Optimal culture conditions and characterization of cellulolytic bacteria from cassava dumpsites in Ibadan, Nigeria

Abstract

This study is designed to investigate cellulolytic bacteria capable of removing cellulolytic wastes that are produced from cassava during processing. Cellulolytic bacteria isolates from cassava dumpsite soil in Ibadan, Nigeria were characterized and their optimal culture conditions determined. The total viable bacterial count of the sample of cassava dumpsite soil was 24.4 x 108cfu/g. A total of twenty four bacteria were isolated from the samples out of which nine of the bacterial isolates were positive for cellulose degrading abilities. The 16S rDNA analysis of two bacterial isolates which gave the highest zones of hydrolysis on carboxy-methyl cellulose agar plates showed maximum similarity ratio towards strains of Kurthia gibsonii (90%) and Myroides odoratimimus (98%) using BLAST and hence the isolates were referred to as Kurthia gibsonii CAC1 and
Myroides odoratimimus CAC2 respectively. Kurthia gibsonii CAC1 which was motile, aerobic, rod-shaped, nonpigmented and possessing a Gram positive reaction grew best at incubation temperature of 30oC, pH 5.5 and
on lactose and ammonium chloride supplemented medium. Also, at incubation temperature of 30°C there was enhanced growth of a light yellowish, non-motile, aerobic, and rod-shaped Gram negative M.  odoratimimus CAC2 at pH 6.0. Lactose and urea were best carbon and  nitrogen sources respectively in the growth medium boosting the bacterial proliferation. It can be concluded that these microorganisms if properly cultivated can be used to reduce cassava waste littering in the environment.

Key Words: Cassava, cellulolytic, carboxy-methyl cellulose, Kurthia gibsonii, Myroides odoratimimus.