Xanthan production by Xanthomonas campestris using whey permeate medium

UV and Chemically Induced Halomonas smyrnensis Mutants for Enhanced Levan Productivity

Halomonas smyrnensis AAD6^T is a moderately halophilic bacterium proven to be a powerful biotechnological tool with its ability to accumulate valuable biopolymers such as levan and poly(3-hydroxybutyrate) (PHB). Levan is a fructose homopolymer with β-2,6 fructofuranosidic linkages on the polymer backbone, and its distinctive applications in various industries such as food, pharmaceutical, medical, and chemical have been well-defined. On the other hand, PHB is a promising raw material to produce biodegradable plastics. Although it was shown in our previous studies that H. smyrnensis AAD6^T exhibits one of the highest conversion yields of sucrose to levan reported to date, novel strategies are required to overcome high costs of levan production. In this study, we aimed at increasing levan productivity of H. smyrnensis AAD6^T cultures using random mutagenesis techniques combined (i.e., ethyl methanesulfate treatment and/or ultraviolet irradiation). After several consecutive treatments, mutant strains BAE2, BAE5 and BAE6 were selected as efficient levan producers, as BAE2 standing out as the most efficient one not only in sucrose utilization and levan production rates, but also in final PHB concentrations. The mutants' whole genome sequences were analysed to determine the mutations occurred. Several mutations in genes related to central carbon metabolism and osmoregulation were found. Our results suggest that random mutagenesis can be a facile and efficient strategy to enhance the performance of extremophiles in adverse conditions.

Innovations in CAZyme gene diversity and its modification for biorefinery applications

For sustainable growth, concept of biorefineries as recourse to the "fossil derived" energy source is important. Here, the Carbohydrate Active enZymes (CAZymes) play decisive role in generation of biofuels and related sugar-based products utilizing lignocellulose as a carbon source. Given their industrial significance, extensive studies on the evolution of CAZymes have been carried out. Various bacterial and fungal organisms have been scrutinized for the development of CAZymes, where advance techniques for strain enhancement such as CRISPR and analysis of specific expression systems have been deployed. Specific Omic-based techniques along with protein engineering have been adopted to unearth novel CAZymes and improve applicability of existing enzymes. In-Silico computational research and functional annotation of new CAZymes to synergy experiments are being carried out to devise cocktails of enzymes for use in biorefineries. Thus, with the establishment of these technologies, increased diversity of CAZymes with broad span of functions and applications is seen.

Proteomic Analysis of the Xanthan-Degrading Pathway of Microbacterium sp. XT11

Xanthan, a highly stable polysaccharide which is not easily degraded by most microorganisms, contains a cellulosic backbone with trisaccharide side chains composed of mannosyl-glucuronyl-mannose attached α-1,3 to alternating glucosyl residues. Different digestion strategies were first applied to demonstrate the complexity about the proteomes of Microbacterium sp. XT11 in xanthan medium and glucose medium. Significantly up-regulated proteins induced by xanthan were screened out by the label-free quantitation of the proteomes of Microbacterium sp. XT11 in xanthan medium and glucose medium. Consequently, 2746 and 2878 proteins were identified in proteomes of Microbacterium sp. XT11 in xanthan medium and glucose medium individually, which represent 80.6 and 84.4% of total protein dataset predicted to be expressed by the gene. In the list of 430 induced proteins containing the proteins specifically expressed or up-regulated in xanthan medium, 19 proteins involved in carbohydrate-active enzymes database and 38 proteins annotated with transporter activity were critical in the degrading pathway of xanthan. Four CAZymes (GH3, GH38, GH9, and PL8) and one ABC transporter (LX1-1GL001097) were verified with quantitative real-time polymerase chain reaction. Four CAZymes (GH3, GH38, GH9, and PL8) were further verified with the enzyme assay. This study suggests a xanthan-degrading pathway in Microbacterium sp. XT11, and other potential xanthan degradation-related proteins still need further investigation.

