicine. [ABSTRACT FROM AUTHOR]

The waste product from salted Undaria pinnatifida (sea mustard) processing was fermented to produce bioethanol by Saccharomyces cerevisiae KCCM 1129 at laboratory and pilot development unit (PDU) scales. Thermal acidic hydrolysis of salted U. pinnatifida was conducted with 75 mM HSO at 121℃ for 60 min and the addition of 1.4 KNU/mL Termamyl 120L. A total monosaccharide concentration of 19.3 g/L and 32.2% conversion from 59.9 g/L total carbohydrate using 130 g dw/L salted U. pinnatifida were achieved. Ethanol fermentations in 5 and 500 L fermenters were carried out to produce 8.5 g/L of ethanol with an ethanol yield (Y) of 0.44 at 24 h and 7.9 g/L with Y of 0.41 at 18 h, respectively. The fermentation time of the PDU-scale reaction was reduced due to differences in the impeller type and geometry of the fermenters. [ABSTRACT FROM AUTHOR]

• Red macroalgae, Gloiopeltis furcata, was used as biomass. • The highest Ep 79.5% value was obtained in thermal acid hydrolysis with HNO 3. • Neither the wild type nor Gal3 overexpression strain could utilize all of the galactose in hydrolysate. • Saccharomyces cerevisiae deleted Gal80 gene could enhance the gene expression related to galactose consumption. Glucose and galactose are monosaccharides obtained from Gloiopeltis furcata (Red algae). A total monosaccharide yield of 62.3 g/L was obtained from G. furcata using thermal acid hydrolysis and enzymatic saccharification. Activated carbon was used to eliminate hydroxymethylfurfural (HMF) from the hydrolysate. Previously obtained monosaccharides are used for ethanol production by Saccharomyces cerevisiae. S. cerevisiae consumes glucose first, then galactose. The methods for reducing fermentation time and increasing the ethanol yield coefficient using the simultaneous consumption of glucose and galactose have been evaluated. Gal3p and Gal80p of S. cerevisiae act as signal transducers that govern the galactose inducer Gal4p mediated transcriptional activation of the Gal gene family. Gal80p binds to Gal4p for transcription deactivation. Therefore, Gal80p was deleted for Gal4p expression without interruption. [ABSTRACT FROM AUTHOR]

• The highest monosaccharide of G. verrucosa was carried out by a R o of 0.47. • The addition of Tween 20 with CTec2 increased the affinity of G. verrucosa with low K m. • A ΔGLK1:ΔMIG1 : ΔMIG2 : TEF2p:PGM2 strain produced 24.8 g/L ethanol (Y EtOH = 0.46). • The adaptation to high concentration of galactose strain produced 24.8 g/L ethanol. • The galactose uptake rate of adapted strain was higher than the engineered strain. Gracilaria verrucosa can be used as a biomass source for bioethanol production with a high yield due to the high carbohydrate content. A monosaccharide concentration of 48.6 g/L was obtained from G. verrucosa using 0.2 M HNO 3 at 150 °C for 10 min with a combined severity factor (R o) of 0.47. The addition of Tween 20 with CTec2 increased the affinity of G. verrucosa slurry to the enzyme with a K m value of 1.14 g/L compared with the K m value of 1.82 g/L using CTec2 alone and reduced enzyme loading. To improve galactose consumption, the deletion of repressor genes including GLK1 , MIG1 , and MIG2 and the overexpression of PGM2 were investigated. The strain with the deletion of three repressor genes and overexpression of PGM2 produced 24.8 g/L ethanol (Y EtOH = 0.46) and showed an enhanced galactose consumption rate (0.24 g/L/h) compared with the rate of the control strain (0.04 g/L/h). The deletion of three repressor genes and overexpression of PGM2 reduced the repression of GAL genes and increased the transcription level of GAL genes. However, the galactose consumption rate of this strain was lower than that of the strain adapted to a high concentration of galactose. [ABSTRACT FROM AUTHOR]

