Use of Bacteria that Produce Linamarase in Cassava Processing for Gari

Abstract

Assessment of the effectiveness of microorganisms involved in gari fermentation in the degradation of cyanogenic glucosides was studied. Alcaligenes faecalis, Lactobacillus plantarum, Bacillus subtilis and Leuconostoc cremoris were isolated from cassava waste water while standard analytical methods were used to monitor the fermentation for total cyanogens. The linamarase activity observed for the isolates ranged from 0.0416 ìmol/ml/nmol (Lactobacillus plantarum) to 0.2618 ìmol/ml/nmol (Leuconostoc cremoris). Bacillus subtilis did not express any activity for the enzyme. Values obtained for total cyanogenic glucosides differed significantly at 24 h and 48 h (p<0.05) while at 96 h the values did not differ significantly (p>0.05). At 24 h, the cyanohydrins did not differ among the fermenting organisms. However, the mixed culture had the least amounts from 48 h to 96 h. Free cyanide produced by each organism did not differ at 24 h and 48 h but visible differences were observed at 72 h and 96 h. B. subtilis had the highest amount at 96 h (38 mg HCN/
kg) while the mixed culture had the least amount (26 mg HCN/kg). There was no significant difference in the rate of degradation of the linamarin by the microorganisms. pH decreased with increase in time of fermentation with the mash fermented by the mixed culture having the lowest pH of 4.19 at the end of fermentation. Titrable acidity increased with increase in fermentation time with the highest value of 1.05% at 96 h of fermentation produced by the mixed culture of microorganisms. These results show that although these isolates produced linamarase, their activities did not significantly affect the breakdown of the cyanogens.