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Title: Effect of malic acid on the growth kinetics of Lactobacillus plantarum

Author
item PASSOS, FREDERICO - UNIV FED DE VICOSA, BRAZ.
item Fleming, Henry
item HASSAN, HOSNI - NCSU
item McFeeters, Roger

Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/26/2003
Publication Date: 6/1/2003
Citation: Passos, F.V., Fleming, H.P., Hassan, H.M., McFeeters, R.F. 2003. Effect of malic acid on the growth kinetics of Lactobacillus plantarum. Applied Microbiology and Biotechnology. 63(2):207-211.

Interpretive Summary: Malic acid is a natural constituent of many fruits and vegetables that are preserved by fermentation. This acid may be broken down during fermentation by certain bacteria into lactic acid and carbon dioxide. This reaction is desired to reduce the acidity in certain types of wines and is undesired in the fermentation of cucumbers because of gaseous spoilage from carbon dioxide accumulation inside the fruit. This basic study helps to explain how malic acid may influence the growth of bacteria during the fermentation of fruits and vegetables. The information will be useful in developing cultures of fermentative bacteria for specific purposes.

Technical Abstract: The fermentation kinetics of Lactobacillus plantarum was studied in a specially designed broth formulated from commercially available, dehydrated components (YTA - yeast extract, trypticase, and ammonium sulfate) in batch and continuous culture. During batch growth in the absence of malic acid in the medium the specific growth rate was 0.20 h-1. Malic acid in the medium, at 2 or 10 mM, increased the specific growth rate of L. plantarum to 0.34 h-1. An increase in the maximum cell yield due to malic acid also was observed. Malic acid in the medium reduced the non-growth-associated (maintenance energy) coefficient and increased the biomass yield in continuous culture, based on calculations from the Luedeking and Piret model. The biomass yield coefficient was estimated as 27.4 or 34.3 mg cells/mmoles hexose in the absence or presence of malic acid, respectively. The maintenance coefficient was estimated as 3.5 or 1.5 mg cell/mmole.h, in the absence or presence of malic acid. These results clearly demonstrate the energy-sparing effect of malic acid on the growth- and non-growth-associated energy requirements for L. plantarum. The quantitative energy-sparing effect for malic acid on L. plantarum has heretofore not been reported to our knowledge.