Robust Microorganisms and Process Strategies– The Key to Successful Lignocellulose Based Ethanol Production

Other conference contribution, 2012

Fermentation of lignocellulose raw materials bear a lot of promises, and leave a number of challenges before it can be commercialized with good economical perspectives. The development of the process is driven towards higher gravities and better process integration in order to optimize energy input and water usage. From a microbial point of view this leads to more stressful conditions, including high inhibitor concentrations, high ethanol concentrations and poor nutritional conditions in the hydrolysates to be fermented. One way of addressing these challenges is to optimize the fermentation strategy and here a novel SSF ethanol process configuration involving feeding of substrate, enzyme and yeast will be presented. We demonstrate that this strategy ensures active metabolic state of yeast throughout the process leading to increased ethanol yield and productivity. Another strategy is to improve the microbial robustness by different strain engineering approaches. The inhibitory compounds may influence the cellular metabolism in a number of ways, including direct damage on cellular functions or by perturbations of the cellular energy and redox metabolism. During this presentation the concept of microbial robustness will be discussed and examples of strategies to the design of increased microbial robustness will be given.