Ethanol production from dilute‐acid steam exploded lignocellulosic feedstocks using an isolated multistress‐tolerant Pichia kudriavzevii strain

Renewable and low‐cost lignocellulosic wastes have attractive applications in bioethanol production. The yeast Saccharomyces cerevisiae is the most widely used ethanol‐producing microbe; however, its fermentation temperature (30–35°C) is not optimum (40–50°C) for enzymatic hydrolysis in the simultaneous saccharification and fermentation (SSF) process. In this study, we successfully performed an SSF process at 42°C from a high solid loading of 20% (w/v) acid‐impregnated steam explosion (AISE)‐treated rice straw with low inhibitor concentrations (furfural 0.19 g l(−1) and acetic acid 0.95 g l(−1)) using an isolate Pichia kudriavzevii SI, where the ethanol titre obtained (33.4 g(p) l(−1)) was nearly 39% greater than that produced by conventional S. cerevisiae BCRC20270 at 30°C (24.1 g(p) l(−1)). In addition, P. kudriavzevii SI exhibited a high conversion efficiency of > 91% from enzyme‐saccharified hydrolysates of AISE‐treated plywood chips and sugarcane bagasse, although high concentrations of furaldehydes, such as furfural 1.07–1.21 g l(−1), 5‐hydroxymethyl furfural 0.20−0.72 g l(−1) and acetic acid 4.80–7.65 g l(−1), were present. This is the first report of ethanol fermentation by P. kudriavzevii using various acid‐treated lignocellulosic feedstocks without detoxification or added nutrients. The multistress‐tolerant strain SI has greater potential than the conventional S. cerevisiae for use in the cellulosic ethanol industry.