Production of Citric Acid from Apple Pomace Enzymolyzed by Cellulase

Cellulase can evidently increase the content of glucose and has a significant effect on the production of citric acid from apple pomace by Aspergillus niger. Based on experiments, a cellulolytic enzyme named cellulase A6 was found able to produce about 170 g glucose from 1 kg dried apple pomace after 12 h reaction, with cellulase concentration of 20 U/g in the medium at 50oC, natural pH without pretreatment of alkali. Using the treated apple pomace as a liquid state substrate, Aspergillus niger-C selected out was able to produce about 256 g citric acid from 1 kg dried apple pomace at 35oC in 3 d or 30oC in 5 d with flask rotation speed of 210 r/min, and the conversion of citric acid could reach 80% based on the amount of sugar consumed.