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Applying a circular economy approach, this research explores the use of cheese whey permeate (CWP), by-product of whey ultrafiltration, as cheap substrate for the production of bacterial cellulose (BC) and Sakacin-A, to be used in an antimicrobial packaging material. BC from the acetic acid bacterium Komagataeibacter xylinus was boosted up to 6.77 g/L by supplementing CWP with β-galactosidase. BC was then reduced to nanocrystals (BCNCs, 70% conversion yield), which were then conjugated with Sakacin-A, an anti-Listeria bacteriocin produced by Lactobacillus sakei in a CWP based broth. Active conjugates (75 Activity Units (AU)/mg), an innovative solution for bacteriocin delivery, were then included in a coating mixture applied onto paper sheets at 25 AU/cm2. The obtained antimicrobial food package was found effective in reducing Listeria population in storage trials carried out on a fresh Italian soft cheese (named "stracchino") intentionally inoculated with Listeria. Production costs of the active material have been mainly found to be associated (90%) to the purification steps. Setting a maximum prudential 50% cost reduction during process up-scaling, conjugates coating formulation would cost around 0.89 €/A4 sheet. Results represent a practical example of a circular economy production procedure by using a food industry by-product to produce antimicrobials for food preservation. [ABSTRACT FROM AUTHOR]

Traditional autoclaving, slow degradation rate and preservation of biomass treated by fungi are the main factors restricting biological treatment. In our previous studies, strains with high efficiency and selective lignin degradation ability were obtained. To further solve the limiting factors of biological treatment, this paper proposed a composite treatment technology, which could replace autoclaves for fungal treatment and improve the preservation and utilization of fungal-pretreated straw. The autoclaved and expanded buckwheat straw were, respectively, degraded by Irpex lacteus for 14 days (CIL, EIL), followed by ensiling of raw materials (CK) and biodegraded straw of CIL and EIL samples with Lactobacillus plantarum for different days, respectively (CP, CIP, EIP). An expansion led to lactic acid bacteria, mold, and yeast of the samples below the detection line, and aerobic bacteria was significantly reduced, indicating a positive sterilization effect. Expansion before I. lacteus significantly enhanced lignin selective degradation by about 6%, and the absolute content of natural detergent solute was about 5% higher than that of the CIL. Moreover, EIL decreased pH by producing higher organic acids. The combination treatment created favorable conditions for ensiling. During ensiling, EIP silage produced high lactic acid about 26.83 g/kg DM and the highest acetic acid about 22.35 g/kg DM, and the pH value could be stable at 4.50. Expansion before I. lacteus optimized the microbial community for ensiling, resulting in EIP silage co-dominated by Lactobacillus, Pediococcus and Weissella, whereas only Lactobacillus was always dominant in CP and CIP silage. Clavispora gradually replaced Irpex in EIP silage, which potentially promoted lactic acid bacteria growth and acetic acid production. In vitro gas production (IVGP) in EIL was increased by 30% relative to CK and was higher than 24% in CIL. The role of expansion was more significant after ensiling, the IVGP in EIP was increased by 22% relative to CP, while that in CIP silage was only increased by 9%. Silage of fungal-treated samples reduced methane emissions by 28% to 31%. The study demonstrated that expansion provides advantages for fungal colonization and delignification, and further improves the microbial community and fermentation quality for silage, enhancing the nutrition and utilization value. This has practical application value for scaling up biological treatment and preserving the fungal-treated lignocellulose. [ABSTRACT FROM AUTHOR]

Gluconobacter oxydans is a well-known acetic acid bacterium that has long been applied in the biotechnological industry. Its extraordinary capacity to oxidize a variety of sugars, polyols, and alcohols into acids, aldehydes, and ketones is advantageous for the production of valuable compounds. Relevant G. oxydans industrial applications are in the manufacture of L-ascorbic acid (vitamin C), miglitol, gluconic acid and its derivatives, and dihydroxyacetone. Increasing efforts on improving these processes have been made in the last few years, especially by applying metabolic engineering. Thereby, a series of genes have been targeted to construct powerful recombinant strains to be used in optimized fermentation. Furthermore, low-cost feedstocks, mostly agro-industrial wastes or byproducts, have been investigated, to reduce processing costs and improve the sustainability of G. oxydans bioprocess. Nonetheless, further research is required mainly to make these raw materials feasible at the industrial scale. The current shortage of suitable genetic tools for metabolic engineering modifications in G. oxydans is another challenge to be overcome. This paper aims to give an overview of the most relevant industrial G. oxydans processes and the current strategies developed for their improvement. [ABSTRACT FROM AUTHOR]

Microbial production ofd-hexosaminate was examined by means of oxidative fermentation with acetic acid bacteria. In most strains of acetic acid bacteria, membrane-boundd-glucosamine dehydrogenase (synonymous with an alternatived-glucose dehydrogenase distinct from quinoproteind-glucose dehydrogenase) oxidizedd-hexosamines to the correspondingd-hexosaminates in a stoichiometric manner. Conversion ofd-hexosamines to the correspondingd-hexosaminates was observed with growing cells of acetic acid bacteria, andd-hexosaminate was stably accumulated in the culture medium even thoughd-hexosamine was exhausted. Since the enzyme responsible is located on the outer surface of the cytoplasmic membrane, and the enzyme activity is linked to the respiratory chain of the organisms, resting cells, dried cells, and immobilized cells of acetic acid bacteria were effective catalysts ford-hexosaminate production.d-Mannosaminate andd-galactosaminate were also prepared for the first time by means of oxidative fermentation, and three differentd-hexosaminates were isolated from unreacted substrate by a chromatographic separation. In this paper,d-hexosaminate production by oxidative fermentation carried out mainly withGluconobacter frateuriiIFO 3264 is exemplified as a typical example. [ABSTRACT FROM AUTHOR]

Gaining a comprehensive understanding of the role played by the oral microbiome in moderate to severe plaque psoriasis and its potential implications for disease management and development holds significant importance. With the objective of exploring correlations between the oral microbiota and severe psoriasis, this study involved 72 severe psoriasis patients and 16 healthy individuals, whose clinical manifestations and living habits were carefully recorded. Cutting-edge techniques such as 16S rRNA gene sequencing and bioinformatics analysis were employed to compare the microbial flora, investigating dynamic changes among severe plaque psoriasis patients, psoriatic arthritis patients and healthy individuals. The findings revealed noteworthy patterns including increased levels of Aggregatibacter in the psoriatic arthritis group, accompanied by a decrease in the level of Prevotella. Moreover, the enrichment o Capnocytandophaga (P = 0.009), Campylobacter (P = 0.0022), and Acetobacter (P = 0.0292) was notably more substantial in the psoriasis group compared to the control group, whereas certain bacterial species such as Bacteroides (P = 0.0049), Muribaculaceae (P = 0.0048) demonstrated decreased enrichment. Additionally, the psoriatic arthritis group exhibited significantly higher levels of Ralstonia, Bifidobacterium and Micromonospora. Based on these findings, it can be inferred that individuals with lower levels of Prevotella and higher levels of Corynebacterium may be more susceptible to psoriasis exacerbation. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) represents a renewable biomaterial with unique properties promising for biotechnology and biomedicine. Komagataeibacter hansenii ATCC 53,582 is a well-characterized high-yield producer of BC used in the industry. Its genome encodes three distinct cellulose synthases (CS), bcsAB1, bcsAB2, and bcsAB3, which together with genes for accessory proteins are organized in operons of different complexity. The genetic foundation of its high cellulose-producing phenotype was investigated by constructing chromosomal in-frame deletions of the CSs and of two predicted regulatory diguanylate cyclases (DGC), dgcA and dgcB. Proteomic characterization suggested that BcsAB1 was the decisive CS because of its high expression and its exclusive contribution to the formation of microcrystalline cellulose. BcsAB2 showed a lower expression level but contributes significantly to the tensile strength of BC and alters fiber diameter significantly as judged by scanning electron microscopy. Nevertheless, no distinct extracellular polymeric substance (EPS) from this operon was identified after static cultivation. Although transcription of bcsAB3 was observed, expression of the protein was below the detection limit of proteome analysis. Alike BcsAB2, deletion of BcsAB3 resulted in a visible reduction of the cellulose fiber diameter. The high abundance of BcsD and the accessory proteins CmcAx, CcpAx, and BglxA emphasizes their importance for the proper formation of the cellulosic network. Characterization of deletion mutants lacking the DGC genes dgcA and dgcB suggests a new regulatory mechanism of cellulose synthesis and cell motility in K. hansenii ATCC 53,582. Our findings form the basis for rational tailoring of the characteristics of BC. Key points: • BcsAB1 induces formation of microcrystalline cellulose fibers. • Modifications by BcsAB2 and BcsAB3 alter diameter of cellulose fibers. • Complex regulatory network of DGCs on cellulose pellicle formation and motility. [ABSTRACT FROM AUTHOR]

