ISSN:
1573-0972
Keywords:
Growth and production coupling
;
lactic acid bacteria
;
yeast extract
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Process Engineering, Biotechnology, Nutrition Technology
Notes:
Abstract Lactobacillus helveticus was cultivated batchwise on whey permeate supplemented with 2–30g yeast extract l-1. For low supplementation levels, growth was slow, and a long maintenance phase in the absence of any cell autolysis was observed. When the yeast extract concentration was increased, growth time increased slightly; under these circumstances, a large increase of maximum biomass concentration was recorded, indicating a clear nitrogen source starvation at low supplement concentration. At the same time the length of the maintenance phase decreased; for a 30gl-1 supplementation, it vanished and a death phase was observed instead: this behaviour highlighted a shift from nitrogen to carbon source starvation. For more and more supplemented media, the final lactic acid concentration was constant, while fermentation time decreased significantly; a growth-associated production phase was followed by a maintenance production phase. The part played by the former mecha nism was under tight control of yeast extract concentration: for 30gl-1 supplementation, 83% of total lactic acid was provided by a growth-linked production process.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1023/A:1008828415639
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