Synthesis of L-asparaginase by Serratia marcescens (Nima).

The production of L-asparaginase by two mutants of Serratia marcescens grown on 14 different media was studied. The enzyme content increased from trace levels to 2·4 international units per ml when the organisms were grown in glycerol-peptone yeast extract medium. Glucose was the best carbon source under aerobic conditions. The enzyme content increased when L-asparagine was present in the growth medium.

An actinomycete producing L-3,4-dihydroxyphenylalanine from L-tyrosine.

An actinomycete was isolated during a soil screening programme to obtain L-3,4-dihydroxyphenylalanine producers. A mutant of this organism was isolated by chemical mutagenesis and it accumulated 1 g/litre L-dihydroxyphenylalanine when grown on L-tyrosine. Resting cells converted 30% of tyrosine in the reaction mixture. The use of resting cells for dihydroxyphenylalanine production is advantageous as it eliminates interfering substances which accumulate during fermentation.