Yu-Cai He

One-pot chemo-enzymatic synthesis of furfuralcohol from xylose

Furfuralcohol (FOL) is an important intermediate for the production of lysine, ascorbic acid, and lubricants. It can be used as a hypergolic fuel in rocketry. In this study, it was attempted to synthesize FOL from xylose by tandem catalysis with solid acid SO42-/SnO2-Montmorillonite and recombination Escherichia coli CCZU-K14 whole cells. Using SO42-/SnO2-Montmorillonite (3.0wt% dosage) as catalyst, a highest furfural yield of 41.9% was achieved from xylose at 170°C for 20min. Furthermore, Escherichia coli CCZU-K14 whole cells were used for bioconverting furfural to FOL. The optimum biocatalytic reaction temperature, reaction pH, cosubstrate concentration, and substrate concentration were 30°C, 6.5, 1.5mol glucose/mol furfural, and 200mM, respectively. Finally, the yield of FOL from 200mM furfural was achieved to 100% by Escherichia coli CCZU-K14 whole cells after 24h. In conclusion, this strategy show high potential application for the effective synthesis of FOL.

One-pot conversion of biomass-derived xylose to furfuralcohol by a chemo-enzymatic sequential acid-catalyzed dehydration and bioreduction

One-pot furfuralcohol (FOL) production via dehydration of corncob-derived xylose followed by bioreduction of furfural has been described. The synthesized biocompatible solid acid catalyst SO42−/SnO2-attapulgite has been characterized and used for the dehydration of xylose-rich hydrolysate, and the highest furfural yield of 44% is achieved when employing 3.6 wt% catalyst loading at 170 °C for 20 min. The recombinant Escherichia coli CCZU-A13 harboring a NADH-dependent reductase (SsCR) is found to catalyze the bioreduction of furfural to FOL, the whole-cell catalyst could tolerate as high as 300 mM furfural substrate to give 221 mM FOL after 12 h of reaction under the optimum conditions (1.0 mM glucose per mM furfural, 30 °C, pH 6.5, 0.1 g wet cells per mL). The two processes are successfully combined in a one-pot manner to transform the xylose-rich hydrolysate to furfural, and then to FOL with 44% yield based on the starting material xylose (100% FOL yield for the bioreduction step). Finally, recycling experiments for the carrageenan immobilized whole-cell and solid acid catalyst in one-pot FOL production are conducted; both catalysts show excellent recyclability and no obvious decrease in activity is detected after 5 cycles of reaction. The developed one-pot chemo-enzymatic approach is greatly useful for practical green FOL production from renewable biomass resources.

Chemical-enzymatic conversion of corncob-derived xylose to furfuralcohol by the tandem catalysis with SO 4 2- /SnO 2 -kaoline and E. coli CCZU-T15 cells in toluene-water media

One-pot synthesis of furfuralcohol from corncob-derived xylose was attempted by the tandem catalysis with solid acid SO42-/SnO2-kaoline and recombination Escherichia coli CCZU-T15 whole-cells in the toluene-water media. Using SO42-/SnO2-kaoline (3.5wt%) as catalyst, the furfural yield of 74.3% was obtained from corncob-derived xylose in the toluene-water (1:2, v:v) containing 10mM OP-10 at 170°C for 30min. After furfural liquor was mixed with corncob-hydrolysate from the enzymatic hydrolysis of oxalic acid-pretreated corncob residue, furfural (50.5mM) could be completely biotransformed to furfuralcohol with Escherichia coli CCZU-T15 whole-cells harboring an NADH-dependent reductase (ClCR) in the toluene-water (1:3, v:v) containing 12.5mM OP-10 and 1.6mM glucose/mM furfural at 30°C and pH 6.5. Furfuralcohol was obtained at 13.0% yield based on starting material corncob (100% furfuralcohol yield for bioreduction of furfural step). Clearly, this one-pot synthesis of furfuralcohol strategy shows high potential application for the effective utilization of corncob.

