Optimisation of glutamic acid production from cassava starch factory residues using Brevibacterium divaricatum

There is serious concern about the disposal of solid residues left after large-scale cassava starch extraction. Storage of residues if badly managed, leads to serious environmental problems. Owing to the high starch content and organic nature of these wastes, an attempt has been made to utilise it for the production of glutamic acid, the precursor of monosodium glutamate, employing submerged fermentation using Brevibacterium divaricatum. The effect of temperature, pH, inoculum size, speed of agitation and nitrogen sources were studied. With 0.7% ammonium nitrate in the medium, highest glutamate yield of 3.86% based on the weight of the residues was obtained at 30 °C at a pH of 7.0. The highest glutamate production was recorded at 5% inoculum size at an agitation speed of 180 rpm. The study showed that the solid residues from cassava starch factories could serve as a low-cost substrate for glutamic acid production.