Hemicellulase Preparations: Inhibition relief and Increased Yields

There were two primary goals of this study: The first was to demonstrate that hemicellulase enzyme preparations can hydrolyze 35% or more of the xylo-oligomers present in dilute acid pretreated corn stover to their monomeric forms. The second was to obtain data to determine whether or not the addition of a xylanase enzyme preparation relieves a perceived lag in growth of r. Zymomonas.  The top performing commercial xylanase preparation was able to hydrolyze nearly 60% of the xylo-oligomers present in a dilute acid pretreated corn stover hydrolysate at a loading of 0.05 mg/g within 24 hours that would normally have been lost to waste water treatment. This additional monomeric fermentable sugar will increase yields and titers, and improve costs.  Approximately 30% of the xylo-oligomers appear to be recalcitrant to enzymatic hydrolysis with the commercial preparations tested, even at very high xylanase loadings. We found that there appears to be no apparent effect on the growth of r. Zymomonas when the C5 hydrolysate liquors are pre-incubated with a commerical xylanase preparation before inoculation with the microorganism. In addition, no effect on ethanol production was found, as this appears to be more dependent on the availability of monomeric sugars during expontential growth.  In contrast, a lag phase in growth and ethanol production was found when using the separated C5 sugar rich stream without the addition of xylanase enzymes.  The xylanase enzymes appear to relieved the inhibition and lag phase.