Application of Pichia kudriavzevii NBRC1279 and NBRC1664 to Simultaneous Saccharification and Fermentation for Bioethanol Production

Abstract

Simultaneous saccharification and fermentation (SSF) is capable of performing enzymatic saccharification and fermentation for biofuel production in a single vessel. Thus, SSF has several advantages such as simplifying the manufacturing process, operating easily, and reducing energy input. Here, we describe the application of Pichia kudriavzevii NBRC1279 and NBRC1664 to SSF for bioethanol production. When each strain was incubated for 144 h at 35 °C with Japanese cedar particles, the highest ethanol concentrations were reached 21.9 ± 0.50 g/L and 23.8 ± 3.9 g/L, respectively. In addition, 21.6 ± 0.29 g/L and 21.3 ± 0.21 g/L of bioethanol were produced from Japanese eucalyptus particles when each strain was incubated for 144 h at 30 °C. Although previous methods require pretreatment of the source material, our method does not require pretreatment, which is an advantage for industrial use. To elucidate the different characteristics of the strains, we performed genome sequencing and genome comparison. Based on the results of the eggNOG categories and the resulting Venn diagram, the functional abilities of both strains were similar. However, strain NBRC1279 showed five retrotransposon protein genes in the draft genome sequence, which indicated that the stress tolerance of both strains is slightly different.

Transcription Analysis of the Acid Tolerance Mechanism of Pichia kudriavzevii NBRC1279 and NBRC1664

“…Moreover, it appears that P. kudriavzevii NBRC1664 has higher acid tolerance than P. kudriavzevii NBRC1279 because P. kudriavzevii NBRC1664 showed remarkable growths in the presence of inorganic acids such as hydrochloric acid and sulfuric acid and the time to reach the stationary phase is short in the presence of organic acids. A higher yield of ethanol is expected using P. kudriavzevii NBRC1664 than P. kudriavzevii NBRC1279 when performing SSF with acidbased pretreatment methods, which is consistent with the results of our previous study that carried out SSF with particles from Japanese cedar or eucalyptus as raw materials [7]. Thus, in the future, we will use the P. kudriavzevii NBRC1664 strain to develop SSF with acid-based pretreatment methods.…”

“…To simplify the production process and ease of operation, and reduce the required energy input, simultaneous saccharification and fermentation (SSF) has been performed for ethanol production using the thermostable yeast strains Pichia kudriavzevii NBRC1279 and NBRC1664 with particles from Japanese cedar or eucalyptus [7]. Compared to the above method, the manufacturing process is simpler because enzymatic hydrolysis and fermentation are simultaneously performed in the same vessel.…”

Exploring Natural Fermented Foods as a Source for New Efficient Thermotolerant Yeasts for the Production of Second-Generation Bioethanol

“…There are few reports dealing with SSF using hard biomass and the species of P. kudriavzevii. For example, Akita et al [37] stated that P. kudriavzevii NBRC1279 and NBRC1664 produced 21.6 g/L and 21.3 g/L ethanol, respectively, from Japanese eucalyptus at 30 • C for 144 h.…”

Industrialization progress of lignocellulosic ethanol

“…However, traditionally Saccharomyces cerevisiae which is used for ethanol production is an efficient glucose consumer but unable to utilize xylose. Therefore, scientists try to introduce the xylose metabolic pathway into Saccharomyces cerevisiae through genetic engineering, so that Saccharomyces cerevisiae has the ability to ferment xylose to improve ethanol yield, but there is still no strain that is efficient and perfect [83][84][85][86], and the efficient strain should be able to tolerate high concentration inhibitors, make full use of the difficult fermentable sugar in the enzymatic hydrolysate, and have high ethanol yield.…”