Candida lignohabitans for organic acids production from lignocellulosic material

CANDIDA LIGNOHABITANS FOR ORGANIC ACID PRODUCTION FROM LIGNOCELLULOSIC MATERIAL 1. Introduction: Microbial conversion of lignocellulosic biomass as basis for chemical production depends on microbial cell factories, which efficiently convert hexoses as well as pentoses into the desired products. 2. Concept and methodology: We suggest the unconventional yeast species, Candida lignohabitans, for the efficient fermentation of biomass derived feedstocks. Glucose, galactose, mannose, arabinose and xylose are efficiently metabolized by Candida lignohabitans, in pure form or as mixtures. To test the performance of this microorganism on real substrates a variety of lignocellulosic materials including saw dust, wood chips, christmas tree and Miscanthus have been pretreated by steam explosion and subsequently enzymatically hydrolysed. Liquefaction of the biomass was successful and led to hydrolysates with sugar concentrations of 50-80 g/L. C. lignohabitans grew very well on the hydrolysates, accumulating biomass and varying amounts of ethanol as natural fermentation product. Genetic manipulation of C. lignohabitans with novel-established tools has also shown to be possible. GFP expression under the control of the endogenous GAP promoter lead to a stable, strong cytosolic fluorescence. In order to test the suitability of this yeast for chemical production, various heterologous enzymes have been expressed. Significant amounts of organic acids - as examples for value added chemicals - could be produced, both during the growth on pure sugars and on enzymatic hydrolysates.