Fermentation of amylolytic yeast and lactic acid bacteria to improve the quality of modified cassava

Abstract

The amylolytic activity has been studied in yeast and lactic acid bacteria (LAB) which are isolated from various types of traditional fermented cassava. The study aimed to obtain yeast and LAB isolates which high amylolytic activity for inoculum in cassava fermentation. A total of 23 yeasts and 22 LAB isolates were isolated from Gatot, Tiwul, Tapai, and Cassava fermented using chloramphenicol yeast glucose (CYG) media for yeast and de Man Rogosa Sharpe agar (MRSA) + CaCO3 for LAB. Yeast amylolytic activity was tested using yeast extract peptone starch agar medium, while the amylolytic LAB used MRS + starch media with Lugol’s iodine indicator. Colonies showing clear zone areas were measured as amylase activity on the iodine complex method. Isolates that have the highest amylolytic activity were used as inoculum in cassava fermentation. Yeast Tr7 and LAB G6 isolates showed the highest amylolytic activity (0.0624 U/mL and 0.0627 U/mL). Cassava fermentation products using yeast Tr7 and BAL G6 resulted 52.06% of hydrogen cyanide (HCN) reduction higher than without inoculum (32.32%). According to biochemical identification using API 50 CHL kit, LAB G6 isolate was 99.6% identical with Pediococcys pentosaceus whereas biochemical identification using API 20 C AUX showed that yeast Tr7 was 95.8% identical with Candida tropicalis. The biochemical identification result was similar to the molecular identification result. In molecular identification using 28S rRNA sequence analysis revealed that yeast Tr7 was 99% similar with Candida tropicalis NITCSK13 strain. LAB G6 was 100% similar with Pediococcus pentosaceus BSS1375 strain using 16S rRNA sequence analysis. C. tropicalis Tr7 and P. pentosaceus G6 potentially used for inoculum in cassava fermentation process to improve cassava quality as a functional food.