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 (g l(-1) ): fermentable sugars (FS), 139·2, provided by sugar cane molasses (CMz), (NH(4) )(2) HPO(4) (DAP), 9·0, and yeast extract (YE), 2·5, was formulated. Maximal cell concentration obtained after 24 h at 28°C was 24·2 g l(-1) cell 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 0·23 g CDW/g FS in a medium containing (g l(-1) ): FS, 87·0; DAP, 7·0; YE, 1·0; and of 0·96 g CDW l(-1) h(-1) in a medium containing (g l(-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.