• G. amansii contains 53 μg/g R-phycoerythrin and 56 μg/g R-phycocyanin. • A maximum monosaccharide production of 45.4 g/L (70.7%) was achieved after pretreatment and saccharification of G. amansii. • Fermentation at pH 6.0 supported a high cell growth rate and both glucose and galactose consumption. • The maximum ABE concentration reached 15.5 g/L when pH was shifted from 6.0–4.5. The red seaweed, Gelidium amansii , contains proteins such as R-phycoerythrin and R-phycocyanin, as well as polysaccharides. Initial protein extraction from G. amansii yielded 53 μg/g R-phycoerythrin and 56 μg/g R-phycocyanin. After protein extraction, monosaccharides were produced using hyper thermal acid hydrolysis and enzymatic saccharification. Acetone–butanol–ethanol (ABE) was produced by Clostridium acetobutylicum KCTC 1790. To overcome the different pH requirements for monosaccharide consumption and solvent production, a two-stage pH control culture strategy was developed. Fermentation at pH 6.0 supported a high cell growth rate and both glucose and galactose were consumed completely. The pH was then shifted from 6.0 to 4.5 to produce ABE after 84 h. The maximum ABE concentration reached 15.5 g/L in comparison to 3.1 g/L under fermentation without pH control. The two-stage pH control strategy is a suitable method for ABE production from G. amansii. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Nitrate depletion, salt, and LED wavelengths of second-phase were used for stresses. • Green LED wavelength stress induced the production of microalgal lipid. • The three microalgae, P. tricornutum have high nitrate uptake for cell growth. • The synthesis of fatty acids in microalgae led to form UFAs by stresses. Abstract The effects of wavelengths of light-emitting diode (LED), nitrate concentration, and salt concentration were evaluated for the two-phase culture of the microalgal species Phaeodactylum tricornutum , Dunaliella tertiolecta , and Isochrysis galbana on cell growth and lipid production. Blue LEDs produced the highest biomass of P. tricornutum at a nitrate concentration of 8 mg/L, reaching 0.97 g dcw/L with a specific growth rate (μ) of 0.047 h−1, followed by I. galbana with 0.79 g dcw/L and μ = 0.040 h−1 and D. tertiolecta with 0.55 g dcw/L and μ = 0.028 h−1. Of the three microalgae, P. tricornutum had the highest specific growth rate of μ max = 0.070 h−1 and lowest saturation constant of K s = 4.18 mg/L, resulting in fast cell growth. The highest lipid production was obtained under green LED wavelength stress on day 14, reaching 60.6% (w/w) of the dry cell weight among the three microalgae. The main fatty acids produced by the three microalgae were myristic acid (C14:0), palmitic acid (C16:0), oleic acid (C18:1), and arachidic acid (C20:0), which comprised 72.68%–84.16% (w/w) of the total fatty acids content under three stresses. [ABSTRACT FROM AUTHOR]

Highlights • N. oceanica was cultured in 14-L photobioreactors using a three-phase culture system. • Maximum biomass was produced with 24 h blue LED light at an intensity of 250 µmol m−2 s−1. • Maximum lipid content was obtained with 24 h green LED light at an intensity of 250 µmol m−2 s−1. • SFAs were changed to MUFAs and PUFAs at low temperatures (15, 10, and 5 °C). • The highest PUFA content was obtained at a culture temperature of 5 °C. Abstract A three-phase culture system combining blue (465 nm) light-emitting diode (LED) wavelength as the first phase, green (550 nm) as the second phase, and temperature stress as the third phase was applied to a Nannochloropsis oceanica culture in 14-L photobioreactors. Microalgal growth promotion parameters were optimized in the first phase, followed by green LED stress for lipid production in the second phase. Maximum biomass and lipid production values of 0.75 gdcw L−1 and 57.6% (w/w) were obtained at an aeration rate of 0.50 vvm, with a light intensity of 250 µmol m−2 s−1 and 24:0 h light/dark cycle. Culture temperatures of 15, 10 and 5 °C were applied in the third phase, where temperature stress induced the production of monounsaturated and polyunsaturated fatty acid synthesis in N. oceanica. The production of α-linolenic acid, eicosapentaenoic acid and docosahexaenoic acid increased by 52% (w/w), 96% (w/w), and 77% (w/w), respectively, at 5 °C in the third phase. [ABSTRACT FROM AUTHOR]

Glucosamine is a monomer of chitin/chitosan, which is a renewable aquatic resource and the second most abundant biopolymer on the Earth. Moreover, methanesulfonic acid (MSA) is known as an eco-friendly green catalyst. In this study, the MSA-catalyzed conversion of glucosamine to levulinic (LA) and formic (FA) acids was optimized using the Box-Behnken statistical approach. The optimal conditions for LA yield were 50 g/L glucosamine, 0.5 M MSA, 200 °C and 30 min, which yielded 49.9% LA and 50.8% FA. The LA yield increased linearly with increasing combined severity factor (CSF) until 3.5 and then, was maintained as the CSF value was further increased. The FA yield behaved similarly to LA. Both trends fitted well to a sigmoid regression model with a high regression value. These results highlight the potential of glucosamine for biofuel and chemicals production via an MSA-catalyzed conversion system. [ABSTRACT FROM AUTHOR]

