Secretion Of Methionine By Microorganisms Associated With Cassava Fermentation

Abstract

Forty-six (46) bacteria were isolated from different sites associated with garri
production from cassava: cassava pulp grated for garri production, grating machines,
soil in the vicinity of the production of garri, and utensils involved in the processing
of cassava into garri in several locations in Anambra State of Nigeria. Of these,
Lactobacillus plantarum, Lactobacillus sp., Leuconostoc sp., Corynebacterium sp.
and Bacillus sp. secreted methionine. The organisms were assessed for optimum
methionine production at various levels of glucose, ammonium sulphate and varying
mixtures of potassium hydrogen phosphate and di-potassium hydrogen phosphate. All
the organisms required 10 g glucose for maximum methionine secretion. All the
isolates required 20 g of (NH4)2SO4/litre, except for Bacillus sp. which required as
little as 5 g of (NH4)2SO4/litre. The organisms' requirement for phosphate varied
widely: the two lactobacilli required 0.5 g KH2PO4 and 1.5 g K2HPO4 per litre,
Leuconostoc sp. and Bacillus sp. required 1.0 g KH2PO4 and 3.0 g K2HPO4 per litre.
Lactobacillus spp. were the highest secreters of methionine, followed in that order by
Leuconostoc sp., Corynebacterium sp. and Bacillus sp. The optimum period of
incubation for the secretion varied from 48 h to 96 h, which is the period for cassava
mash fermentation in garri production. The findings on Lactobacillus plantarum,
Lactobacillus sp. and Leuconostoc sp. are of importance in any possible effort to
increase the methionine content of garri. In this study the maximum quantities of
methionine were secreted after 96 hours and 72 hours respectively by the lactobacilli
and Leuconostoc sp. Since lactic acid bacteria are micro-aerophilic, it is suggested
that lactic acid bacteria (the two lactobacilli and Leuconostoc sp.), which are the
major organisms involved in cassava fermentation for garri production, may, in the
less aerated environment of the cassava mash, produce more methionine and in
shorter time, than observed under the aerobic conditions of this work.

Keywords: garri, fermentation, lactic acid, methionine

AJFAND Vol. 8 (1) 2008 pp. 77-90