Valorisation of chicken feathers for xanthan gum production using Xanthomonas campestris MO-03

Xanthan gum is an important commercial polysaccharide produced by Xanthomonas species. In this study, xanthan production was investigated using a local isolate of Xanthomonas campestris MO-03 in medium containing various concentrations of chicken feather peptone (CFP) as an enhancer substrate. CFP was produced with a chemical process and its chemical composition was determined. The addition of CFP (1–8 g/l) increased the conversion of sugar to xanthan gum in comparison with the control medium, which did not contain additional supplements. The highest xanthan production (24.45 g/l) was found at the 6 g/l CFP containing control medium in 54 h. This value was 1.73 fold higher than that of control medium (14.12 g/l). Moreover, addition of CFP improved the composition of xanthan gum; the pyruvate content of xanthan was 3.86% (w/w), higher than that of the control (2.2%, w/w). The xanthan gum yield was also influenced by the type of organic nitrogen sources. As a conclusion, CFP was found to be a suitable substrate for xanthan gum production.

Effect of the novel functional fibre, polyglycoplex (PGX), on body weight and metabolic parameters: A systematic review of randomized clinical trials

BACKGROUND & AIMS

Hundreds of dietary supplements are marketed as weight loss pills, but the evidence for effectiveness for most is unproven. The objective of this review was to critically appraise and evaluate the evidence from published randomized clinical trials (RCTs) examining the effectiveness of polyglycoplex (PGX), a novel functional fibre, on body weight and metabolic parameters.

METHODS

We conducted electronic searches in Medline, Embase, Amed, Cinahl and The Cochrane Library. Only double-blinded RCTs were considered for inclusion. The reporting quality of included studies was assessed using the Cochrane criteria. Two reviewers independently determined eligibility, assessed the quality of reporting, and extracted the data.

RESULTS

We included four RCTs with a total of 217 participants. The RCTs varied in the quality of their reporting. The evidence from the RCTs suggested that PGX has no significant effects on body weight; however, significant reductions were noted for total and LDL cholesterol. Adverse events reported included diarrhea and abdominal bloating.

CONCLUSION

The evidence from available RCTs does not indicate that PGX intake causes reductions in body weight. PGX may cause reductions in total and LDL cholesterol. Few trials examining the effects of PGX have been conducted; they are characterized by small sample sizes, deficiencies in reporting quality, and are funded by a single manufacturer. Future clinical trials evaluating its effect should be adequately powered and better reported.

Production and purification of a novel xanthan lyase from a xanthan-degrading Microbacterium sp. strain XT11

A xanthan lyase was produced and purified from the culture supernatant of an excellent xanthan-modifying strain Microbacterium sp. XT11. Xanthan lyase was induced by xanthan but was inhibited by its structural monomer glucose. Its production by strain XT11 is much higher than that by all other reported strains. The purified xanthan lyase has a molecular mass of 110 kDa and a specific activity of 28.2 U/mg that was much higher than that of both Paenibacillus and Bacillus lyases. It was specific on the pyruvated mannosyl residue in the intact xanthan molecule, but about 50% lyase activity remained when xanthan was partially depyruvated. Xanthan lyase was optimally active at pH 6.0–6.5 and 40°C and alkali-tolerant at a high pH value of 11.0. The metal ions including K⁺, Ca²⁺, Na⁺, Mg²⁺, Mn²⁺, and Li⁺ strongly stimulated xanthan lyase activity but ions Zn²⁺ and Cu²⁺ were its inhibitor. Xanthan lyase should be a novel enzyme different from the other xanthan lyases ever reported.

Xanthan Gum Removal for 1H-NMR Analysis of the Intracellular Metabolome of the Bacteria Xanthomonas axonopodis pv. citri 306

Xanthomonas is a genus of phytopathogenic bacteria, which produces a slimy, polysaccharide matrix known as xanthan gum, which involves, protects and helps the bacteria during host colonization. Although broadly used as a stabilizer and thickener in the cosmetic and food industries, xanthan gum can be a troubling artifact in molecular investigations due to its rheological properties. In particular, a cross-reaction between reference compounds and the xanthan gum could compromise metabolic quantification by NMR spectroscopy. Aiming at an efficient gum extraction protocol, for a ¹H-NMR-based metabolic profiling study of Xanthomonas, we tested four different interventions on the broadly used methanol-chloroform extraction protocol for the intracellular metabolic contents observation. Lower limits for bacterial pellet volumes for extraction were also probed, and a strategy is illustrated with an initial analysis of X. citri’s metabolism by ¹H-NMR spectroscopy.