Summary: 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 BCRC 20270 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.

Utilization of renewable and low-cost lignocellulosic wastes has received major focus in industrial lactic acid production. The use of high solid loadings in biomass pretreatment potentially offers advantages over low solid loadings including higher lactic acid concentration with decreased production and capital costs. In this study, an isolated Enterococcus faecalis SI with optimal temperature 42 °C was used to produce optically pure l-lactic acid (> 99%) from enzyme-saccharified hydrolysates of acid-impregnated steam explosion (AISE)-treated plywood chips. The l-lactic acid production increased by 10% at 5 L scale compared to the similar fermentation scheme reported by Wee et al. The fermentation with a high solid loading of 20% and 35% (w/v) AISE-pretreated plywood chips had been successfully scaled up to process development unit scale (100 L) and pilot scale (9 m3), respectively. This is the first report of pilot-scale lignocellulosic lactic acid fermentation by E. faecalis with high lactic acid titer (nearly 92 g L−1) and yield (0.97 kg kg−1). Therefore, large-scale l-lactic acid production by E. faecalis SI shows the potential application for industries.

The isolated bacterium Lactobacillus plantarum is strongly tolerant of lignocellulose-derived inhibitory compounds and possesses the ability to produce lactic acid in the presence of 8.0 g/L furfural, 6.0 g/L hydroxymethylfurfural, 4.0 g/L vanillin, and 4.0 g/L syringaldehyde. This bacterium was used in an integrated simultaneous saccharification and fermentation (SSF) process for the production of lactic acid using whole rice straw slurry (with a high solids content of 17%) that had been pretreated with dilute sulfuric acid. This method achieved a lactic acid concentration of 65.6 g/L, which corresponded to a cellulose-to-lactic acid conversion yield of 69%. These results demonstrated that isolated bacterium and the proposed integrated SSF process are able to produce high concentrations of lactic acid. Furthermore, this proposed process does not require detoxification and had a conversion efficiency that is comparable to that obtained using the conventional SSF process, which requires the addition of fresh water. Therefore, it was concluded that the proposed process is promising for commercial lactic acid production and could make the production of lactic acid from lignocellulosic biomass more practical in the future.

Because of their lower environmental impact, biodegradable polymers such as polyhydroxyalkanoates (PHAs) produced within cultured bacteria represent promising alternatives to petroleum-based plastics. PHA production in flasks yielded optimal results with a carbon-to-nitrogen ratio of 22. The 5-L scale experimental results revealed that when glucose was used as the carbon source, Cupriavidus necator could produce 4.74 g/L PHA with 77.6% of PHA content in the microorganism 72 h after the initiation of the experiment. When the hydrolysis liquid from inedible rice was used as the carbon source, the highest concentration of PHA and ratio of PHA content in the microorganism were 4.82 g/L and 68.6%, respectively, after 72 h. Using the hydrolysis liquid from inedible rice as the carbon source reduced the culture cost and shortened the culture time, without affecting the structure of the PHA during production. Using the hydrolysis liquid from rice as the carbon source in PHA production (by C. necator) yielded optimal results, and the results may serve as a reference for applications involving other PHA-producing bacteria. Employing alternative carbon sources to culture bacteria might become a means of increasing the productivity and ensuring the quality of PHA products in the future.