Physiology and kinetics of trimethylamine conversion by two methylotrophicstrains in continuous cultivation systems

The change of dilution rate (D) on both Methylophilus methylotrophus NCIMB1 1348 and Methylobacterium sp. RXM CCMI908 growing in trimethylamine (TMA) c hemostat cultures was studied in order to assess their ability to remove od ours in fish processing plants. M. methylotrophus NCIMB11348 was grown at d ilution rates of 0.012-0.084 h(-1) and the biomass level slightly increased up to values of D around 0.07 h(-1). The maximum cell production rate was obtained at 0.07 h(-1) corresponding to a maximum conversion of carbon into cell mass (35%). The highest rate of TMA consumption was 3.04 mM h(-1) occ urring at D=0.076 h(-1). Methylobacterium sp. RXM CCMI908 was grown under s imilar conditions. The biomass increased in a more steep manner up to value s of D around 0.06 h(-1) The maximum cell production rate (0.058 g l(-1)h(- 1)) was obtained in the region close to 0.06 h(-1) where a maximum conversi on of the carbon into cell mass (40%) was observed. The maximum TMA consump tion was 2.33 mM h(-1) at D = 0.075 h(-1) The flux of carbon from TMA towar ds cell synthesis and carbon dioxide in both strains indicates that the cel l is not excreting products but directing most of the carbon source to grow th. Carbon recovery levels of approximately 100% show that the cultures are carbon-limited. Values for theoretical maximum yields and maintenance coef ficients are presented along with a kinetic assessment based on the determi nation of the substrate saturation constant and maximum growth rate for eac h organism.