The gut is continuously invaded by diverse bacteria from the diet and the environment, yet microbiome composition is relatively stable over time for host species ranging from mammals to insects, suggesting host-specific factors may selectively maintain key species of bacteria. To investigate host specificity, we used gnotobiotic Drosophila, microbial pulse-chase protocols, and microscopy to investigate the stability of different strains of bacteria in the fly gut. We show that a host-constructed physical niche in the foregut selectively binds bacteria with strain-level specificity, stabilizing their colonization. Primary colonizers saturate the niche and exclude secondary colonizers of the same strain, but initial colonization by Lactobacillus species physically remodels the niche through production of a glycan-rich secretion to favor secondary colonization by unrelated commensals in the Acetobacter genus. Our results provide a mechanistic framework for understanding the establishment and stability of a multi-species intestinal microbiome. Animal gut microbiomes are fairly stable over time despite large daily fluctuations in diet and introductions of environmental bacteria. Here the authors report that fruit flies maintain the stability of their microbiome in part through a physical niche in the esophagus. [ABSTRACT FROM AUTHOR]

Improper fermentation of pineapple wine owing to volatile acidity has been associated with excessive proliferation of acetic acid bacteria during fermentation and consequent increased acetic acid concentration. Mid-infrared (MIR) and near-infrared (NIR) spectroscopies were employed to classify improper pineapple wine fermentation. Two clusters of samples possessing within the limit and over-limit acetic acid content were obtained using low-grade pineapples and prepared accordingly. Spectral data were collected for all samples in the 4000–650 cm−1 region using attenuated total reflection (ATR) with an FT-MIR spectrophotometer and in the 11,536–5800 cm−1 using sample vials and 11,536–3952 cm−1 regions using a liquid probe and a liquid cup with an FT-NIR spectrophotometer. The classification models for pineapple wine fermentation based on acetic acid content were constructed using soft independent modeling of class analogy (SIMCA) and partial least squares discriminant analysis (PLSDA). Comparisons of MIR and NIR techniques, classification methods, and spectral pretreatments have been reported. The results demonstrated that MIR spectroscopy coupled with ATR and PLSDA is highly effective for the detection of improper pineapple wine fermentation as a function of acetic acid content. The best classification model was generated using the entire MIR spectra after second derivatives transformation, which provided the highest accuracy, sensitivity, specificity, and precision. [ABSTRACT FROM AUTHOR]

Room-temperature sodium-based batteries have the potential for meeting large-scale grid energy storage needs. Inspired by the advancement of the design and building of electrode materials in lithium ion batteries, improved nano-architectured electrodes can be created for sodium-ion batteries, allowing increased electron transport kinetics and conductivities. Here, nanocomposites with 3D porous structures are reported as a high-capacity anode material for sodium-ion batteries by using an easy, low-cost and environmentally friendly synthesis of pyrolyzed bacterial celluloses (PBCs). Bacterial celluloses (BCs) produced by the Gluconacetobacter xylinus strain are pyrolyzed at 500, 750 and 1000 °C, resulting 50, 130 and 110 mAh g capacities over 80 numbers of cycles, respectively, in the presence of the binary ethylene carbonate-propylene carbonate mixture. In order to increase the cell performances, in situ coated SnO nanoparticles with bacterial cellulose (SnO@PBC) are produced by addition as synthesized 5-nm-sized SnO nanoparticles into the BC growth medium together with the G. xylinus strain. Following the pyrolysis at 500 °C, the SnO@PBC composite is better able to handle the accommodation of the dramatic volume change of the incorporated SnO nanoparticles because of the interaction of oxygen-containing moieties of bacterial cellulose nanofibrils with the SnO nanoparticles during cellulose production. The resulting SnO@PBC composite presents highly stable capacity retention of around 400 mAh g capacities at C/10 current density over 50 numbers of cycles. [ABSTRACT FROM AUTHOR]

Bacterial Cellulose (BC) production is still considered expensive and challenging for industries. Herein, BC was produced through an acetic acid bacteria isolated from the kombucha consortium and an extract from acerola juice-industrial waste. The isolated bacterium was characterized through different assays (biochemical characterization and 16S rRNA gene) being identified as Komagataeibacter rhaeticus. BC production with static cultivation mode by the isolated strain was compared using traditional Hestrin-Schramm (HS) medium and acerola waste (AC) (5% w/v). The kinetic behavior of BC production was slightly higher in the HS medium reaching 2.9 g/L after 12 days of fermentation, while 2.3 g/L in the AC medium. Minor differences were observed between crystallinity, crystallite size, and d-spacing, highlighting BC produced by the AC medium two-fold breaking stress resistance compared to the conventional medium, with high-temperature stability and economically feasible, promissory results for further application of this synthesized cellulose obtained from industrial residues. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) produced by the Komagateibacter sucrofermentas VKPM B-11267 bacteria was used as a carrier for immobilization of acetic acid bacteria Gluconobacter oxydans in amperometric biosensors. The bioreceptor was formed on the surface of a screen-printed graphite electrode modified with thermally expanded graphite (TEG) or on the surface of a porous three-dimensional material, nickel foam (NF). Structural features of these materials contributed to the creation of a firm contact between the electrode material and the surface of the BC on which the bacterial cells were immobilized. Scanning electron microscopy showed that bacteria not only sorb on the surface of BC but are also able to penetrate the inner volume of the film. Conductivity of both types of biosensors was studied using impedance spectroscopy and the resistance of the graphite electrode was shown to decrease by three orders of magnitude after its surface is modified with TEG. Bioelectrodes containing BC were used in the construction of an amperometric biosensor for glucose determination. The sensitivity of the biosensor was 3 μA/mM × cm2. Thus, BC in combination with TEG and NF can be used to create three-dimensional electrodes of bioelectrocatalytical devices. [ABSTRACT FROM AUTHOR]

Cellulose is produced by all plants and a number of other organisms, including bacteria. The most representative cellulose-producing bacterial species is Gluconacetobacter xylinus, an acetic acid bacterium. Cellulose produced by G. xylinus, commonly referred to as bacterial cellulose (BC), has exceptional physicochemical properties resulting in its use in a variety of applications. All cellulose-producing organisms that synthesize cellulose microfibrils have membrane-localized protein complexes (also called terminal complexes or TCs) that contain the enzyme cellulose synthase and other proteins. The bacterium G. xylinus is a prolific cellulose producer and a model organism for studies on cellulose biosynthesis. The widths of cellulose fibers produced by Gluconacetobacter are 50–100 nm, suggesting that cellulose-synthesizing complexes are nanomachines spinning a nanofiber. At least four different proteins (BcsA, BcsB, BcsC, and BcsD) are included in TC from Gluconacetobacter, and the proposed function of each is as follows: BcsA, synthesis of a glucan chain through glycosyl transfer from UDP-glucose; BcsB, complexes with BcsA for cellulose synthase activity; BcsC, formation of a pore in the outer membrane through which a glucan chain is extruded; BcsD, regulates aggregation of glucan chains through four tunnel-like structures. In this review, we discuss structures and functions of these four and a few other proteins that have a role in cellulose biosynthesis in bacteria. [ABSTRACT FROM AUTHOR]

