Production of L-Lysine and Some Other Amino Acids by Mutants of B. methanolicus

Abstract

Bacillus methanolicus is is a Gram-positive, endosporeforming, facultative methylotroph with an optimal growth temperature of 50-53 º C. This bacterium employs the efficient ribulose-monophosphate pathway for formaldehyde assimilation and possesses a novel nicotinamide adenine nucleotide-dependent methanol dehydrogenase (Dijkhuisen et al, 1988) rather than the cytochrome linked MDH found in gram-negative methylotrophs. Several isolates similar to those isolated by us (Schendel et al, 1990) have been described and have been shown to be related to Bacillus frimus and B. azotoformans (Arfman, Dijhuizen, 1993). We have previously shown that mutants of B. methanolicus strains MGA3 and NOA2 which lacked homoserine dehydrogenase (methionine, threonine auxotrophs) and were also resistant to the lysine analogue, S-(2-aminoethyl)-L-cysteine (AEC) produced significant amounts of lysine when grown in a mineral salts medium under threonine limited conditions in fed-batch fermentations (Schendel et al, 1990).