Repeated batch citrate production by Yarrowia lipolytica using yeast recycling by cross-flow microfiltration

In this work, the feasibility of cell recycle by cross-flow filtration in repeated batch citrate fermentation by Y. lipolytica was assessed by supplying a basic production medium devoid of nitrogen sources either as such (C1) or integrated (C2) with the main cofactors entering the Krebs cycle leading to citric acid. Despite a wide degree of dispersion, the experimental yield coefficients did not show a statistically significant dependence on the number of cell recycles performed, their average value (0.43+/-0.12 g citric acid/g glucose consumed) being practically in line with previous findings. Citrate productivity (R(P)) was correlated to yeast density (X(P)) for any generic i-th production cycle whatever the cell recycling mode used but the specific citrate productivity (m(P)) tended to decrease as the number of cell recycling was increased. Whereas the addition of vitamins to the basic production medium C1 appeared to be unable to maintain cell citrate excretion capability unaltered CFMF allowed cell recovery to be aseptically performed without severe membrane fouling problems provided that no more than 2 or 3 production cycles were performed.