Xylitol production from lignocellulosic whole slurry corn cob by engineered industrial Saccharomyces cerevisiae PE-2

Abstract

In this work, the industrial Saccharomyces cerevisiae PE-2 strain, presenting innate capacity for xylitol accumulation, was engineered for xylitol production by overexpression of the endogenous GRE3 gene and expression of different xylose reductases from Pichia stipitis. The best-performing GRE3-overexpressing strain was capable to produce 148.5 g/L of xylitol from high xylose-containing media, with a 0.95 g/g yield, and maintained close to maximum theoretical yields (0.89 g/g) when tested in non-detoxified corn cob hydrolysates. Furthermore, a successful integrated strategy was developed for the production of xylitol from whole slurry corn cob in a presaccharification and simultaneous saccharification and fermentation process (15% solid loading and 36 FPU) reaching xylitol yield of 0.93 g/g and a productivity of 0.54 g/L·h. This novel approach results in an intensified valorization of lignocellulosic biomass for xylitol production in a fully integrated process and represents an advance towards a circular economy.

Development of a sustainable bioprocess based on green technologies for xylitol production from corn cob

“…The pretreatment severity was based on previous works that have shown that the use of 12 g of corn cob per 100 g of water lead to maximum concentration of xylooligosaccharides (Garrote et al, 2008;Rivas et al, 2006). In order to reduce the water consumption in the process and increase the xylose concentration in the liquid fraction (hydrolysate), the solid loading of corn cob was evaluated in the range of 20 to 30 g of corn cob per 100 g of water at T max of 205°C (S 0 = 3.89) (Baptista et al, 2018). The use of high-solid loadings in the pretreatment minimizes the water consumption and reduces the energy required for heating, improving the economic and environmental sustainability of the process (Modenbach and Nokes, 2012; Jesus et al, 2017).…”

“…The yeast strain used in this work was the yeast strain Saccharomyces cerevisiae PE-2, isolated from 1 st generation bioethanol plants in Brazil, (Basso et al, 2008;Pereira et al, 2014aPereira et al, , 2014bPereira et al, 2011Pereira et al, , 2010 overexpressing the endogenous GRE3 gene, S. cerevisiae PE-2-GRE3 (Baptista et al, 2018). Yeast strain was maintained at 4°C on YPD plates (10 g/L yeast extract, 20 g/L peptone, 20 g/L glucose and 20 g/L agar) supplemented with 200 mg/L of geneticin (G418).…”

“…However, xylitol yields are limited by the use of xylose as carbon source for yeast growth and maintenance energy. To overcome this limitation, the expression of enzymes with xylose reductase activity in Saccharomyces cerevisiae, naturally incapable of xylose utilization, has shown to increase the conversion of xylose into xylitol close to the maximum theoretical yield (∼100%), since the produced xylitol is not further metabolized (Baptista et al, 2018;Hallborn et al, 1991;Jo et al, 2015;Kogje and Ghosalkar, 2016). Moreover, the possibility of using robust S. cerevisiae strains, isolated from harsh environmental industrial conditions, with higher tolerance to the lignocellulosic-derived inhibitors represents another advantage for xylitol production in lignocellulose-based processes (Cunha et al, 2019;Pereira et al, 2014aPereira et al, , T 2014b.…”

“…Moreover, the possibility of using robust S. cerevisiae strains, isolated from harsh environmental industrial conditions, with higher tolerance to the lignocellulosic-derived inhibitors represents another advantage for xylitol production in lignocellulose-based processes (Cunha et al, 2019;Pereira et al, 2014aPereira et al, , T 2014b. Considering this, the S. cerevisiae PE-2 industrial strain presenting innate capacity for xylitol accumulation (Romani et al, 2015), was recently engineered to overexpress an endogenous aldose reductase with xylose reductase activity (encoded by GRE3 gene) and efficiently used as whole-cell biocatalyst for xylitol production (Baptista et al, 2018).…”

Coproduction of xylose and biobutanol from corn stover via recycling of sulfuric acid pretreatment solution

“…Since the dry mass content is generally less than 13%, the xylose concentration after hydrolysis of corn stover was reported to be 16.4-20.5 g/L [10,34]. However, a significantly higher substrate (xylose) concentration of about 200 g/L is required for xylitol production [35,36]. Vacuum evaporation concentration is undesirable, due to its high energy consuming and generation of inhibitors such as furfural and hydroxyl methyl furfural (HMF).…”