Biological synthesis of 2,5-bis(hydroxymethyl)furan from biomass-derived 5-hydroxymethylfurfural by E. coli CCZU-K14 whole cells

Biocatalytic upgrading of bio-based platform chemical 5-hydroxymethylfurfural (5-HMF) to 2,5-bis(hydroxymethyl)furan (BHMF) is currently of great interest due to the product specificity, mild reaction and high efficiency. In this work, 200mM 5-HMF could be effectively biotransformed to BHMF at 90.6% with highly 5-HMF-tolerant recombinant E. coli CCZU-K14 whole cells at pH 6.5 and 30°C under the optimum reaction conditions (cosubstrate glucose 1.0mol glucose/(mol 5-HMF), D-xylose 400mM, l-glutamic acid 250mM, Mg2+ 1.5mM, 0.2mol β-cyclodextrin/(mol 5-HMF), CTAB (cetyltrimethyl ammonium bromide) 12.5mM, and 0.1g wet cells/mL). It was found that E. coli CCZU-K14 was highly tolerant to 5-HMF (up to 400mM). Effective bioreduction of biomass-derived 5-HMF (≤200) to BHMF was successfully demonstrated in this study. In conclusion, this strategy showed high potential application for the synthesis of BHMF.

Effective enzymatic in situ saccharification of bamboo shoot shell pretreated by dilute alkalic salts sodium hypochlorite/sodium sulfide pretreatment under the autoclave system

In this study, dilute alkali salts (0.6% NaClO, 0.067% Na2S) pretreatment at 10% sulfidity under the autoclave system at 120°C for 40min was used for pretreating bamboo shoot shell (BSS). Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated BSS solid residue. After 72h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50g/L pretreated BSS in dilute NaClO/Na2S media could be obtained at 31.11 and 20.32g/L, respectively. Finally, the obtained BSS-hydrolysates containing alkalic salt NaClO/Na2S resulted in slightly negative effects on the ethanol production. Glucose in BSS-hydrolysates was fermented from 20.0 to 0.17g/L within 48h, and an ethanol yield of 0.41g/g glucose, which represents 80.1% of the theoretical yield, was obtained. This study provided an effective strategy for potential utilization of BSS.

Biodegradation of alkali lignin by a newly isolated Rhodococcus pyridinivorans CCZU-B16

Based on the Prussian blue spectrophotometric method, one high-throughput screening strategy for screening lignin-degrading microorganisms was built on 24-well plate at room temperature. One high activity of alkali lignin-degrading strain Rhodococcus pyridinivorans CCZU-B16 was isolated from soil. After the optimization of biodegradation, 30.2% of alkali lignin (4xa0g/L) was degraded under the nitrogen-limited condition (30/1 of C/N ratio; g/g) at 30xa0°C for 72xa0h. It was found that syringyl (S) units and guaiacyl (G) in lignin decreased after biodegradation. Moreover, the accumulated lipid in cells had a fatty acid profile rich in C16 and C18 with four major constituent fatty acids including palmitic acid (C16:0; 22.4%), palmitoleic acid (C16:1; 21.1%), stearic acid (C18:0; 16.2%), and oleic acid (C18:1; 23.1%). In conclusion, Rhodococcus pyridinivorans CCZU-B16 showed high potential application in future.Graphical abstract

Enzymatic in situ saccharification of sugarcane bagasse pretreated with low loading of alkalic salts Na2SO3/Na3PO4 by autoclaving

Sugarcane bagasse (SCB) is an abundant, renewable and inexpensive agricultural byproduct for the production of biofuel and other biobased products. To effectively saccharify SCB with cellulases, combination with dilute alkali salts Na2SO3/Na3PO4 (0.4% Na3PO4, 0.03% Na2SO3) at 7.5% sulfidity and hot water (DASHW) in one-pot pretreatment media by autoclaving at 110°C for 40min was attempted to pretreat SCB in this study. Furthermore, FT-IR, XRD and SEM were employed to characterize the changes in the cellulose structural characteristics (porosity, morphology, and crystallinity) of the pretreated Na2SO3/Na3PO4-SCB solid residue, which indicated that combination pretreatment could effectively remove lignin and hemicellulose for enhancing enzymatic saccharification. After 72h, the reducing sugars and glucose from the enzymatic in situ hydrolysis of 50g/L Na2SO3/Na3PO4-SCB in dilute Na2SO3/Na3PO4 (0.27% Na3PO4, 0.02% Na2SO3) media were obtained at 33.8 and 21.8g/L, respectively. Finally, the SCB-hydrolysates containing 20g/L glucose were used for ethanol fermentation in the presence of dilute alkali salts. After 48h, the ethanol yield was 0.42g ethanol/g glucose, which represents 82.1% of the theoretical yield. In conclusion, this study provided an effective pretreatment strategy for enhancing SCBs saccharification, which has potential application of other lignocellulosic materials.

