The Effect of Discontinuous Methanol Addition on the Growth of a Carbon-limited Culture of Pseudomonas

Abstract

S U M M A R YAs the interval between methanol additions to methanol-limited cultures of Pseudomonas methylotropha was increased beyond 20 s the yield of bacterial dry wt/g of methanol fell significantly. Discontinuous methanol additions also caused cycling in the values of a number of parameters, including pH, dissolved oxygen tension, CO, production and amino acid pool concentration. It is suggested that after each addition of methanol a burst of growth occurred, followed by a period of starvation. These observations are discussed in the light of continuous culture practice and theory.

The Effect of Dropwise Addition of Medium on the Yield of Carbon-limited Cultures of Arthrobacter globiformis

“…Lowered yields of Artlmbactrr g1ohifomii.s at dilution rates below 0.1 h-l under carbon limitation thus cannot be attributed to the mode of substrate addition; the suggestion that the effect is caused by a maintenance energy requirement remains more plausible. Brooks & Meers (1973) have shown that growth can be affected by the discontinuous addition of substrate, so it would be wise to remember this in designing a continuous culture system, though their results do not have such wide-reaching implications as was initially thought. This is a paper of the Journal Series, New Jersey Agricultural Experiment Station, Cook College, Rutgers University, New Brunswick, New Jersey, U.S.A.…”

“…g Herbert, 1959Herbert, , 1961. This has usually been attributed to ii maintenance energy requirement, but Brooks & Meers ( 1973) suggested another possible cause.…”

“…g Herbert, 1959Herbert, , 1961. This has usually been attributed to ii maintenance energy requirement, but Brooks & Meers ( 1973) suggested another possible cause. In studying the effect of discontinuous addition of methanol to 'continuous' cultures of Pseudoriioiras, they found a decrease in yield as the time between additions was extended from 20 to loo s. They suggested that either methanol was 'wasted' during periods of excess which followed methanol addition, or, i n growing intermittently, organisms were using energy in continually adj~isting their physiology and consequently less substrate was available for incorporation into cell material.…”

Quasi-continuous fermentation in a reverse-flow diafiltration bioreactor

“…In these studies, it could be shown that overflow metabolites occur due to locally high substrate concentrations. Furthermore, short-term oxygen limitations of the microorganisms could be detected, causing a reduction of biomass and product concentration or the formation of overflow metabolites [14,20,23,25,26,28,30,31,33]. However, also positive effects of short-term oxygen limitation could be noticed as glucose is in excess and, thus, the number of dead cells decreased [14,26].…”

“…In contrast, cells are retained in their regions exist simultaneously within the same bioreactor. Studies investigating heterogeneities of nutrients by applying glucose pulse experiments or bioreactors with poor mixed regions were conducted with Saccharomyces cerevisiae [20][21][22][23], Escherichia coli [24][25][26][27] and other bacteria [28][29][30][31][32] and yeast. In these studies, it could be shown that overflow metabolites occur due to locally high substrate concentrations.…”