ABSTRACT

The enzymatic potentials of microorganisms isolated from retting cassava were evaluated for the purpose of pectinase, cellulase and amylase activities. Cassava tubers of l2months old were collected from 3 different sources: 5 from Ahieke, 5 from Ndoru and 5 from Umuariga, they were handpeeled, cut into cylinders, washed, submerged into water and allowed to ret. After retting a dilution of the retted tubers were inoculated into different media plates: De-Man Rogosa Sharp agar, Sabouraud Dextrose agar, Nutrient agar, Mannitol salt agar and MacConkey agar and incubated at 30°C for 3-5 days. A total of 35 isolates was identified in the retting cassava samples which are bacteria 25(71.43%) and fungi 10(28.57%). The bacteria isolates identified include Bacillus subtilis, Escherichia co/i, Staphylococcus aureus, Lactobacillus spp and Proteus spp. While the 2 fungal isolates and lyeast was identified which include Aspergillus niger, Rhodotorula spp and Saccharoinyces cerevisiae respectively. The total viable count of the isolates in heterotrophic plate count, fungal plate count and lactic acid bacteria plate count were increasing as the retting hours increases from 1.94x106cfu1m1 to 2.52xl06cfulml, 1. 823x I 06cfu/ml to 2. 808x 106cfu/ml and 1.712x 106cfu/ml to 2.897x106cfu/ml respectively while coliform plate count and Staphylococcus plate count were decreasing from 2.014x106cfu/ml to 7.47x10cfu/ml and 2.l3lxl06cfu/ml to 7.76x105cfu/ml respectively. The distribution of the isolates shows that Bacillus sublilis, Escherichia co/i, Staphylococcus aureus and Proteus spp dominated the beginning of the fermentation period while Lactobacillus spp, Saccharomyces cerevisiae and Aspergillus niger dominated the later stage of fermentation. Bacillus subtilis has the highest percentage occurrence 8(22.9%) while Rhodotorula spp has the lowest percentage occurrence 2(5.7%). The production of amylase enzyme was recorded with all the isolates with the exception of Staphylococcus aureus that produced none of the enzymes. Some of the isolates were able to produce cellulase enzyme while some produce pectinase enzyme. Proteus spp neither produced cellulase nor pectinase. Antimicrobial susceptibility pattern of the bacteria isolates shows that Rifampicin and Gentamycin have a high level of sensitivity to all the isolates with 4(16.0%) and 5(20.0%) while chloramphenicol, Norfioxacin and amoxil have a high resistance to the isolates with 3(33.0%), 2(22.0%) and 2(22.0%) respectively. Results from this study shows that enzymes like amylase, pectinase and cellulase from microorganisms played an important role in retting of cassava tubers.