Statistical optimization of simple culture conditions to produce biomass of an ochratoxigenic mould biocontrol yeast strain

Abstract

Aim: To maximize biomass production of an ochratoxigenic mould-controlling strain of Lachancea thermotolerans employing response surface methodology (RSM). Methods and Results: Using Plackett-Burman screening designs (PBSD) and central composite designs (CCD), an optimized culture medium containing (gl -1): fermentable sugars (FS), 139·2, provided by sugar cane molasses (CMz), (NH 4) 2HPO 4 (DAP), 9·0, and yeast extract (YE), 2·5, was formulated. Maximal cell concentration obtained after 24h at 28°C was 24·2gl -1cell dry weight (CDW). The mathematical model obtained was validated in experiments performed in shaken-flask cultures and also in aerated bioreactors. Maximum yield and productivity values achieved were, respectively, of 0·23g CDW/g FS in a medium containing (gl -1): FS, 87·0; DAP, 7·0; YE, 1·0; and of 0·96g CDW l -1 h -1 in a medium containing (gl -1): FS, 150·8 plus DAP, 6·9. Conclusions: Optimized culture conditions for maximizing yeast biomass production determined in flask cultures were applicable at a larger scale. The highest yield values were attained in media containing relatively low-CMz concentrations supplemented with DAP and YE. Yeast extract would not be necessary if higher productivity is the aim. Significance and Impact of the Study: Cells of L. thermotolerans produced aerobically could be sustainably produced in a medium just containing cheap carbon, nitrogen and phosphorus sources. Response surface methodology allowed the fine-tuning of cultural conditions.