AN INTERLABORATORY COMPARISON OF THE PERFORMANCE OF ETHANOL-PRODUCINGMICROORGANISMS IN A XYLOSE-RICH ACID HYDROLYSATE

A xylose-rich, dilute-acid-pretreated corncob hydrolysate was fermente d by Escherichia coli ATCC 11303, recombinant (rec) E. coli B (pLOI297 and KO11), Pichia stipitis (CBS 5773, 6054 and R), Saccharomyces cere visiae isolate 3 in combination with xylose isomerase, rec S. cerevisi ae (TJ1, H550 and H477) and Fusarium oxysporum VTT-D-80134 in an inter laboratory comparison. The micro-organisms were studied according to t hree different options: (A) fermentation under consistent conditions, (B) fermentation under optimal conditions for the organism, and (C) fe rmentation under optimal conditions for the organism with detoxificati on of the hydrolysate. The highest yields of ethanol, 0.24 g/g (A), 0. 36 g/g (B) and 0.54 g/g (C), were obtained from rec E. coli B, KO11. P . stipitis and F. oxysporum were sensitive to the inhibiters present i n the hydrolysate and produced a maximum yield of 0.34 g/g (C) and 0.0 4 g/g (B), respectively. The analysis of the corn-cob hydrolysate and aspects of process economy of the different fermentation options (pH, sterilization, nutrient supplementation, adaptation, detoxification) a re discussed.