Study on mcl-PHA Production by Novel Thermotolerant Gram-Positive Isolate

摘要

The novel isolated thermotolerant bacteriaBacillus thermoamylovoransstrain PHA005 was obtained from palm oil mill effluent. This strain showed an ability to produce medium-chain-length polyhydroxyalkanoates (mcl-PHAs) at 50.77% of dry cell weight (DCW) using sodium octanoate. Therefore, the production of mcl-PHA was enhanced by optimising the effects of nutrients and environmental conditions. The optimal conditions were 3.0 g/L sodium octanoate, a carbon to nitrogen ratio of 5:1 (0.02 g/L ammonium chloride), 45 degrees C incubation, initial pH 7.0 and agitation speed at 150 rpm. Under optimal conditions, the maximum mcl-PHA accumulation increased from 50.77% to 63.27% of DCW and 2.75 +/- 0.03 g/L cell growth, 1.74 +/- 0.02 g/L mcl-PHA concentration was achieved after 120 h cultivation. The composition of mcl-PHA contained C8-C18 while 3-hydroxyhexadecanoic (3HHD) was found at the highest composition (39.25 mol%) which has not been previously reported.