The seaweed genus Gracilaria is a potential candidate for the production of bioethanol due to its high carbohydrate content. Gracilaria is abundant throughout the world and can be found in both wild and cultivated forms. Differences in the ecological factors such as temperature, salinity, and light intensity affecting wild and cultivated specimens may influence the biochemical content of seaweeds, including the carbohydrate content. This study aimed to investigate the proximate composition and potential bioethanol production of wild and cultivated G. gigas and G. verrucosa. Bioethanol was produced using separate hydrolysis fermentation (SHF), employing a combination of enzymatic and acid hydrolysis, followed by fermentation with Saccharomyces cerevisiae ATCC 200062. The highest carbohydrate content was found in wild G. gigas. The highest galactose and glucose contents (20.21 ± 0.32 and 9.70 ± 0.49 g L−1, respectively), as well as the highest production of bioethanol (3.56 ± 0.02 g L−1), were also found in wild G. gigas. Thus, we conclude that wild G. gigas is the most promising candidate for bioethanol production. Further research is needed to optimize bioethanol production from wild G. gigas. Domestication of wild G. gigas is a promising challenge for aquaculture to avoid overexploitation of this wild seaweed resource. [ABSTRACT FROM AUTHOR]

Worldwide, 9600 t of agar is produced annually. Meanwhile, 60% of the waste produced from the agar industry yearly do not get treated. Our present study aims to study the enzymatic saccharification of solid agar waste produced from two of the most widely used agarophytes in the agar industry, Gracilaria verrucosa and Gelidium latifolium. Gracilaria species are the most common raw material in the food grade agar industry, while Gelidium species are the most common raw material used for bacteriological and pharmaceutical purposes because of the high-quality agar that is produced from these species. Our results showed that waste generated from agar extraction still contained sugars which could be optimized by acid pretreatment and enzymatic saccharification. Gracilaria verrucosa resulted in a higher agar yield (35.15 ± 1.17%), but produced less agar waste (20.91 ± 0.43%) than G. latifolium. After sequential acid pretreatment and enzymatic saccharification of the agar waste, the agar waste hydrolysate of G. latifolium resulted in higher glucose, galactose, and ethanol production, and a higher ethanol yield (18.17 ± 0.75, 16.17 ± 2.07, and 10.83 ± 0.30 g L and 0.33 g g, respectively) than G. verrucosa. The results from our present study may be used to optimize biorefinery utilization of G. verrucosa and G. latifolium. [ABSTRACT FROM AUTHOR]

This work investigated the optimization of sugar and chemical formation from marine macro-green-alga Enteromorpha intestinalis by hydrothermal reaction and a statistical methodology. By this approach, the highest sugar and chemical yields were predicted as follows: glucose 10.42 %, xylose-mannose-galactose (XMG) 18.08 %, total reducing sugar (TRS) 28.61 % (reaction temperature 156 °C, catalyst amount 1.3 %, reaction time 11.4 min), levulinic acid 4.00 % (175.0 °C, 3.7 %, 35 min), 5-hydroxymethylfurfural 1.71 % (186.0 °C, 1.1 %, 37.9 min), and furfural 2.03 % (183.1 °C, 2.2 %, 10.7 min). In terms of the combined severity factor (CSF), the glucose, XMG, and TRS production decreased linearly with increasing CSF and to a high correlation. This application of a marine green-alga shows a high potential for production of fermentable sugars and chemicals suitable for biorefinement processes. [ABSTRACT FROM AUTHOR]

The effects of light-emitting diode (LED) wavelength, light intensity, nitrate concentration, and time of exposure to different LED wavelength stresses in a two-phase culture on lipid production were evaluated in the microalga, Picochlorum atomus . The biomass produced by red LED light was higher than that produced by purple, blue, green, or yellow LED and fluorescent lights from first phase of two-phase culture. The highest lipid production of P. atomus was 50.3% (w/w) with green LED light at 2 days of second phase as light stress. Fatty acid analysis of the microalgae showed that palmitic acid (C16:0) and linolenic acid (C18:3) accounted for 84–88% (w/w) of total fatty acids from P. atomus . The two-phase culture of P. atomus is suitable for biofuel production due to higher lipid productivity and favorable fatty acid composition. [ABSTRACT FROM AUTHOR]

