Short-Chain Poly(γ-diaminobutanoic acid), A Poly(amino acid) Produced by a Marine Bacteria Bacillus pumilus

One marine bacteria Bacillus pumilus was isolated using allura red as ε-poly-L-lysine (ε-PL) secretion indicator. But actually the product was identified as poly-γ-L-diaminobutanoic acid (γ-PAB) by ionization-time-of-flight mass spectrometry, not coproduced with ε-PL. The polymerization degree of γ-PAB was 4-22, namely short-chain γ-PAB, compared with that in S. celluloflavus, and it exhibited stronger inhibitory activities against yeasts than long-chain γ-PAB but weaker activities against bacteria. The fermentative behavior of B. pumilus was investigated, and the γ-PAB production was 38.6 mg/L in shake flask and was enhanced to 284.2 mg/L in 5-L bioreactor by a pH control strategy. Interestingly, the suitable pH for B. pumilus to produce γ-PAB was 4.8, different from 4.0 for current Streptomyces strains, which suggests a potential new metabolic mechanism in B. pumilus as a novel γ-PAB producer. No studies on short-chain γ-PAB production in bacteria have been reported previously and we considered that this is a new discovery in the field of homopolymer research.