Serine dehydratase from bacteria

Survival of Brevibacterium linens during nutrient starvation and intracellular changes

The present work reports the survival capacity of a strain of Brevibacterium linens isolated from a French camembert cheese and the ensuing changes in cell composition. Exponentially growing cells were harvested, washed and resuspended with shaking in pH 8.0 buffer at 21 degrees C in the absence of a carbon source. The viability of this strain, assessed with slide cultures, is much less than that of coryneform bacteria isolated from soil samples, even though no cell lysis was detected. Intracellular RNA was rapidly consumed during the first few days although magnesium levels remained high. The quantity of DNA initially increased by 17% within 24 h and then remained stable during the 30 days of the experiment. During the same period, absorbance of the medium at 260 nm reached 2 absorbance units. Reserve polysaccharides in this strain are less abundant than in Arthrobacter and were rapidly consumed. Proteolysis was regular and thus maintained a pool of free amino acids which was greater than 60% of the initial value. There was a parallel accumulation of ammonia in the medium. Catalase activity decreased regularly during the first 80 h whereas the quantity of Adenosine-5'-triphosphate (ATP) dropped by 47% in 10 h, stabilizing at less than 10% of its initial value. Cell respiration declined very rapidly and was very low after 24 h.

Profiles for pH, temperature, and dissolved O2 levels in enzyme production: monitoring in small-scale fermentors

The profiles thus established may be utilized for investigations of an organism's relationship to its microenvironment including metabolic shifts and pathways. Areas of maximum respiratory activity, enzyme production, enzyme degradation, and attainment of the stationary phase are quite evident; however, duration and magnitude of the various phenomena may change with nutrient, temperature, and aeration efficiency. Practical application of this simplified method would include: a) determination of environmental conditions existing during maximum growth or enzyme synthesis and application of these conditions to feedback control; b) estimation of requirements for pH, oxygen, and heat removal capacities needed for scale-up; c) specific points during the fermentation at which samples should be analyzed to yield maximum information on depletion of nutrients and its effects on microbial activity.