The work considered the properties of a biosensor based on a novel nanomaterial—modified thermally expanded graphite (TEGM). The main focus was on whether the procedure of additional graphite thermal expansion would affect the electrochemical properties of biosensors based on membrane fractions of acetic acid bacteria Gluconobacter oxydans. Raman spectroscopy, scanning electron microscopy and electrochemical analysis were used for the study. Raman spectra showed that the formation of TEGM led to its stratification into smaller particles and a better orderly layered structure with high "graphenization" degree. Modification of TEG led to the formation of additional cavities into which bacterial cells or bacterial membrane fractions could be immobilized and affect the electrical conductivity of the biosensors positively. Calculation of the heterogeneous charge transfer constants showed that processes occurring on the electrodes are quasi-reversible. The limiting stage of these processes is the transfer of an electron from a biological component on the electrode surface, not the diffusion of the analyte from the solution to the active centers of the enzyme. We showed the possibility of developing third-generation mediator-free biosensors for glucose detection based on TEGM, as well as of second-generation mediator biosensors for glucose, ethanol and glycerol detection. [ABSTRACT FROM AUTHOR]

Acetic acid bacteria (AAB) are industrial microorganisms used for vinegar fermentation. Herein, we investigated the distribution and genome structures of mitomycin C-inducible temperate phages in AAB. Transmission electron microscopy analysis revealed phage-like particles in 15 out of a total 177 acetic acid bacterial strains, all of which showed morphology similar to myoviridae-type phage. The complete genome sequences of the six phages derived from three strains each of Acetobacter and Komagataeibacter strains were determined, harboring a genome size ranging from 34,100 to 53,798 bp. A phage AP1 from A. pasteurianus NBRC 109446 was predicted as an active phage based on the genomic information, and actually had the ability to infect its phiAP1-cured strain. The attachment sites for phiAP1 were located in the 3'-end region of the tRNAser gene. We also developed a chromosome-integrative vector, p2096int, based on the integrase function of phiAP1, and it was successfully integrated into the attachment site of the phiAP1-cured strain, which may be used as a valuable tool for the genetic engineering. Overall, this study showed the distribution of mitomycin C-inducible temperate phages in AAB, and identified the active temperate phage o f A. pasteurianus. [ABSTRACT FROM AUTHOR]

Acetic acid bacteria (AAB) can selectively oxidize diols into their corresponding hydroxyacids. Notably, they can convert 1,3-propanediol (1,3-PDO) into 3-hydroxypropionic acid (3-HP), which is a promising building-block. Until now, 3-HP production with AAB is carried out in batch and using resting cells at high cell densities (up to 10 g L−1 of cell dry weight). This approach is likely limited by detrimental accumulation of the intermediate 3-hydroxypropanal (3-HPA). Herein, we investigate an alternative implementation that allows highly efficient 3-HP production with lower cell densities of growing cells and that prevents 3-HPA accumulation. First, growth and 3-HP production of Acetobacter sp. CIP 58.66 were characterized with 1,3-PDO or glycerol as growth substrate. The strain was then implemented in a bioreactor, during a sequential process where it was first cultivated on glycerol, then the precursor 1,3-PDO was continuously supplied at a varying rate, easily controlled by the pH control. Different pH set points were tested (5.0, 4.5, and 4.0). This approach used the natural resistance of acetic acid bacteria to acidic conditions. Surprisingly, when pH was controlled at 5.0, the performances achieved in terms of titer (69.76 g3-HP L−1), mean productivity (2.80 g3-HP L−1 h−1), and molar yield (1.02 mol3-HP mol−11,3-PDO) were comparable to results obtained with genetically improved strains at neutral pH. The present results were obtained with comparatively lower cell densities (from 0.88 to 2.08 g L−1) than previously reported. This feeding strategy could be well-suited for future scale-up, since lower cell densities imply lower process costs and energy needs. [ABSTRACT FROM AUTHOR]

Antifungal and antibacterial activities of twenty-six combinations of lactic acid bacteria, propionibacteria, acetic acid bacteria and dairy yeasts inoculated in whey and milk were investigated. Associations including acetic acid bacteria were shown to suppress growth of the opportunistic yeast Candida albicans in well-diffusion assays. The protective effect of milk fermented with the two most promising consortia was confirmed in Caco-2 cell culture infected with C. albicans. Indeed, these fermented milks, after heat-treatment or not, suppressed lactate dehydrogenase release after 48 h while significant increase in LDH release was observed in the positive control (C. albicans alone) and with fermented milk obtained using commercial yogurt starter cultures. The analysis of volatile compounds in the cell-free supernatant using solid phase microextraction (SPME) coupled to gas chromatography–mass spectrometry (GC–MS) showed accumulation of significant amount of acetic acid by the consortium composed of Lactobacillus delbrueckii 5, Lactobacillus gallinarum 1, Lentilactobacillus parabuchneri 3, Lacticaseibacillus paracasei 33-4, Acetobacter syzygii 2 and Kluyveromyces marxianus 19, which corresponded to the zone of partial inhibition of C. albicans growth during well-diffusion assays. Interestingly, another part of anti-Candida activity, yielding small and transparent inhibition zones, was linked with the consortium cell fraction. This study showed a correlation between anti-Candida activity and the presence of acetic acid bacteria in dairy associations as well as a significant effect of two dairy associations against C. albicans in a Caco-2 cell model. These two associations may be promising consortia for developing functional dairy products with antagonistic action against candidiasis agents. [ABSTRACT FROM AUTHOR]

Acetic acid bacteria (AAB) are a group of Gram-negative and strictly aerobic microorganisms widely used in vinegar industry, especially the species belonging to the genera Acetobacter and Komagataeibacter. The environments inhabited by AAB during the vinegar fermentation, in particular those natural traditional bioprocesses, are complex and dynamically changed, usually accompanied by diverse microorganisms, bacteriophages, and the increasing acetic acid concentration. For this reason, how AAB survive to such harsh niches has always been an interesting research field. Previous omic analyses (e.g., genomics, proteomics, and transcriptomics) have provided abundant clues for the metabolic pathways and bioprocesses indispensable for the acid stress adaptation of AAB. Nevertheless, it is far from fully understanding what factors regulate these modular mechanisms overtly and covertly upon shifting environments. Bacterial toxin-antitoxin systems (TAS), usually consisting of a pair of genes encoding a stable toxin and an unstable antitoxin that is capable of counteracting the toxin, have been uncovered to have a variety of biological functions. Recent studies focusing on the role of TAS in Acetobacter pasteurianus suggest that TAS contribute substantially to the acid stress resistance. In this mini review, we discuss the biological functions of type II TAS in the context of AAB with regard to the acid stress resistance, persister formation and resuscitation, genome stability, and phage immunity. Key points: • Type II TAS act as regulators in the acid stress resistance of AAB. • Type II TAS are implicated in the formation of acid-tolerant persister cells in AAB. • Type II TAS are potential factors responsible for phage immunity and genome stability. [ABSTRACT FROM AUTHOR]

Elucidation of the acetic acid resistance (AAR) mechanisms is of great significance to the development of industrial microbial species, specifically to the acetic acid bacteria (AAB) in vinegar industry. Currently, the role of population heterogeneity in the AAR of AAB is still unclear. In this study, we investigated the persister formation in AAB and the physiological role of HicAB in Acetobacter pasteurianus Ab3. We found that AAB were able to produce a high level of persister cells (10−2 to 100 in frequency) in the exponential-phase cultures. Initial addition of acetic acid and ethanol reduced the ratio of persister cells in A. pasteurianus by promoting the intracellular ATP level. Further, we demonstrated that HicAB was an important regulator of AAR in A. pasteurianus Ab3. Strains lacking hicAB showed a decreased survival under acetic acid exposure. Deletion of hicAB significantly diminished the acetic acid production, acetification rate, and persister formation in A. pasteurianus Ab3, underscoring the correlation between hicAB, persister formation, and acid stress resistance. By transcriptomic analysis (RNA-seq), we revealed that HicAB contributed to the survival of A. pasteurianus Ab3 under high acid stress by upregulating the expression of genes involved in the acetic acid over-oxidation and transport, 2-methylcitrate cycle, and oxidative phosphorylation. Collectively, the results of this study refresh our current understanding of the AAR mechanisms in A. pasteurianus, which may facilitate the development of novel ways for improving its industrial performance and direct the scaled-up vinegar production. Key points: • AAB strains form persister cells with different frequencies. • A. pasteurianus are able to form acid-tolerant persister cells. • HicAB contributes to the AAR and persister formation in A. pasteurianus Ab3. [ABSTRACT FROM AUTHOR]

