Hemicellulosic Bioethanol Production from Fast-Growing Paulownia Biomass

Abstract

In order to exploit a fast-growing Paulownia hardwood as an energy crop, a xylose-enriched hydrolysate was obtained in this work to increase the ethanol concentration using the hemicellulosic fraction, besides the already widely studied cellulosic fraction. For that, Paulownia elongata x fortunei was submitted to autohydrolysis treatment (210 °C or S0 of 4.08) for the xylan solubilization, mainly as xylooligosaccharides. Afterwards, sequential stages of acid hydrolysis, concentration, and detoxification were evaluated to obtain fermentable sugars. Thus, detoxified and non-detoxified hydrolysates (diluted or not) were fermented for ethanol production using a natural xylose-consuming yeast, Scheffersomyces stipitis CECT 1922, and an industrial Saccharomyces cerevisiae MEC1133 strain, metabolic engineered strain with the xylose reductase/xylitol dehydrogenase pathway. Results from fermentation assays showed that the engineered S. cerevisiae strain produced up to 14.2 g/L of ethanol (corresponding to 0.33 g/g of ethanol yield) using the non-detoxified hydrolysate. Nevertheless, the yeast S. stipitis reached similar values of ethanol, but only in the detoxified hydrolysate. Hence, the fermentation data prove the suitability and robustness of the engineered strain to ferment non-detoxified liquor, and the appropriateness of detoxification of liquor for the use of less robust yeast. In addition, the success of hemicellulose-to-ethanol production obtained in this work shows the Paulownia biomass as a suitable renewable source for ethanol production following a suitable fractionation process within a biorefinery approach.

Ethanol production by Escherichia coli from detoxified lignocellulosic teak wood hydrolysates with high concentration of phenolic compounds

“…Some of the hydrolysates reported in Table 3 were subjected to less severe conditions of hydrolysis such as lower temperatures and holding times followed by detoxification with overliming or overliming + AC (Gupta et al, 2009 ). Nevertheless, the productivity obtained in this work was 1.13–2.5-fold higher even when the SPC concentration after detoxification was 4.6-fold higher than the value reported by Domínguez et al ( 2021 ).…”

“…Versus other processes for ethanol production from hardwood hydrolysates, the productivity and ethanol titer achieved here are considerably higher than most reported values (Table 3 ). It is well known that hardwoods contain a high concentration of lignin-derived compounds (Domínguez et al, 2021 ). Most of them are toxic for microorganisms and constitute a bottleneck for the utilization of sugar-rich hardwoods in fermentation processes, especially when they are compared with other lignocellulosic biomasses.…”

Response mechanisms of Saccharomyces cerevisiae to the stress factors present in lignocellulose hydrolysate and strategies for constructing robust strains

“…(g/L) Y E/S (g/g) Refs. TP1 TFA7 PGK1 P - PAD1 - PGK1 T ShBle ENO1 P - ICT1 - ENO1 T 2% synthetic media + 40% v/v concentrated hardwood spent sulphite liquor Glucose 34.70 g/L xylose 92.70 g/L Weak acids 15.70 g/L, furans 2.30 g/L, phenolics 2.00 g/L 12.20 0.26 [ 26 ] s6H3T10 UBI4 P -HAA1-HAA1 T UBI4 P -TYE7-TYE7 T Corn stover Glucose 93.88 g, xylose 14.81 g (Each kilogram of pretreated slurry) Acetic acid 2.82 g, formic acid 1.53 g, furfural 0.21 g, 5-HMF 0.37 g, total phenols 2.33 g (Each kilogram of pretreated slurry) 47.50 0.44 [ 27 ] MEC1133 PE-2, gre3::natMX4/gre3::kanMX4, pMEC149 Paulownia elongata x fortunei Glucose < 5.00 g/L, xylose 55.80 g/L Formic acid 0.71 g/L, acetic acid 5.67 g/L, levulinic acid 1.03 g/L, HMF 0.69 g/L, furfural 0.65 g/L, total phenols 8.25 g/L 14.20 0.33 [ 28 ] XUSAE57 BY4741 / xylA3* / TAL1 / XKS1 / △gre3 / △pho13 /evolved Sugarcane bagasse Glucose 26.20 g/L xylose 27.70 g/L Acetic acid 2.50 g/L, phenolics 0.80 g/L ~ 23.00 0.49 [ 29 ] PE-HAA1/PRS3 PE-2 ΔGRE3 , pMEC9003 Paulownia tomentosa Glucose 30.00 g/L, xylose 11.30 g/L Acetic acid 5.84 g/L, furfural 1.96 g/L, HMF 0.72 g/L 8.15 …”

Effect of Hydrolysis Time and Sulfuric Acid Concentration on Reducing Sugar Content on Corn Cob Hydrolysis

“…The use of non-renewable energy fueled by fossil fuels is almost used in all activities, both from the household, and transportation to industrial scale, which if used continuously will affect the number of fossil fuels, which are increasingly scarce and depleting [1,2]. The depletion of fossil fuels is a reference for producing biofuels [3]. Biofuel can be produced by utilizing lignocellulosic waste so that it does not interfere with food conditions and is instead environmentally friendly, one of the uses is by producing bioethanol [4].…”