UTILIZATION OF AGROINDUSTRIAL BY-PRODUCTS AS SUBSTRATE IN ENDOGLUCANASE PRODUCTION BY Streptomyces diastaticus PA-01 UNDER SUBMERGED FERMENTATION

Thermo-neutrophilic cellulases and chitinases characterized from a novel putative antifungal biocontrol agent: Bacillus subtilis TD11

Cellulose and chitin are the most abundant naturally occurring biopolymers synthesized in plants and animals and are used for synthesis of different organic compounds and acids in the industry. Therefore, cellulases and chitinases are important for their multiple uses in industry and biotechnology. Moreover, chitinases have a role in the biological control of phytopathogens. A bacterial strain Bacillus subtilis TD11 was previously isolated and characterized as a putative biocontrol agent owing to its significant antifungal potential. In this study, cellulase and chitinase produced by the strain B. subtilis TD11 were purified and characterized. The activity of the cellulases and chitinases were optimized at different pH (2 to 10) and temperatures (20 to 90°C). The substrate specificity of cellulases was evaluated using different substances including carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), and crystalline substrates. The cellulase produced by B. subtilis TD11 had a molecular mass of 45 kDa while that of chitinase was 55 kDa. The optimal activities of the enzymes were found at neutral pH (6.0 to 7.0). The optimum temperature for the purified cellulases was in the range of 50 to 70°C while, purified chitinases were optimally active at 50°C. The highest substrate specificity of the purified cellulase was found for CMC (100%) followed by HEC (>50% activity) while no hydrolysis was observed against the crystalline substrates. Moreover, it was observed that the purified chitinase was inhibitory against the fungi containing chitin in their hyphal walls i.e., Rhizoctonia, Colletotrichum, Aspergillus and Fusarium having a dose-effect relationship.

Solid-State Yeast Fermented Wheat and Oat Bran as A Route for Delivery of Antioxidants

The purpose of our study was to evaluate the potential of solid-state yeast fermentation (SSYF) in improving the phenolic acid content and composition, and the antioxidant activity of commercial wheat bran (WB) and oat bran (OB). The ultrasound-assisted methanolic extracts were compared for their total phenolic content (TPC), phenolics composition, and in vitro antioxidant activity in order to study the effect of fermentation time on the chemical profile and activity of bioactive compounds. The comparative analysis revealed significant differences (p < 0.05) between days of fermentation (0 through 6). The highest TPCs were obtained on day 3 for WB (0.84 ± 0.05 mg of gallic acid equivalents [GAE]/g dry weight [DW]), and on day 4 for OB (0.45 ± 0.02 mg GAE/g DW). The highest relative percentage increase in the phenolics concentration of WB was also registered on day 3 (ferulic acid +56.6%, vanillic acid +259.3%, dihydroxybenzoic acids +161.2%, apigenin-glucoside +15.3%); for OB, this was observed on day 4 (avenanthramide 2f +48.5%, ferulic acid +21.2%). Enhanced antioxidant activities were significantly correlated with the highest TPCs. Our results suggest that SSYF may be a useful procedure for enrichment of antioxidants in cereal bran, considering the design of different functional foods and nutraceuticals.

Optimization of Cellulase and Xylanase Productions by Streptomyces thermocoprophilus Strain TC13W Using Oil Palm Empty Fruit Bunch and Tuna Condensate as Substrates

The modified medium composed of the alkaline-pretreated oil palm empty fruit bunch (APEFB) and tuna condensate powder was used for cellulase and xylanase productions by Streptomyces thermocoprophilus strain TC13W. The APEFB contained 74.46% (w/w) cellulose, 15.72% (w/w) hemicellulose, and 6.40% (w/w) lignin. The tuna condensate powder contained 55.49% (w/w) protein and 11.05% (w/w) salt. In the modified medium with only 6.75 g/l tuna condensate powder, 10 g/l APEFB, and 0.5 g/l Tween 80, S. thermocoprophilus strain TC13W produced cellulase 4.9 U/ml and xylanase 9.0 U/ml. The enzyme productions in the modified medium were lower than cellulase (6.0 U/ml) and xylanase (12.0 U/ml) productions in the complex medium (CaCl₂ 0.1, MgSO₄·7H₂O 0.1, KH₂PO₄ 0.5, K₂HPO₄ 1.0, NaCl 0.2, yeast extract 5.0, NH₄NO₃ 1.0, Tween 80 0.5). When tuna condensate powder in the modified medium was reduced to 5.0 g/l and Tween 80 was increased to 1.5 g/l, S. thermocoprophilus strain TC13W produced cellulase and xylanase activities of 9.1 and 12.1 U/ml, respectively. This study shows that the cost of enzyme production could be reduced by using pretreated EFB and tuna condensate as a carbon and a nitrogen source, respectively.