Acetic acid accumulation is a universal limiting factor to the vinegar manufacture because of the toxic effect of acetic acid on the acid producing strain, such as Acetobacter pasteurianus. In this study, we aimed to investigate the genome-wide transcriptional response of A. pasteurianus Ab3 to high acid stress during vinegar production. By comparing the transcriptional landscape of cells harvested from a long-term cultivation with high acidity (70 ± 3 g/L) to that of low acidity (10 ± 2 g/L), we demonstrated that 1005 genes were differentially expressed. By functional enrichment analysis, we found that the expression of genes related to the two-component systems (TCS) and toxin-antitoxin systems (TAS) was significantly regulated under high acid stress. Cells increased the genome stability to withstand the intracellular toxicity caused by the acetic acid accumulation by repressing the expression of transposases and integrases. Moreover, high acid stress induced the expression of genes involved in the pathways of peptidoglycan, ceramide, and phosphatidylcholine biosynthesis as well as the Tol-Pal and TonB-ExbB systems. In addition, we observed that cells increased and diversified the ATP production to resist high acid stress. Transcriptional upregulation in the pathways of pyrroloquinoline quinone (PQQ) synthesis and thiamine metabolism suggested that cells may increase the production of prosthetic groups to ensure the enzyme activity upon high acid stress. Collectively, the results of this study increase our current understanding of the acetic acid resistance (AAR) mechanisms in A. pasteurianus and provide opportunities for strain improvement and scaled-up vinegar production. Key Points • TCS and TAS are responsive to the acid stress and constitute the regulating networks. • Adaptive expression changes of cell envelope elements help cell resist acid stress. • Cells promote genome stability and diversify ATP production to withstand acid stress. [ABSTRACT FROM AUTHOR]

Bacterial cellulose has unique structural, functional, physical and chemical properties. The mass production of bacterial cellulose for industrial application has recently become more popular and attractive. The aim of this study was to develop an efficient scale-up process of bacterial cellulose production. Bacterial cellulose productivity of a new isolate Acetobacter pasteurianus RSV-4 (MTCC 25117) was investigated in whey medium without addition of any additives. Produced bacterial cellulose was characterized for its structure, purity, thermostability and strength by Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis and Differential scanning calorimetry. β-galactosidase (1.5 IU/ml) was used to split whey lactose into its corresponding monomers glucose and galactose. Glucose was specifically consumed by Acetobacter pasteurianus for the production of BC. The highest concentration of 5.6 g cellulose/L of whey was obtained at 30 °C after 8 days of bacterial growth. Process was optimized for the production of bacterial cellulose on 120 L of whey medium under static conditions. Whey, a waste byproduct of milk processing industry was used in the process and therefore the developed process might be economical. [ABSTRACT FROM AUTHOR]

Elucidation of the acetic acid resistance (AAR) mechanisms of Acetobacter pasteurianus is significant for vinegar production. In this study, cell membrane lipid profile of A. pasteurianus Ab3 was investigated by gas chromatography-mass spectrometer (GC–MS) and high performance liquid chromatography–electrospray ionization (HPLC-ESI) combined with high resolution accurate mass/mass spectrometry (HRAM/MS). We observed that cell remodeled the membrane physical state by decreasing the ratio of saturated fatty acids (SFAs)/unsaturated fatty acids (UFAs), and increasing the chain length of fatty acids (FAs) and the content of cyclopropane FAs in response to extreme acid stress. Noticeably, the content of octadecadienoic acid (C18:2) elevated remarkably. Moreover, a continuous reduction in cell membrane fluidity and a "V-type" variance in permeability were discovered. The content of glycerophospholipid and ceramide increased significantly in cells harvested from culture with acidity of 75 g/L and 95 g/L compared to that with acidity of 30 g/L. Among the identified lipid species, the content of phosphatidylcholine (e.g. PC 19:0/18:2 and 19:1/18:0), ceramide (e.g. Cer d18:0/16:1 and d18:0/16:1 + O), and dimethylphosphatidylethanolamine (e.g. dMePE 19:1/16:1) increased notably with increasing acidity. Collectively, these findings refresh our current understanding of the AAR mechanisms in A. pasteurianus Ab3, and should direct future strain breeding and vinegar fermentation. [ABSTRACT FROM AUTHOR]

The main goal was to evaluate if dried cyanobacterium (Arthrospira platensis) biomass added to unpasteurised apple juice could inhibit growth of fungi dominant in apples and which fraction of cyanobacterium biomass contributed to this phenomenon. A. platensis biomass, its protein and/or polysaccharide fraction were added to the sterilised apple juice inoculated with Aureobasidium pullulans LW14 and stored at 4 °C for 96 h. Samples were tested against number of fungi and selected physical–chemical parameters. In the last research stage, protein fraction was added to the unpasteurised apple juice inoculated with A. pullulans LW14 to test its potency against fungi, lactic acid bacteria and acetic acid bacteria. When A. platensis biomass was added to the sterilised apple juice (1.15% w/v), it effectively inhibited growth of A. pullulans LW14 and the metabolism of all analysed sugars (glucose, sucrose and fructose). Protein fraction added to the sterilised apple juice contributed significantly to mycostatic properties of A. platensis. When protein fraction was added to unpasteurised apple juice, the same conclusions were obtained, however, except for inhibiting growth of A. platensis LW14, it inhibited growth of some bacteria. [ABSTRACT FROM AUTHOR]

It is imperative that promising bacterial cellulose-producing bacteria mainly belongs to genera Acetobacter (acid-producing bacteria). In order to screen cellulose-producing Acetobacter, the isolated cultures from vinegar/rotten fruits were inoculated in Hestrin-Schramm (HS) medium containing ethanol and CaCO3. After the desired incubation, the positive cultures form a zone, which is observed around the bacterial growth, resulted from the solubilization of CaCO3 by acetic acid produced from the oxidation of ethanol during fermentation. However, in this method, the clarity of the solubilized zone is not very sharp and distinct. In the present, investigation, an improved method for screening, of the microorganisms producing acetic acid has been developed. In this method, methyl red (MR) is incorporated as a pH indicator in HS medium containing ethanol and CaCO3. Plates containing MR at alkaline pH are yellow and turn dark red at acidic pH. Thus, a distinctive, clear zone is formed around bacterial colonies producing acetic acid and is easy to differentiate between acid producers and non-producers. The present method is more rapid, accurate, and sensitive and can be successfully be used for the detection of acetic acid-producing bacteria particularly for the screening of potent cellulose producer Acetobacter sp. [ABSTRACT FROM AUTHOR]

Environmental stresses experienced during development exert many long-term effects upon health and disease. For example, chemical oxidants or genetic perturbations that induce low levels of reactive oxygen species can extend lifespan in several species. In some cases, the beneficial effects of low-dose oxidants are attributed to adaptive protective mechanisms such as mitohormesis, which involve long-term increases in the expression of stress response genes. Here we show in Drosophila that transient exposure to low concentrations of oxidants during development leads to an extension of adult lifespan. Surprisingly, this depends upon oxidants acting in an antibiotic-like manner to selectively deplete the microbiome of Acetobacter proteobacteria. We demonstrate that the presence of Acetobacter species, such as A. aceti, in the indigenous microbiota increases age-related gut dysfunction and shortens lifespan. This study demonstrates that low-dose oxidant exposure during early life can extend lifespan via microbiome remodelling rather than mitohormesis. [ABSTRACT FROM AUTHOR]

