Paenibacillus sp. strain HC1 xylanases responsible for degradation of rice bran hemicellulose

Design and application of an efficient cellulose-degrading microbial consortium and carboxymethyl cellulase production optimization

Microbial consortia with high cellulase activities can speed up the composting of agricultural wastes with high cellulose contents and promote the beneficial utilization of agricultural wastes. In this paper, rabbit feces and sesame oil cake were used as feedstocks for compost production. Cellulose-degrading microbial strains were isolated from compost samples taken at the different composting stages and screened via Congo red staining and filter paper degradation test. Seven strains, Trichoderma reesei, Escherichia fergusonii, Proteus vulgaris, Aspergillus glaucus, Bacillus mycoides, Corynebacterium glutamicum, and Serratia marcescens, with high activities of carboxymethyl cellulase (CMCase), filter paper cellulase (FPase), and β-glucosidase (β-Gase) were identified and selected for consortium design. Six microbial consortia were designed with these strains. Compared with the other five consortia, consortium VI composed of all seven strains displayed the highest cellulase activities, 141.89, 104.56, and 131.18 U/ml of CMCase, FPase, and β-Gase, respectively. The single factor approach and response surface method were employed to optimize CMCase production of consortium VI. The optimized conditions were: culture time 4.25 days, culture temperature 35.5°C, pH 6.6, and inoculum volume 5% (v/v). Under these optimized conditions, the CMCase activity of consortium VI was up to 170.83 U/ml. Fermentation experiment of rabbit feces was carried out by using the consortium VI cultured under the optimal conditions. It was found that the application effect was better than other treatments, and the fermentation efficiency and nutrient content of the pile were significantly improved. This study provides a basis for the design of microbial consortia for the composting of agricultural wastes with high cellulose contents and provides a support for beneficial utilization of agricultural wastes.

Effects of integrated biocontrol on bacterial wilt and rhizosphere bacterial community of tobacco

Bacterial wilt as a soil-borne disease was caused by Ralstonia solanacearum, and seriously damages the growth of tobacco. Integrated biocontrol method was explored to control bacterial wilt. Nevertheless, the long-term effects of the integrated biocontrol method on soil bacterial community, soil physicochemical properties and the incidence of bacterial wilt are not well understood. In this study, B. amyoliquefaciens ZM9, calcium cyanamide and rice bran were applied to tobacco fields in different ways. The disease index and incidence of tobacco bacterial wilt (TBW), soil physicochemical properties, colonization ability of B. amyoliquefaciens ZM9, and rhizopshere bacterial community were investigated. The results showed that the integrated application of B. amyoliquefaciens ZM9, rice bran and calcium cyanamide had the highest control efficiency of TBW and bacteria community diversity. Additionally, the integrated biocontrol method could improve the colonization ability of B. amyoliquefaciens ZM9. Furthermore, the integrated biocontrol method could effectively suppress TBW by regulating soil physicochemical properties, promoting beneficial bacteria and antagonistic bacteria of rhizopshere soil. This strategy has prospect of overcoming the defects in application of a single antagonistic bacteria and provides new insights to understand how to improve the colonization capacity of antagonistic bacteria and control efficacy for TBW.

Nutritional and Organoleptic Evaluation of Baked Products Incorporating Stabilized Rice Bran

Background:

Rice bran, a byproduct of rice milling is a rich source of fiber, proteins, fats and micronutrients. There is an increasing demand for functional foods that can provide a variety of nutrients besides providing bioactives rendering therapeutic value thereby reducing the risk of chronic diseases.

Methods:

The study was carried out to evaluate the physicochemical and in vitro antioxidative potential of stabilized rice bran powder [full-fat rice bran (FFRB) and defatted rice bran (DFRB)] in baked products. Three variants of each product viz. rusks and twisted sticks were prepared by incorporating FFRB and DFRB at 5%, 10% and 15% level along with the standard (control) without the addition of rice bran powder.

Results:

The results indicated that DFRB showed higher antioxidative potential and improved water absorption capacity (WAC), oil absorption capacity (OAC) than FFRB. Proximate analysis revealed that the protein and ash content of the baked products improved significantly (p ≤ 0.05) with an increased level of incorporation of FFRB and DFRB as compared to control. The DPPH activity of DFRB (78.7 ± 0.46) was significantly higher than FFRB (35.5 ± 2.89). Sensory appraisal of the rusk revealed that variant I and II with 5% and 10% level of incorporation were more acceptable as compared to control. The sensory appraisal of twisted sticks revealed that all the three variants were equally acceptable as the control sample.

Conclusion:

The incorporation of full fat and defatted rice bran powders to baked products enhanced their nutritional profile and physicochemical characteristics without affecting the organoleptic properties.

Functional and physiological properties of total, soluble, and insoluble dietary fibres derived from defatted rice bran

Enzymatic- gravimetric method was used to obtain three fractions of dietary from defatted rice bran. The functional and physiological properties such as viscosity, cation exchange capacity (CEC), and glucose dialysis retardation index (GDRI), cholesterol and bile salt adsorption capacity of the resultant fractions were evaluated. Insoluble dietary fibre (IDF) and soluble dietary fibre (SDF) when compared showed that SDF exhibited significantly (p < 0.05) higher viscosity (2.35 mPa.s), greater GDRI value (17.65 %) at 60 min and significantly lowered concentration of cholesterol at pH 7 (29.90 %, p < 0.05). However IDF showed the highest CEC and its adsorption capacity of bile salt was higher than SDF (18.20 % vs. 13.76 %; p < 0.05), while CEC and cholesterol absorption capacity of TDF were similar to SDF. These properties indicate that rice bran soluble, insoluble and total fibres are functional ingredients which can be added to various food products and dietetic, low-calorie high-fiber foods to enhance their nutraceutical properties and health benefits.