纳豆芽孢杆菌固态发酵小米糠产抗氧化肽工艺优化

为提高小米糠蛋白资源的利用率,为小米糠的深加工提供参考,采用纳豆芽孢杆菌对小米糠进行固态发酵以获得小米糠抗氧化肽。在单因素试验的基础上以小米糠发酵后水提液的总抗氧化能力(total antioxidant capacity,T-AOC)为指标,使用Plackett-Burman试验对发酵条件进行筛选,然后使用响应面法对发酵条件进行优化,并测定优化后小米糠水提液的多肽含量和1,1-二苯基-2-三硝基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)自由基清除能力。结果显示最适发酵条件为:小米糠平均粒径0.22 mm(60~80目)、菌液接种量0.4 mL(约108 CFU/mL)、初始pH 6.7、发酵时间26 h、发酵温度35℃。此条件下小米糠固态发酵后提取液的T-AOC实际值为(344.51±8.02)U/g小米糠,多肽提取量为(68.37±0.92)mg/g小米糠,清除DPPH自由基IC50为0.12 mg/mL。该研究表明,小米糠固态发酵条件经过优化后能够获得具有较高抗氧化能力的生物活性肽。

Optimization of Solid State Fermentation Conditions for Production of Antioxidant Peptides from Millet Bran by Bacillus natto

In order to improve the utilization rate of millet bran as a protein source and to provide references for the intensive processing of millet bran, solid state fermentation of millet bran by Bacillus natto was optimized for increased production of antioxidant peptides. Firstly, one-factor-at-a-time experiments were carried out. Secondly, the fermentation conditions with a significant effect on the total antioxidant capacity (T-AOC) of aqueous extracts from fermented millet bran were selected using Plackett-Burman design for further optimization using response surface methodology (RSM). The polypeptide content and 1,1-diphenyl-2-trinitrobenzene hydrazine (DPPH) radical scavenging ability of the aqueous extract from millet bran fermented under optimized conditions were determined. Results showed that the optimum fermentation conditions were as follows: average particle diameter of millet bran, 0.22 mm (between 60 and 80 mesh); inoculum size, 0.4 mL; initial pH, 6.7; fermentation time, 26 h; and fermentation temperature, 35 ℃. Experiments conducted under these conditions yielded an extract with a T-AOC of (344.51 ± 8.02) U/g, and a polypeptide yield of (68.37 ± 0.92) mg/g millet bran. The results also showed that the bioactive peptides had strong DPPH free radical scavenging activity with an IC50 value of 0.12 mg/mL. Therefore, this study proves that bioactive peptides obtained from fermented millet bran have a high antioxidant capacity.