Conditions of light-emitting diode (LED) wavelength, light intensity, nitrate concentration, and time of exposure to green LED light stress in a two-phase culture were optimized for lipid production with three species of microalgae. Among the three microalgae, Nannochloropsis oculata showed the highest specific growth rate ( μ max ) of 0.037 h −1 and the lowest saturation constant ( K s ) of 1.32 mg/L. The highest lipid contents of the three microalgae in the second phase under green LED light stress were 52.0% (w/w) for Nannochloropsis salina at 2 days, 53.0% (w/w) for Nannochloropsis oceanica at 2 days, and 56.0% for N. oculata at 2 days. Fatty acid analysis of the microalgae showed that 85–87% (w/w) of total fatty acids from N. salina , N. oceanica , and N. oculata consisted of palmitic acid (C16:0) and oleic acid (C18:1). [ABSTRACT FROM AUTHOR]

• Horse manure (HM) was employed as a feedstock for bioethanol production. • High holocellulose contents in HM produced fermentable sugars with 80% yield. • N-rich HM showed competitive ethanol production (0.075 g L-1h−1) with no N support. Insecure supply chain of biomass has been regarded as one of the critical constraints for deteriorating the practical implementations of bioethanol (BE). To find a raw feedstock beyond lignocellulosic biomass, horse manure (HM) was converted into BE. To realize the grand premise, two pretreatment methods, acid-/alkaline-pretreatments using H 2 SO 4 /NaOH, were used for HM. To optimize acid-/alkaline-pretreatments, the surface methodology response with the Box-Behnken design was done. Under the optimized conditions, alkaline-pretreatment showed higher maximum sugar recovery yield (80%) than that from acid- pretreatment (71%), which offers that alkaline-pretreatment is suitable for BE synthesis from HM. The fermentability of acid/enzyme- and alkaline/enzyme-hydrolysates without a supplement of nitrogen source were tested using GRAS strain of yeast, Pichia stipitis. The results indicated that alkaline/enzyme- hydrolysates showed higher BE productivities (0.075 g L-1h−1) than those of acid/enzyme-hydrolysates (0.050 g L-1h−1). To elucidate the possible reasons of such higher BE productivities from the alkaline/enzyme- hydrolysates, the potential fermentative inhibitory compounds for Pichia stipitis such as acetic acid, furfural, and hydroxymethylfurfural were quantitatively analyzed. The results indicated that the presence of less amounts of toxic compounds from the alkaline/enzyme- hydrolysates may lead to such higher BE productivities as compared those present in acid/enzyme-hydrolysates. Also, all experimental results suggested a potential for saving production cost of BE using HM as the C/N sources without an additional nitrogen source supplement. [ABSTRACT FROM AUTHOR]

• I. galbana was cultured in 14-L photobioreactors using two-phase culture system. • Maximum biomass and lipid content was obtained with 18:6 h and 400 µmol/m2/s. • Maximum biomass and lipid content was 1.25 g dcw/L and 71.1% (w/w), respectively. • SFAs decreased as light intensity increases while and vice versa for UFAs. • Stearic acid (C18) was the most dominant fatty acid. The optimal light intensity and photoperiod required to produce high biomass and lipid contents in Isochrysis galbana cultured in a 14-L bioreactor with LED wavelengths was studied. The cell biomass production was monitored in the first phase comprising of mixed blue (465 nm) and red (640 nm) LED wavelengths, then green (520 nm) LED were used in the second phase for lipid production. The optimal light intensity was 400 µmol/m2/s giving a maximum cell biomass of 1.05 g dcw/L and total lipid content of 65.2% (w/w) cultured under 12:12 h L/D cycle. The optimal light intensity of 400 µmol/m2/s was applied at different L/D cycles, the maximum cell biomass (1.25 g dcw/L) and lipid content (71.1% w/w) were obtained at 18:6 h L/D cycle. Stearic acid was the main fatty acid ranging from 42.91 (500 µmol/m2/s) to 65.57% w/w (100 µmol/m2/s) and 53.84 (18:6 h) to 65.44% w/w (24:0 h). [ABSTRACT FROM AUTHOR]