Sugar Fermentation by Non-conventional Hansenu-La Polymorpha Yeast to Co-produce Methanol, Ethanol and Butanol

Hansenula polymorpha is a non-conventional, methylotrophic, and thermo-tolerant yeast well known for the industrial production of recombinant proteins. However, the research to evaluate this yeast potential for sugar fermentation to produce alcohols for biofuel applications is at an infant stage. For research advancement, the present work investigated the wild type H. polymorpha strain (DSM 70277) for the co-production of methanol, ethanol, and butanol using a batch fermentation reactor and performing experiments at an ideal temperature of 40°C with a pH of 5.5 using different sugars (fructose, glucose, and xylose) as substrates. The maximum specific growth rates (h-1) of H. polymorpha yeast were 0.59–3.02 for fructose, 0.08–2.60 for glucose, and 0.06–0.08 for xylose. The overall yields (g/g) of methanol were higher from fructose (0.132–0.226) than glucose (0.020–0.021) and xylose (0.009–0.030). Ethanol overall yield (g/g) from fructose (0.130–0.325) was more than glucose (0.054–0.167), and xylose (0.042–0.068). The overall butanol yield (g/g) ranged from 0.018–0.031 (fructose), 0.017 (glucose), and 0.009–0.010 (xylose). Due to the methylotrophic nature of H. polymorpha, a shorter time (preferably 2 h) was found suitable for co-production of methanol, ethanol, and butanol.