Introduction Historical Outline Structure of BC Chemical Analysis and Detection Occurrence Physiological Function Biosynthesis of BC Synthesis of the Cellulose Precursor Cellulose Synthase Mechanism of Biosynthesis Genetic Basis of Cellulose Biosynthesis Regulation of Bacterial Cellulose Synthesis Soluble Polysaccharides Synthesized by A. xylinum Role of Endo‐ and Exocellulases Synthesized by A. xylinum Biodegradation of BC Biotechnological Production Isolation from Natural Sources and Improvement of BC‐producing Strains Fermentation Production In vitro Biosynthesis Chemo‐enzymatic Synthesis Production Processes Expected to be Applied in the Future Recovery and Purification Properties Applications Technical Applications Medical Applications Food Applications Miscellaneous Uses Patents Outlook and Perspectives

Ethanol exerts a strong positive effect on the cellulose yields from the widely exploited microbial producers of the Komagataeibacter genus. Ethanol is postulated to provide an alternative energy source, enabling effective use of glucose for cellulose biosynthesis rather than for energy acquisition. In this paper, we investigate the effect of ethanol supplementation on the global gene expression profile of Komagataeibacter xylinus E25 using RNA sequencing technology (RNA-seq). We demonstrate that when ethanol is present in the culture medium, glucose metabolism is directed towards cellulose production due to the induction of genes related to UDP-glucose formation and the repression of genes involved in glycolysis and acetan biosynthesis. Transcriptional changes in the pathways of cellulose biosynthesis and c-di-GMP metabolism are also described. The transcript level profiles suggest that Schramm-Hestrin medium supplemented with ethanol promotes bacterial growth by inducing protein biosynthesis and iron uptake. We observed downregulation of genes encoding transposases of the IS 110 family which may provide one line of evidence explaining the positive effect of ethanol supplementation on the genotypic stability of K. xylinus E25. The results of this study increase knowledge and understanding of the regulatory effects imposed by ethanol on cellulose biosynthesis, providing new opportunities for directed strain improvement, scaled-up bionanocellulose production, and wider industrial exploitation of the Komagataeibacter species as bacterial cellulose producers. Electronic supplementary material The online version of this article (10.1007/s00253-019-09904-x) contains supplementary material, which is available to authorized users.

Two extracellular tannin acyl hydrolases (TAH I and TAH II) produced by an Antarctic filamentous fungus Verticillium sp. P9 were purified to homogeneity (7.9- and 10.5-fold with a yield of 1.6 and 0.9%, respectively) and characterized. TAH I and TAH II are multimeric (each consisting of approximately 40 and 46 kDa sub-units) glycoproteins containing 11 and 26% carbohydrates, respectively, and their molecular mass is approximately 155 kDa. TAH I and TAH II are optimally active at pH of 5.5 and 25 and 20 degrees C, respectively. Both the enzymes were activated by Mg(2+)and Br(-) ions and 0.5-2.0 M urea and inhibited by other metal ions (Zn(2+), Cu(2+), K(+), Cd(2+), Ag(+), Fe(3+), Mn(2+), Co(2+), Hg(2+), Pb(2+) and Sn(2+)),[Formula: see text] anions, Tween 20, Tween 60, Tween 80, Triton X-100, sodium dodecyl sulphate, beta-mercaptoethanol, alpha-glutathione and 4-chloromercuribenzoate. Both tannases more efficiently hydrolyzed tannic acid than methyl gallate. E (a) of these reactions and temperature dependence (at 0-30 degrees C) of k (cat), k (cat)/K (m), DeltaG*, DeltaH* and DeltaS* for both the enzymes and substrates were determined. The k (cat) and k (cat)/K (m) values (for both the substrates) were considerably higher for the combined preparation of TAH I and TAH II.

An extracellular serine proteinase, lap2, from the psychrophilic antarctic yeast Leucosporidium antarcticum 171 was purified to homogeneity and characterized. The enzyme is a glycoprotein with a molecular mass of 34.4 kDa and an isoelectric point of pH 5.62. The proteinase is halotolerant, and its activity and stability are dependent neither on Ca(2+) nor on other metal ions. Lap2 is a true psychrophilic enzyme because of low optimal temperature (25 degrees C), poor thermal stability, relatively small values of free energy, enthalpy and entropy of activation, and high catalytic efficiency at 0-25 degrees C. The 35 N-terminal amino acid residues of lap2 have homology with subtilases of the proteinase K subfamily (clan SB, family S8, subfamily C). The proteinase lap2 is the first psychrophilic subtilase in this family.

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A psychrotrophic bacterium producing a cold-adapted esterase upon growth at low temperatures was isolated from the alimentary tract of Antarctic krill Euphasia superba Dana, and classified as Pseudoalteromonas sp. strain 643A. A genomic DNA library of strain 643A was introduced into Escherichia coli TOP10F', and screening on tributyrin-containing agar plates led to the isolation of esterase gene. The esterase gene (estA, 621 bp) encoded a protein (EstA) of 207 amino acid residues with molecular mass of 23,036 Da. Analysis of the amino acid sequence of EstA suggests that it is a member of the GDSL-lipolytic enzymes family. The purification and characterization of native EstA esterase were performed. The enzyme displayed 20-50% of maximum activity at 0-20 degrees C. The optimal temperature for EstA was 35 degrees C. EstA was stable between pH 9 and 11.5. The enzyme showed activity for esters of short- to medium-chain (C(4) and C(10)) fatty acids, and exhibited no activity for long-chain fatty acid esters like that of palmitate and stearate. EstA was strongly inhibited by phenylmethylsulfonyl fluoride, 2-mercaptoethanol, dithiothreitol and glutathione. Addition of selected divalent ions e.g. Mg(2+), Co(2+) and Cu(2+) led to the reduction of enzymatic activity and the enzyme was slightly activated ( approximately 30%) by Ca(2+) ions.

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The digestibility of cellulosic pulps derived by the sulfate process was assessed using commercial multienzyme preparations. Poplar wood pulps of relatively low lignin contents (Kappa numbers of 15.4-24.2), birch, beech and pine wood pulps (Kappa numbers of 25.8-31.4), and wheat straw pulp (Kappa number of 29.5) were efficiently hydrolyzed by a commercial preparation NS-22086 from Novozymes, containing cellulases and xylanases. At around 1.3 % (w/w) substrate concentration, yields of glucose from the poplar pulps were around 80 % on a dry weight (d.w.) basis while for the other four pulps they varied between approximately 70 % (for pine pulp) and 78 % d.w. (for beech and wheat straw pulps). At around 7.4 % (w/w) poplar pulp (Kappa number of 24.2) concentration, glucose yield was around 61 % d.w. The NS-22086 preparation almost completely saccharified fines from a paper mill (around 74 % glucose yields on a dry weight basis) while digestion of poplar chips (particle size of 1.6-2.0 mm) and wheat straw chaff (particle size up to 6 mm) yielded around 5.3 and 14 % d.w. glucose, respectively (total reducing sugars yields of around 16 and 23 % d.w., respectively). These results show that plant biomass may be efficiently converted to glucose-rich hydrolysates by a two-step processing, consisting of kraft pulping followed by treatment with endo-and exo-type cellulases and hemicellulases. Glucose-rich hydrolysates may be also obtained by enzymatic digestion of fines from paper mills.