Cellulose is a major biopolymer on the earth that is produced by cellulose synthase in the cell membrane of living organisms. Cellulose synthase is a hetero-subunit complex composed of several different protein subunits, and is visualized as a supermolecular complex called a 'terminal complex' by electron microscopy. Such supermolecular organization of an enzyme complex is believed to be important for the fiber formation or crystallization of cellulose microfibrils in cellulose biosynthesis. In the case of the cellulose-producing bacterium Acetobacter, it is hypothesized that the enzyme complex includes at least six subunits given its genetic constitution. However, to date, only three of these molecules have been experimentally confirmed as the subunits included in the terminal complex: CesB, CesD, and ccp2. In this study, we used fluorescence immuno-microscopy to show that CesA protein, the catalytic subunit, is included in the terminal complex of Acetobacter. Furthermore we discuss the obtained microscopic data for improving our understanding of the molecular organization of the bacterial cellulose synthase complex. [ABSTRACT FROM AUTHOR]

Bacterial cellulose (BC) is a homopolymer and it is distinguished from plant-based cellulose by its unique properties such as high purity, high crystallinity, high water-holding capacity, and good biocompatibility. Microalgae are unicellular, photosynthetic microorganisms and are known to have high protein, starch, and oil content. In this study, Chlorella vulgaris was evaluated as source of glucose for the production of BC. To increase the starch content of algae the effect of nutrient starvation (nitrogen and sulfur) and light deficiency were tested in a batch assay. The starch contents (%) were 5.27 ± 0.04, 7.14 ± 0.18, 5.00 ± 0.08, and 1.35 ± 0.04 for normal cultivation, nitrogen starvation, sulfur starvation, and dark cultivation conditions, respectively. The performance of enzymatic and acidic methods was compared for the starch hydrolysis. This study demonstrated for the first time that acid hydrolysate of algal starch can be used to substitute glucose in the fermentation medium of Komagataeibacter hansenii for BC production. Glucose was used as a control for BC production. BC production yields on dry weight basis were 1.104 ± 0.002 g/L and 1.202 ± 0.005 g/L from algae-based glucose and glucose, respectively. The characterization of both BCs produced from glucose and algae-based glucose was investigated by scanning electron microscopy and Fourier transform infrared spectroscopy. The results have shown that the structural characteristics of algae-based BC were comparable to those of glucose-based BC. [ABSTRACT FROM AUTHOR]

We report the ability of cellulose to support cells without the use of matrix ligands on the surface of the material, thus creating a two-component system for tissue engineering of cells and materials. Sheets of bacterial cellulose, grown from a culture medium containing Acetobacter organism were chemically modified with glycidyltrimethylammonium chloride or by oxidation with sodium hypochlorite in the presence of sodium bromide and 2,2,6,6-tetramethylpipiridine 1-oxyl radical to introduce a positive, or negative, charge, respectively. This modification process did not degrade the mechanical properties of the bulk material, but grafting of a positively charged moiety to the cellulose surface (cationic cellulose) increased cell attachment by 70% compared to unmodified cellulose, while negatively charged, oxidised cellulose films (anionic cellulose), showed low levels of cell attachment comparable to those seen for unmodified cellulose. Only a minimal level of cationic surface derivitisation (ca 3% degree of substitution) was required for increased cell attachment and no mediating proteins were required. Cell adhesion studies exhibited the same trends as the attachment studies, while the mean cell area and aspect ratio was highest on the cationic surfaces. Overall, we demonstrated the utility of positively charged bacterial cellulose in tissue engineering in the absence of proteins for cell attachment. [ABSTRACT FROM AUTHOR]

3-hydroxypropionic acid (3-HP) is an important chemical platform organic in material industry, daily chemical industry and biomedicine field due to its numerous valuable derivatives. However, no mature methods have been established in the synthesis industry for direct large scale production. The bacterium Acetobacter sp. CGMCC 8142 with high efficiency of alcohols oxidation property was immobilized for biosynthesis of 3-HP from 1, 3-propanediol (1, 3-PDO). Parameter values in mass transfer modeling indicated that mass transfer of immobilized biocatalysts affected the oxidation reaction (the internal effectiveness factor η < 1) but was not the rate-limiting step if Thiele modulus 1 > φ > 0.3. The optimal immobilization conditions for 3-HP biocatalysis was sodium alginate 40 g/L, gel beads diameter 1 mm, cross-linkage time 2 h and 0.1mM FeCl. Immobilized cells showed promising substrate tolerance, pH stability, thermal stability and storability. After 5 cycles of reaction, 3-HP molar yield of immobilized beads was retained to 80.26%, and 66.95 g/L 3-HP were produced from 70 g/L 1, 3-PDO. The biocatalysis process of immobilized cells introduced in this study may provide an economical and efficiency alternative route for practical production of 3-HP. [ABSTRACT FROM AUTHOR]

Some species of acetic acid bacteria (AAB) play relevant roles in the metabolism and physiology of Drosophila spp. and in some cases convey benefits to their hosts. The pest Drosophila suzukii harbors a set of AAB similar to those of other Drosophila species. Here, we investigate the potential to exploit the ability of AAB to produce volatile substances that attract female D. suzukii. Using a two-way olfactometer bioassay, we investigate the preference of D. suzukii for strains of AAB, and using solid-phase microextraction gas chromatography-mass spectrometry we specifically characterize their volatile profiles to identify attractive and non-attractive components produced by strains from the genera Acetobacter, Gluconobacter, and Komagataeibacter. Flies had a preference for one strain of Komagataeibacter and two strains of Gluconobacter. Analyses of the volatile profiles from the preferred Gluconobacter isolates found that acetic acid is distinctively emitted even after 2 days of bacterial growth, confirming the relevance of this volatile in the profile of this isolate for attracting flies. Analyses of the volatile profile from the preferred Komagataeibacter isolate showed that a different volatile in its profile could be responsible for attracting D. suzukii. Moreover, variation in the concentration of butyric acid derivatives found in some strains may influence the preference of D. suzukii. Our results indicate that Gluconobacter and Komagataeibacter strains isolated from D. suzukii have the potential to provide substances that could be exploited to develop sustainable mass-trapping-based control approaches. [ABSTRACT FROM AUTHOR]

The aim of this study was to understand the correlation between ethanol resistance and characteristics of PQQ-dependent ADH in acetic acid bacteria. Two ethanol-tolerant strains, FY-24 and DY-5, identified as Acetobacter pasteurianus were isolated from Chinese vinegar Pei. FY-24 and DY-5 maintained the growth and fermentation ability with 12 % (v/v) ethanol at 37 °C, but A. pasteurianus AS1.41 (widely used in China) could only be resistant to 10 % ethanol. ADH activities of FY-24 (6.13 U/mg) and DY-5 (5.41 U/mg) were much higher than that of AS1.41 (1.57 U/mg) at 8 % ethanol. Using purified ADH, it was shown that the ADHs from FY-24 and DY-5 exhibited a higher ethanol tolerance as ethanol increasing from 10 to 40 %. The optimum ethanol concentration for ADHs of FY-24 and DY-5 was 10 %, but was 5 % for that of AS1.41. Additionally, ADHs from FY-24 and DY-5 exhibited a higher resistance to temperature and acetic acid than that of AS1.41. From the amino acid sequence of ADH subunits, a certain amount of residues were found in the ADHs of FY-24 and DY-5 (411th D and 731th N in subunit I, 170th D in subunit II and 40th G in subunit III), which were different from that of AS1.41. The difference in amino acid residues might partly relate to the ethanol tolerance. Our results suggested that FY-24 and DY-5 could be developed for high ethanol acetic acid fermentation. [ABSTRACT FROM AUTHOR]

Classical studies concerning ' Acetobacter xylinum' focus on bacterial cellulose 'BC' yield and rate in broth, after a long period of incubation (7-14 days). Such observations do not highlight bacterial physiology in the first incubation hours and its impact on BC production. In this study, the growth of a wild strain of Acetobacter was monitored in the first incubation hours. We showed the presence of two different physiologies; the first extends from the incubation moment till the formation of a sparse BC. Sparse BC modifies surface viscosity, and stabilizes hydrodynamic conditions to initiate compact BC production that marks the second physiology. Two containers, of different shapes, were used to confirm our findings, one of which is a culture tube with high drift currents on the broth-air interface, and the other is a conical flask with more stable hydrodynamic conditions at the culture's surface. We showed that Acetobacter always follows two physiologies independent of the container shape. Logistic model, FTIR, XRD and SEM analysis are used to confirm the results. [ABSTRACT FROM AUTHOR]

