Screening and characterization of potential cyanide tolerating lactic acid bacteria from cassava pulp juice

Abstract

Lactic acid bacteria are predominant microorganisms that play important roles during cassava fermentation. Most efforts to develop cyanide tolerant isolates for cassava fermented products have been unsuccessful because of cyanide toxicity in cassava tubers. The objectives of this study were identifying cyanide tolerating bacteria and study their tolerability efficiency. 119 lactic acid bacteria were isolated from fermented cassava pulp juice. Out of the total isolated bacteria, ten potential cyanide tolerating bacteria was screened. The cyanide tolerance efficiency was studied at 100, 400, 600 and 8000mg/L potassium cyanide, growth at different temperature and pH were analyzed. The maximum growth rate reading of the screened isolates ranges (0.674 to 1.116) at 600nm in maximum cyanide concentration. Isolate CD1, LA2, LA1 and CD2 showed maximum cyanide tolerance of (74.4, 72.66, 70.66 and 68.73%) respectively at 800mg/l after 48hr of incubation. The cyanide tolerability potential of individual isolates varies across different cyanide concentration. Above all 10 isolates were resistant to maximum cyanide concentration and possess potential of cyanide tolerating properties that help their selection and application in a controlled process to detoxify cassava roots for food and feed utilization. There was a general decrement in all samples over 48 h fermentation periods from 6.00 to 3.18 and the bacterial isolates showed significant growth at room temperature which were between ʺ25°Cʺ and ʺ40°Cʺ.