Optimization and Characterization of an Ultra-Thermostable, Acidophilic, Cellulase-Free Xylanase from a New Obligate Thermophilic Geobacillus thermoleovorans AKNT10 and its Application in Saccharification of Wheat Bran.

Microbial xylanases are enzymes of great importance due to their wide industrial applications, especially in the degradation of lignocellulosic biomass into fermentable sugars. This study aimed to describe the production optimization and partial characterization of an ultra-thermostable, acidophilic, cellulase-free xylanase from an obligate thermophilic eubacterium Geobacillus thermoleovorans strain-AKNT10 (Ac.No. LT158229) isolated from a hot-spring of Puga Valley located at an altitude of 4419 m in Ladakh, India. The optimization of cultural conditions improved enzyme yield by 10.49-fold under submerged fermentation. The addition of 1% (w/v) xylose induced the enzyme synthesis by ~ 165 and 371% when supplemented in the fermentation medium containing wheat bran (WB) 1 and 3%, respectively. The supplementation of sucrose reduced the xylanase production by ~ 25%. Results of partial characterization exhibited that xylanase was optimally active at pH 6.0 and 100 °C. Enzyme retained > 75%, > 83%, and > 84% of activity at 4 °C for 28 days, 100 °C for 60 min, and pHs 3-8 for 60 min, respectively. An outstanding property of AKNT10-xylanase, was the retention of > 71% residual activity at extreme conditions (121 °C and 15 psi pressure) for 15 min. Enzymatic saccharification showed that enzyme was also capable to liberate maximum reducing sugars within 4-8 h under optimized conditions thus it could be a potential candidate for the bioconversion of lignocellulosic biomass as well as other industrial purposes. To the best of our knowledge, this is the first report on such an ultra-thermo-pressure-tolerant xylanase optimally active at pH 6 and 100 °C from the genus Geobacillus.

Production of thermostable hydrolases (cellulases and xylanase) from Thermoascus aurantiacus RCKK: a potential fungus.

Thermophilic fungi are potential sources of thermostable enzymes and other value added products. Present study has focused on optimization of different physicochemical parameters for production of thermostable cellulases and xylanase by Thermoascus aurantiacus RCKK under SSF. Enzyme production was supported maximally on wheat bran fed with 20% inoculum, at initial pH 5, temperature 45 °C and moisture ratio 1:3. The supplementation of wheat bran with yeast extract, Tween-80 and glycine further improved enzyme titres (CMCase 88 IU/g, FPase 15.8 IU/g, ß-glucosidase 25.3 IU/g and xylanase 6,543 IU/g). The crude enzymes hydrolyzed phosphoric acid-swollen wheat straw, avicel and untreated xylan up to 74, 71 and 90%, respectively. In addition, T. aurantiacus RCKK produced antioxidants as fermentation by-products with significant %DPPH(∙) scavenging, FRAP and in vivo antioxidant capacity against H2O2-treated Saccharomyces cerevisiae. These capabilities show that it holds potential to exploit crop by-products for providing various commodities.

Enhanced production and extraction of phenolic compounds from wheat by solid-state fermentation with Rhizopus oryzae RCK2012.

Antioxidant phenolic compounds (PCs) are gaining popularity day by day for their health promoting properties. Wheat is a very good source of natural antioxidant PCs. In the present study, extraction of PCs was improved by solid-state fermentation (SSF) of wheat by Rhizopus oryzae RCK2012 which helped to release the bound compounds from matrix. Different extraction conditions such as solvent composition (water, methanol, 70% methanol, ethanol, 70% ethanol, acetone and 70% acetone), extraction temperature (30-60 °C), extraction time (15-90 min) and solid-to-solvent ratio (1:2.5 to 1:20, w/v) have been optimized for the extraction of PCs from R. oryzae fermented wheat. Maximum PCs were extracted by water at 40 °C within 45 min with solid-to-solvent ratio of 1:15 (w/v). Compositional analysis of PCs was carried out by UPLC and TLC. Improved ABTS•+ [2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid)] and DPPH (2,2-diphenyl-1-picrylhydrazyl), hydroxyl radical and hydrogen peroxide scavenging capacities, ferric reducing property and in vivo antioxidant capacity using Saccharomyces cerevisiae were observed in case of freeze-dried water extract of fermented wheat as compared to unfermented sample. Hence, SSF could be a promising technology to enhance the production and extraction of phenolic compounds for the design of different functional foods and for the specific use as nutraceuticals.