Methanol metabolism in Paracoccus denitrificans I. Isolation and characterization of mutants with defects in methanol utilization

Abstract

Bacillus licheniformis is a facultative aerobic bacterium used in the fermentation industry for the production of enzymes. For a complete description of the production process knowledge of growth parameters, electron-chain composition and efficiency of energy conservation is obligatory. B. licheniformis S1684 is able to produce an alkaline serine protease exocellularly. In glucoselimited chemostat cultures the specific rate of protease production was maximal at a specific growth rate value (Ix) of 0.22. At higher growth rates protease production was repressed (catabolite repression). Dependent on Ix 10-20% of the glucose input was used for exocellular product formation. The degree of reduction of exocellular products (Tp) was 4.1, showing that products are not more reduced than biomass. Maximum molar growth yields were high and indicated a high efficiency of growth. The values of yg~auX and y ~ x were 83.8 and 53.3, respectively. When y~ax was corrected for the amount of glucose used for product formation a value of 100.3 could be calculated. These high maximum YATP. molar growth yields most probably are caused by a high max In anaerobic batch experiments a YATP of 14.6 could be determined. The efficiency of energy conservation most probably is low, which is indicated by the measured H +/O ratios of about 4 in cells taken at different Ix-values during glucose limitation, indicating that at the most one or two traditional sites of oxidative phosphorylation are active. The strain used appeared to be instable in protease production and cell morphology. Non-protease-producing cells most probably develop from producing cells by mutation in the rel-gene. Producing cells are relaxed (tel-) and non-producing cells stringent (rel § In non-protease-producing chemostat cultures y~ax was significantly higher because no glucose was needed for protease production.