Study on the microbial symbiosis of Candida Boidinii and Bacillus Subtilis for improvement of solube solid content extraction of Robusta coffee by fermentation

Abstract

A combination of C. boidinii and B. subtilis is used as a system to evaluate the microbial symbiosis between yeast and bacteria in coffee fermentation and to study cellulase and pectinase production in this system. The objective of this thesis is find out optimum factors to produce cellulase and pectinase by this microbial symbiosis under submerged fermentation. In addition, their application in improving soluble solid content extraction of coffee was obtained. The results showed that in the microbial symbiosis of C. boidinii and B. subtilis, the best achievement of cellulase production was 21.72 U/ml after adjusting optimal conditions including total soluble solid content in mollases at Brix 100, pH at 4.5 with 30% of CMC 2% and the ratio of living cells between C. boidinii and B. subtilis is 3:1. In contrast, pectinase production was achieved activity of 63.83 U/ml with total soluble solid content in mollases at Brix 100, pH at 4.5, 50% of pectin 2% and the ratio of living cells between C. boidinii and B. subtilis is 1:3. In addition, the soluble solids content was increased more 40% than the control culture with the ratio in the number of living cells is 1:1 (C. boidinii: B. subtilis) after 30 hrs. These result showed that a combination of C. boidinii and B. subtilis has positive effects on enzyme production and soluble solid content extraction of coffee, which can be applied for producing a high quality – low cost coffee product in food industry. Keywords: B. subtilis, C. boidinii, cellulase, pectinase, soluble solid content