EFFECT OF TEMPERATURE AND PRESSURE ON GROWTH AND METHANE UTILIZATION BY SEVERAL METHANOTROPHIC CULTURES

Several methanotrophic microorganisms, i.e., Methylococcus capsulatus (Bath), Methylomonas albus (BG-8), Methylosinus trichosporium OB3b, an d Methylocystis parvus (OBBP), were evaluated for growth and methane u tilization. The effect of temperature was examined in the range of 25 to 45 degrees C for growth and methane utilization. The temperature va riations (25-35 degrees C) had minimal effect on growth of M. albus an d M. parvus. Methane consumption varied at different temperatures with a maximum of 0.67 mol%/h and 0.53 mol%/h. at 30 and 35 degrees C, res pectively, for M. albus and M, parvus. The growth and methane consumpt ion was slower for M, trichosporium OB3b as a maximum methane consumpt ion of 0.07 mol%/h was obtained at 25 degrees C and growth was inhibit ed at 35 degrees C. M. capsulatus grew the best at 37 degrees C and gr owth was affected at higher temperature of 45 degrees C. Of the differ ent cultures examined, M, albus and M, capsulatus grew the best and we re further evaluated for the effect of pressure in the range of 10-50 psi. The results obtained using M. albus demonstrated an enhancement i n methane consumption rate by fourfold and final cell concentration by 40% at a pressure of 20 psi by injecting a methane/oxygen mixture, ho wever further increase in the pressure up to 50 psi inhibited the grow th. The inhibition was not seen with nitrogen incorporated mixture of oxygen and methane, which suggest that the high partial pressure of me thane and/or oxygen are inhibitory for the growth of M. albus. M. caps ulatus was more sensitive to pressure as evidenced by inhibition at th e relatively low pressure of 10 psi.