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Economical production of agricultural γ-polyglutamic acid using industrial wastes by Bacillus subtilis

Zhang, Chao, Wu, Daoji, Ren, Huixue
Biochemical engineering journal 2019 v.146 pp. 117-123
Bacillus subtilis, crystallization, experimental design, glutamic acid, industrial wastes, monosodium glutamate, pollution, pollution control, polyglutamic acid, poultry manure, regression analysis, response surface methodology, soybean cake
Industrial wastes, such as monosodium glutamate waste liquor, chicken manure and soybean cake, were used for agricultural γ-polyglutamic acid (γ-PGA) production by Bacillus subtilis ZC-5. Crude extract of glutamic acid after isoelectric crystallization (CEGA) could be used instead of glutamate for γ-PGA production. The optimal composition of medium was obtained by response surface methodology. Firstly, Plackett-Burman design was undertaken to assess the effects of eight factors. With statistic regression analysis, the significant factors affecting γ-PGA production were determined as follows: chicken manure, soybean cake and CEGA. Then the Box-Behnken design was adopted for further optimization. The optimal addition amounts of factors were determined as: 62.35 g chicken manure, 25.15 g soybean cake and 15.09 g CEGA. Under such condition, the γ-PGA yield was increased to 6.57 ± 0.13%, which was 20.6% higher than the maximum value of the single factor tests. These investigations would lay a foundation for reducing the pollution of industrial wastes, exploring a late-model for agricultural γ-PGA production.