Nisin Fermentation by Lactoccocus lactis subsp. lactis Using Plastic Composite Supports in Biofilm Reactors

Jamie A Bober, Ali Demirci

Abstract


Novel plastic composite supports (PCS), composed of equal parts polypropylene and agricultural
products, were evaluated as supports for biofilm production in the bioreactor. Various reduced
nitrogen content media (2.5 – 10 g/L yeast extract and 2.5 – 10 g/L peptone) were tested with
equal parts of PCS rings and discs during 48-hr repeated-batch fermentations for nisin
production and compared to a suspended-cell culture during pH controlled (pH 6.8) and pH
uncontrolled fermentations. Also, fed-batch fermentation with glucose addition was attempted to
prevent glucose depletion during fermentation. Results demonstrated that there was no
significant increase in nisin production or productivity rates using PCS with any reduced content
media over the suspended-cell control during either pH condition. Attempts to increase glucose
concentration in the fed-batch fermentations slightly improved nisin production. The
metabolism of nisin production and possible nisin absorption by L. lactis cells can be limiting
factors which shadow the capability of PCS. It is very clear that nisin starts to be
degraded/absorbed after reaching a maximum level even for suspension-cell culture
fermentation. Therefore, further research is needed to eliminate or minimize nisin
degradation/absorbtion.

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