The cultural conditions for the production of enhanced formation of L-serine (up to 7 g/L) are described with the methylotrophic bacterium Pseudomonas 3 ab (DSM 672). The batch process is divided into three parts: (1) the biomass production phase, (2) substrate limitation period, and (3) L-serine accumulation phase. The initial specific production rate of qp = 0.1 g L-serine/g dry wt/h is based on the inhibition of the L-serine pathway. This is accomplished by high precursor concentrations (glycine) and a pH shift to pH 8.5. The enzymatic background is discussed. Furthermore, a coupling of the L-serine process with a L-tryptophan-producing process is demonstrated.