Optimization of preparation of polysaccharide feed additive by solid fermentation of Radix isatidis residue by Bacillus subtilis
In order to utilize Radix isatidis residue in high value,the solid fermentation process from Radix isatidis residue to produce polysaccharide feed additive was optimized,and its antioxidant capacity was studied.The results showed that the high-yielding cellulase strain Bacillus subtilis YBS-18 was isolated from 28 strains.The production process of polysaccharide from solid fermentation of Bacillus subtilis YBS-18 isatis root residue was optimized by single factor test and response surface.The optimal process was determined as follows:The liquid-solid ratio was 1.2 mL/g,the loading rate was 0.3 g/mL,the glucose concentration was 8％,the ammonium sulfate concentration was 4.5％,the inoculation rate was 4.5％,and the fermentation temperature was 38 ℃.Under the optimum fermentation conditions,the polysaccharide content reached 28.17 mg/g.The polysaccharide showed good scavenging ability for DPPH free radicals,hydroxyl free radicals and superoxide anion free radicals,and the scavenging rate increased with the increase of polysaccharide concentration.The results show that the process improved the nutritional value of Radix isatidis residue and provided a theoretical basis for the development and application of feed additives of Radix isatidis residue.
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