Optimization of Wickerhamomyces anomalus Fermentation Conditions for Pectinase Production Based on Wet Processing of Arabica Coffee in Yunnan Province

In order to improve the pectin-degrading efficiency in wet processing of Arabica coffee in Yunnan, Box-Behnken design and single factor experiment were used to optimize the fermentation conditions of five pectinolytic Wickerhamomyces anomalus strains from the fermentation broth of Arabica coffee in Baoshan, Yunnan during wet processing with pectase activity as an indicator. The results showed that the five strains all synthesized pectin lyase (PL), polygalacturonase (PG), and pectin methylesterase (PM). Among them, strain CAP5 had strong ability to produce PG and PL, while strain CAP4 secreted a large amount of PM. Under optimized conditions, the activity of PG, PL, and PM of the five strains came in at 250.17～411.20 U/mL, 12.98～16.55 U/mL, and 208.52～322.83 U/mL, respectively. The four factors of nitrogen source concentration, fermentation time, Mn2+ concentration, and pH value were optimized and the optimal pectinase-producing fermentation conditions for five strains were as follows: peptone 2.2 g/L, fermentation time 30 h, Mn2+ 1.5 mmol/L, and pH 4.3. After fermentation under the optimized conditions, the maximum PG activity of CAP5 amounted to 411.20 U/mL, 114.03％ higher than that before optimization. Meanwhile, the PG activity of strains CAP3, CAP4, CAP8, and CAP10 increased by 86.74％, 114.55％, 65.79％, and 66.07％, respectively, and the activity of PL and PM of the five strains rose 150.35％～218.56％ and 341.07％～418.52％, respectively. These findings suggested that W. anomalus strains could be used as coffee starter and had great potential for the lysis of pectin.