The Acetobacteraceae family of the class Alpha Proteobacteria is comprised of high sugar and acid tolerant bacteria. The Acetic Acid Bacteria are the economically most significant group of this family because of its association with food products like vinegar, wine etc. Acetobacteraceae are often hard to culture in laboratory conditions and they also maintain very low abundances in their natural habitats. Thus identification of the organisms in such environments is greatly dependent on modern tools of molecular biology which require a thorough knowledge of specific conserved gene sequences that may act as primers and or probes. Moreover unconserved domains in genes also become markers for differentiating closely related genera. In bacteria, the 16S rRNA gene is an ideal candidate for such conserved and variable domains. In order to study the conserved and variable domains of the 16S rRNA gene of Acetic Acid Bacteria and the Acetobacteraceae family, sequences from publicly available databases were aligned and compared. Near complete sequences of the gene were also obtained from Kombucha tea biofilm, a known Acetobacteraceae family habitat, in order to corroborate the domains obtained from the alignment studies. The study indicated that the degree of conservation in the gene is significantly higher among the Acetic Acid Bacteria than the whole Acetobacteraceae family. Moreover it was also observed that the previously described hypervariable regions V1, V3, V5, V6 and V7 were more or less conserved in the family and the spans of the variable regions are quite distinct as well. [ABSTRACT FROM AUTHOR]

Microbially influenced corrosion (MIC) is a costly problem that impacts hydrocarbon production and processing equipment, water distribution systems, ships, railcars, and other types of metallic infrastructure. In particular, MIC is known to cause considerable damage to hydrocarbon fuel infrastructure including production, transportation, and storage systems, often times with catastrophic environmental contamination results. As the production and use of alternative fuels such as fuel-grade ethanol (FGE) increase, it is important to consider MIC of engineered materials exposed to these 'newer fuels' as they enter existing infrastructure. Reports of suspected MIC in systems handling FGE and water prompted an investigation of the microbial diversity associated with these environments. Small subunit ribosomal RNA gene pyrosequencing surveys indicate that acetic-acid-producing bacteria ( Acetobacter spp. and Gluconacetobacter spp.) are prevalent in environments exposed to FGE and water. Other microbes previously implicated in corrosion, such as sulfate-reducing bacteria and methanogens, were also identified. In addition, acetic-acid-producing microbes and sulfate-reducing microbes were cultivated from sampled environments containing FGE and water. Results indicate that complex microbial communities form in these FGE environments and could cause significant MIC-related damage that may be difficult to control. How to better manage these microbial communities will be a defining aspect of improving mitigation of global infrastructure corrosion. [ABSTRACT FROM AUTHOR]

Acetic acid bacterial strains were investigated for their ability to grow in aerobic and anaerobic sourdoughs (dough yield = 500) produced from wheat, whole wheat, spelt and rye flour and to produce effectual levels of exopolysaccharides (EPS) within 48 h of fermentation. The strains Kozakia ( K.) baliensis DSM 14400 and Neoasaia ( N.) chiangmaiensis NBRC 101099 were chosen. Both strains remained in aerobic doughs produced with any of the tested flours. For EPS optimization, 50, 75 and 100 g/l sucrose (sucrose) were added to the doughs and the parameters EPS, pH value, sucrose, acetic acid and gluconic acid were analysed. Results were subjected to statistical data analysis. In sucrose-enriched spelt dough, K. baliensis reached up to 49 g/kg EPS, followed by whole wheat (33 g/kg), wheat and rye dough (32-36 g/kg). N. chiangmaiensis produced 24-29 g/kg EPS in spelt and whole wheat doughs. EPS formation was positively correlated with start sucrose dosage. In contrast to this, a rather negative relation between acetic acid formation and start sucrose was found for both strains, and a positive relation with fermentation time. In spelt doughs, K. baliensis and N. chiangmaiensis produced up to 100 and 21-38 mM/kg acetic acid, respectively. Formation of gluconic acid was positively correlated with start sucrose dosage. K. baliensis produced at maximum 165 mM/kg flour and N. chiangmaiensis at maximum 119 mM/kg flour. Remaining sucrose contents were always positively correlated with start sucrose dosage, whereby both tested strains reached remaining sucrose amounts below 50 g/kg. A subsequent experiment with K. baliensis in backslopped spelt dough showed that this strain can remain in the dough over at least 8 days. [ABSTRACT FROM AUTHOR]

The anaerobic, acetogenic bacterium Acetobacterium woodii grows on hydrogen and carbon dioxide and uses the Wood-Ljungdahl pathway to fix carbon but also to synthesize ATP. The free energy change of acetogenesis from H + CO allows for synthesis of only a fraction of an ATP under environmental conditions, and A. woodii is clearly a paradigm for microbial life under extreme energy limitation. However, it was unknown how much energy is required to make ATP under these conditions. In the present study, we determined the phosphorylation potential in cells metabolizing three different acetogenic substrates. It accounts to 37.9 ± 1.3 kJ/mol ATP during acetogenesis from fructose, 32.1 ± 0.3 kJ/mol ATP during acetogenesis from H + CO and 30.2 ± 0.9 kJ/mol ATP during acetogenesis from CO, the lowest phosphorylation potential ever described. The physiological consequences in terms of energy conservation under extreme energy limitation are discussed. [ABSTRACT FROM AUTHOR]

The asymmetric reduction of ethyl acetoacetate (EAA) to ethyl ( R)-3-hydroxybutyrate [( R)-EHB] using immobilized Acetobacter sp. CCTCC M209061 cells was successfully conducted in a hydrophilic ionic liquid (IL)-containing system. The best one of all the tested watermiscible ILs was 1-(hydroxyethyl)-3-methylimidazolium hydrochloride (COHMIM·Cl). In COHMIM·Cl-aqueous buffer hybrid system, it was found that the optimal IL concentration, substrate and co-substrate concentration, reaction temperature, buffer pH and shaking rate were 0.5mol/L, 45 mmol/L, 80 mmol/L, 35°C, pH 5.5 and 200 rpm, respectively. Under the optimized reaction conditions, the initial reaction rate, the yield and the product e.e. reached 4.90 µmol/min, 95.3 and > 99.0%, respectively, which were much higher than the corresponding values reported previously. The efficient biocatalytic process mediated by the immobilized cells was feasible on 500 mL preparative scale, and the biocatalysts showed good operational stability and could be recycled for at least 10 batches. [ABSTRACT FROM AUTHOR]

The acsD gene is involved in cellulose biosynthesis among the Acetobacter species. In the current study, we created an acsD disruption mutant in the acsABCD cellulose synthase operon of Gluconacetobacter xylinus and characterized the resulting cellulose to aid in providing insight into the function of the acsD gene. Both the wild type G. xylinus AY201 (derivative of Gluconacetobacter hansenii ATCC 23769) and the acsD disruption mutant produced crystalline cellulose I microfibrils. The cellulose produced by both appeared to be synthesized from an aggregate of pores known as a linear terminal complex; however the total cellulose synthesized was 10 % that of the wild type G. xylinus AY201. TEM observations of the acsD disruption mutant confirmed that microfibrils and bundles of microfibrils were similar in size to the G. xylinus AY201 wild type; however, the final ribbon dimensions were narrower (53.4 ± 13.1 nm wt, vs. 28.2 ± 8.2 nm). Additional TEM observations of the mutant cells incubated at 4 °C revealed an abnormal linear terminal complex orientation whereby the resulting band material could be observed in a transverse orientation as well as longitudinally to the long axis of the cell. Taken together, these data strongly suggest that acsD aids in the proper orientation of the linear terminal complexes along the longitudinal axis of the cell indicating the AcsD protein is involved in the final level of the hierarchical assembly of cellulose resulting in highly efficient cellulose synthesis. [ABSTRACT FROM AUTHOR]

