Evidence of a positive effect of hydrolysis rate of fish peptones on Escherichia coli culture kinetics.

Abstract

International audienceThe aim of this work was to evaluate the potential use of a fish hydrolysate as microbial substrate, and the effect of an increased (acidic) hydrolysis rate on the cell yield. With this objective, we compared E. coli growth kinetics on fish hydrolysates and on casein hydrolysates as a reference. We measured lag-phase durations, growth rates in exponential phase, and maximum cell densities. On casein hydrolysates, the lag phase was shorter, and the growth rate and maximum cell density were higher as compared to that on fish protein hydrolysates. For both substrates, when the concentration in the medium was increased five times, the maximum cell density was also increased approximately five times, showing that the quality, or the concentration, of these nitrogen sources were the limiting factors in our conditions. Following hot hydrochloric acid hydrolysis of both enzymatic hydrolysates, both substrates showed an approximately 170% increase of the maximum cell density compared to the untreated ones. These results suggest that the rate of hydrolysis of proteins dramatically affects the final cell density in cultures. Therefore, at least for our E. coli strain, the quality of the protein hydrolysate seems to be highly related to the hydrolysis rate