Bacteria of the species Gluconobacter oxydans are applied in the industrial production of dihydroxyacetone (DHA) via glycerol oxidation. The major problem of this biotransformation involves process inhibition by substrate and/or product. Improper initial concentration of glycerol and increasing DHA concentration may inhibit the metabolic activity of bacterial cells and impede further course of the reaction. An attempt was, therefore, undertaken in this study to determine which concentrations of glycerol (30, 50, 70, 100 g L) and DHA (10-100 g L) may inhibit the growth of acetic acid bacteria of G. oxydans ATCC 621 species. Cultures of this strain were run in the Bioscreen C MBR apparatus on experimental culture media with various initial concentrations of glycerol and DHA. Analyses were also carried out to examine the impact of pH (5.0, 7.0, 8.0) of glycerol-containing culture media on cell growth of the analyzed strain G. oxydans. None of the applied substrate concentrations was inhibiting cellular divisions of G. oxydans bacteria. The initial glycerol concentrations that enabled rapid cellular divisions reached 50 g L in the medium with pH 5.0 (coefficient of specific growth rate μ = 0.0550) and 70 g L in the medium with pH 7.0 ( μ = 0.0556). DHA was shown to inhibit the mitotic activity of G. oxydans bacteria even at low concentrations (20-30 g L), whereas at the concentration of 70 g L, it made cell divisions impossible. The applied pH values of the culture media did not inhibit the growth of G. oxydans strain. [ABSTRACT FROM AUTHOR]

Camponotus is the second largest ant genus and known to harbor the primary endosymbiotic bacteria of the genus Blochmannia. However, little is known about the effect of diet and environment changes on the gut bacterial communities of these ants. We investigated the intestinal bacterial communities in the lab-raised and field-collected ants of Camponotus fragilis which is found in the southwestern United States and northern reaches of Mexico. We determined the difference of gut bacterial composition and distribution among the crop, midgut, and hindgut of the two types of colonies. Number of bacterial species varied with the methods of detection and the source of the ants. Lab-raised ants yielded 12 and 11 species using classical microbial culture methods and small-subunit rRNA genes (16S rRNAs) polymerase chain reaction-restriction fragment-length polymorphism analysis, respectively. Field-collected ants yielded just 4 and 1-3 species using the same methods. Most gut bacterial species from the lab-raised ants were unevenly distributed among the crop, midgut, and hindgut, and each section had its own dominant bacterial species. Acetobacter was the prominent bacteria group in crop, accounting for about 55 % of the crop clone library. Blochmannia was the dominant species in midgut, nearly reaching 90 % of the midgut clone library. Pseudomonas aeruginosa dominated the hindgut, accounting for over 98 % of the hindgut clone library. P. aeruginosa was the only species common to all three sections. A comparison between lab-raised and field-collected ants, and comparison with other species, shows that gut bacterial communities vary with local environment and diet. The bacterial species identified here were most likely commensals with little effect on their hosts or mild pathogens deleterious to colony health. [ABSTRACT FROM AUTHOR]

Nanocomposites of poly(vinyl alcohol) (PVA) reinforced with bacterial cellulose (BC) were bioproduced by Gluconacetobacter genus bacteria. BC was grown from a culture medium modified with water-soluble PVA to allow in situ assembly and production of a novel nanocomposite that displayed synergistic property contributions from the individual components. Chemical crosslinking with glyoxal was performed to avoid the loss of PVA matrix during purification steps and to improve the functional properties of composite films. Reinforcement with BC at 0.6, 6 and 14 wt% content yielded nanocomposites with excellent mechanical, thermal and dimensional properties as well as moisture stability. Young's modulus and strength at break increased markedly with the reinforcing BC: relative to the control sample (in absence of BC), increases of 15, 165 and 680 % were determined for nanocomposites with 0.6, 6 and 14 % BC loading, respectively. The corresponding increase in tensile strengths at yield were 1, 12 and 40 %, respectively. The results indicate an exceptional reinforcing effect by the three-dimensional network structure formed by the BC upon biosynthesis embedded in the PVA matrix and also suggest a large percolation within the matrix. Bonding (mainly hydrogen bonding) and chemical crosslinking between the reinforcing phase and matrix were the main contributions to the properties of the nanocomposite. [ABSTRACT FROM AUTHOR]

Seeking high strength vinegar fermentation by acetic acid bacteria (AAB) is still the mission of vinegar producers. AAB alcohol respiratory chain, located on intracellular membrane, is directly responsible for vinegar fermentation. In the semi-continuous vinegar fermentation by Acetobacter pasteurianus CICIM B7003, acetification rate showed positive correlation with the activity of the enzymes in alcohol respiratory chain. Aiming at achieving high strength fermentation process, a series of trials were designed to raise the activity of AAB alcohol respiratory chain. Finally, acetification was enhanced by adding some precursors (ferrous ions and β-hydroxybenzoic acid) of alcohol respiration associated factors and increasing aeration rate (0.14 vvm). As final result, average acetification rate has been raised to 2.29 ± 0.02 g/L/h, which was 28.7% higher than the original level. Simultaneously, it was found that the oxidization of alcohol into acetic acid in AAB cells was improved by well balancing of three factors: enzyme activity in alcohol respiratory chain, precursor of ubiquinone biosynthesis, and aeration rate. [ABSTRACT FROM AUTHOR]

In this study, typical niches of acetic acid bacteria were screened for isolation of cellulose producer strains. Hestrin Schramm broth was used as enrichment and production media. Only nine out of 329 isolates formed thick biofilms on liquid surface and were identified as potential cellulose producers. Physiological and biochemical tests proved that all cellulose producers belonged to Gluconacetobacter genus. Most productive and mutation-resistant strain was subjected to 16S rRNA sequence analysis and identified as Gluconacetobacter hansenii P2A due to 99.8 % sequence similarity. X-ray diffraction analysis proved that the biofilm conformed to Cellulose I crystal structure, rich in I mass fraction. Static cultivation of G. hansenii P2A in HS medium resulted with 1.89 ± 0.08 g/l of bacterial cellulose production corresponding to 12.0 ± 0.3 % yield in terms of substrate consumption. Shaking and agitation at 120 rpm aided in enhancement of the amount and yield of produced cellulose. Productivity and yield reached up to 3.25 ± 0.11 g/l and 17.20 ± 0.14 % in agitated culture while a slight decrease from 78.7 % to 77.3 % was observed in the crystallinity index. [ABSTRACT FROM AUTHOR]

Members of the Acetobacter pasteurianus are popular acetic acid bacteria (AAB) for the production of vinegar. Neither phenotypic nor the most frequently applied genotypic marker (16S ribosomal DNA) provides sufficient resolution for accurate identification of the AAB strains. In this study, the gyrB gene was used for species discrimination by direct DNA sequencing and as marker in a species-specific PCR assay. All examined A. pasteurianus strains were clearly distinguished from the closely related species by comparative sequence analysis of the gyrB gene. The average sequence similarity for the gyrB gene (82.2 %) among type strains was significantly lower than that of the 16S rRNA sequence (98.2 %). Therefore, the gyrB gene can be proposed as an additional molecular marker for A. pasteurianus and related taxa that provides higher resolution than 16S rRNA. In addition, the species-specific primers were also developed based on the gyrB and 16S rRNA gene sequences, which were then employed for PCR using the template DNA of Acetobacter strains. The PCR primer pairs were shown to be specific for A. pasteurianus, A. peroxydans and papayae. Our data indicate that the phylogenetic relationships in the A. pasteurianus group are easily resolved by direct sequencing of the gyrB gene and combined with species-specific PCR assays. [ABSTRACT FROM AUTHOR]

Xanthine oxidase (XO) acts at the end of a catabolic sequence of purine nucleotide metabolism in humans and a few other uricotelic species. The EtOAc layer showed strong xanthine oxidase inhibitory activity (~99% XO inhibition). Fraction 9 (18% XO inhibition) was purified by prep. TLC (CH SB 2 sb Cl SB 2 sb -MeOH, 12:1) to give I p i -hydroxybenzoic acid ( B 3 b ) (3.6 mg) and gallic acid 4-methyl ether ( B 4 b ) (2.5 mg). [Extracted from the article]

Metabolic flux analysis was used to reveal the metabolic distributions in Gluconacetobacter xylinus (CGMCC no. 2955) cultured on different carbon sources. Compared with other sources, glucose, fructose, and glycerol could achieve much higher bacterial cellulose (BC) yields from G. xylinus (CGMCC no. 2955). The glycerol led to the highest BC production with a metabolic yield of 14.7 g/mol C, which was approximately 1.69-fold and 2.38-fold greater than that produced using fructose and glucose medium, respectively. The highest BC productivity from G. xylinus CGMCC 2955 was 5.97 g BC/L (dry weight) when using glycerol as the sole carbon source. Metabolic flux analysis for the central carbon metabolism revealed that about 47.96 % of glycerol was transformed into BC, while only 19.05 % of glucose and 24.78 % of fructose were transformed into BC. Instead, when glucose was used as the sole carbon source, 40.03 % of glucose was turned into the by-product gluconic acid. Compared with BC from glucose and fructose, BC from the glycerol medium showed the highest tensile strength at 83.5 MPa, with thinner fibers and lower porosity. As a main byproduct of biodiesel production, glycerol holds great potential to produce BC with superior mechanical and microstructural characteristics. [ABSTRACT FROM AUTHOR]

The purification and characterization of an extracellular levansucrase enzyme produced by novel nitrogen-fixer Acetobacter nitrogenifigens strain RG1 is described. Culture conditions were optimized for maximum levansucrase production. Levansucrase purified to homogeneity by tenfold purification has a molecular weight of 65 kDa, contained four cysteine residues, polymerized raffinose and was stable for 21 days at pH 6.0 when stored at 4 °C or −20 °C but was vulnerable to DTT and β-mercaptoethanol. Interestingly, this enzyme showed enhanced hydrolytic and polymerization activity in the presence of mercuric ion which, to our knowledge, is the first report for any levansucrase enzyme characterized so far. Evidences obtained from Native PAGE, tryptophan fluorescence study and activity measurements at different temperatures and in the presence of thiol modifying agents, show that mercuric ion stabilizes the enzyme. Levan, synthesized by the enzyme, has a molecular weight of 7,080 kDa and was shown to be a homopolymer of fructose. [ABSTRACT FROM AUTHOR]

Microbes have a fascinating repertoire of bioenergetic enzymes and a huge variety of electron transport chains to cope with very different environmental conditions, such as different oxygen concentrations, different electron acceptors, pH and salinity. However, all these electron transport chains cover the redox span from NADH + H as the most negative donor to oxygen/HO as the most positive acceptor or increments thereof. The redox range more negative than −320 mV has been largely ignored. Here, we have summarized the recent data that unraveled a novel ion-motive electron transport chain, the Rnf complex, that energetically couples the cellular ferredoxin to the pyridine nucleotide pool. The energetics of the complex and its biochemistry, as well as its evolution and cellular function in different microbes, is discussed. [ABSTRACT FROM AUTHOR]

Purpose: Soil microorganisms directly affect the growth of plants. Especially, plant growth-promoting rhizobacteria (PGPR) play an important role in plant growth. There are many studies about the effects of different fertilization treatments on soil microbial community structure; however, the effects on PGPR, including indole-3-acetic acid (IAA)-producing bacteria have not been previously reported. The objective of this study is to determine the effects of different types of fertilizers on IAA-producing bacteria. Materials and methods: The field trial was completed in the North China with a winter wheat and summer corn rotation system. IAA-producing bacteria were screened from soil treated with different fertilizer (non-nitrogen fertilizer (CK), controlled-release fertilizer (CR), chemical fertilizer (CF), and organic fertilizer (OF)) which was established in September 2005. Quantity of IAA produced by bacteria was determined by spectrophotometer. IAA-producing bacteria were identified based on 16S rDNA sequence. Community structures and phylogenetic relationships of IAA-producing bacteria were analyzed by online Basic Local Alignment Search Tool search engine, biosoftware of DNAMAN and Molecular Evolutionary Genetics Analysis. Results and discussion: Compared with CK treatment, CF and CR treatment increased soil pH values, while OF treatment decreased pH. The three types of fertilizers all increased soil organic carbon and total nitrogen, with OF treatment causing the significant increase. Soils treated with OF or CR fertilizer could significantly increase the number of culturable bacteria compared with CF or CK treatment. Fifty-three IAA-producing bacteria (14 strains from CK, nine from CF, eight from CR, and 22 from OF) were identified based on 16S rDNA sequence. The Shannon-Weiner index of IAA-producing bacteria isolated from CK and OF (2.06 and 2.45, respectively) was significantly higher than those from CF and CR (0.50 and 0.95, respectively). Arthrobacter sp. was the most prevalent group of IAA-producing bacteria. Conclusions: The fertilizers increased soil organic carbon and total nitrogen, particularly the organic fertilizers. Controlled-release fertilizers and organic fertilizers can promote growth of soil-culturable bacteria and IAA-producing bacteria. These may be reasons why organic fertilizers and controlled-release fertilizers can promote crop growth. Different fertilization treatments affected IAA yield mainly through modifying the quantities of microorganisms, rather than changing the IAA-producing ability of the same microorganisms. Pedobacter sp. which can produce IAA has not been described previously. [ABSTRACT FROM AUTHOR]

The aim of the present study was to search for a rapid and reliable method to enumerate viable acetic acid bacteria (AAB) and to identify to genera and species level AAB isolates from vinegars in full acetic fermentation elaborated by the submerged method from cider, wine and spirit ethanol in industrial bioreactors. Results showed that the rapid epifluorescence staining method using the LIVE/DEAD BacLight bacterial viability kit and direct counts in Neubauer chamber rendered consistent and reliable data for viable cell counts of bacteria in all the studied vinegars. A linear correlation was shown between viable cell counts and fermentation rates. The highest fermentation rates and viable cell counts were found in cider vinegars, whereas spirit vinegars showed the lowest values for both parameters. Eighty-four AAB pure isolates were recovered from 41 different vinegar samples and were submitted to DNA extraction. PCR amplification of the 16S–23S intergenic spacer region of rDNA and subsequent sequencing were carried out to identify isolates to species level. Results showed that Gluconacetobacter europaeus was the predominant cultivable species, appearing in 79% of the total isolates. This was the unique species found in spirit vinegars, and this is the first time that AAB from spirit vinegars are taxonomically identified. Ga. europaeus was as well the predominant cultivable species in white wine vinegars. Cider vinegars presented the highest variability of species: Ga. europaeus (35.3% appearance among cultivable isolates), Ga. xylinus (35.3%), Acetobacter pasteurianus (17.6%) and Ga. hansenii (11.8%). Red wine vinegars showed cultivable isolates of the species Ga. xylinus (71.4%) and Ga. europaeus (28.6%). Summarising, both described methods for AAB enumeration and taxonomical identification proved to be fast and reliable methods, and results revealed Ga. europaeus as the cultivable major species in vinegars in full fermentation conducted by the submerged method, suggesting that Ga. europaeus strains can constitute excellent starter cultures for the elaboration of vinegars by the submerged method. [ABSTRACT FROM AUTHOR]

The formation of composites based on the cellulose Acetobacter xylinum and calcium phosphates has been investigated using X-ray diffraction, electron diffraction, electron microscopy, energy-dispersive analysis, and differential scanning calorimetry. It has been demonstrated that the planar morphology of calcium phosphate nanoparticles capable of interacting with nanofibrils of the cellulose matrix is an important factor providing interfacial contacts in the formation of organic-inorganic composite materials. It has been established that magnesium-containing calcium phosphates represent two-phase systems consisting of calcium magnesium phosphate CaMg(PO) (whitlockite) and hydroxyapatite Ca(PO)(OH). The biocompatibility of the composite materials based on two-phase calcium phosphate systems and the temperature range of their stability (∼20–250°C) determined by the thermal stability of the organic component have been investigated. [ABSTRACT FROM AUTHOR]