Chemo-enzymatic synthesis of furfuralcohol from chestnut shell hydrolysate by a sequential acid-catalyzed dehydration under microwave and Escherichia coli CCZU-Y10 whole-cells conversion

In this study, chemo-enzymatic synthesis of furfuralcohol from biomass-derived xylose was successfully demonstrated by a sequential acid-catalyzed dehydration under microwave and whole-cells reduction. After dry dewaxed chestnut shells (CNS, 75u202fg/L) was acid-hydrolyzed with dilute oxalic acid (0.5u202fwt%) at 140u202f°C for 40u202fmin, the obtained CNS-derived xylose (17.9u202fg/L xylose) could be converted to furfural at 78.8% yield with solid acid SO42-/SnO2-Attapulgite (2.0u202fwt% catalyst loading) in the dibutyl phthalate-water (1:1, v:v) under microwave (600u202fW) at 180u202f°C for 10u202fmin. In the dibutyl phthalate-water (1:1, v/v) media at 30u202f°C and pH 6.5, the furfural liquor (47.0u202fmM furfural) was biologically converted to furfuralcohol by recombinant Escherichia coli CCZU-Y10 whole-cells harboring an NADH-dependent reductase (PgCR) without extra addition of NAD+ and glucose, and furfural was completely converted to furfuralcohol after 2.5u202fh. Clearly, this one-pot synthesis strategy can be effectively used for furfuralcohol production.

Effective Utilization of Carbohydrate in Corncob to Synthesize Furfuralcohol by Chemical–Enzymatic Catalysis in Toluene–Water Media

In this study, carbohydrates (cellulose plus hemicellulose) in corncob were effectively converted furfuralcohol (FOL) via chemical–enzymatic catalysis in a one-pot manner. After corncob (2.5xa0g, dry weight) was pretreated with 0.5xa0wt% oxalic acid, the obtained corncob-derived xylose (19.8xa0g/L xylose) could be converted to furfural at 60.1% yield with solid acid catalyst SO42−/SnO2-attapulgite (3.6xa0wt% catalyst loading) in the water–toluene (3:1, v/v) at 170xa0°C for 20xa0min. Moreover, the oxalic acid-pretreated corncob residue (1.152xa0g, dry weight) was enzymatically hydrolyzed to 0.902xa0g glucose and 0.202xa0g arabinose. Using the corncob-derived glucose (1.0xa0mM glucose/mM furfural) as cosubstrate, the furfural liquor (48.3xa0mM furfural) was successfully biotransformed to FOL by recombinant Escherichia coli CCZU-A13 cells harboring an NADH-dependent reductase (SsCR) in the water-toluene (4:1, v/v) under the optimum conditions (50xa0mM PEG-6000, 0.2xa0mM Zn2+, 0.1xa0g wet cells/mL, 30xa0°C, pHxa06.5). After the bioreduction for 2xa0h, FAL was completely converted to FOL. The FOL yield was obtained at 0.11xa0g FOL/g corncob. Clearly, this one-pot synthesis strategy shows high potential application for the effective synthesis of FOL.

One-pot chemo-enzymatic conversion of D-xylose to furfuralcohol by sequential dehydration with oxalic acid plus tin-based solid acid and bioreduction with whole-cells

In this study, organic acid could be used as co-catalyst for assisting solid acid SO42-/SnO2-argil to convert hemicellulose-derived D-xylose into furfural. The relationship between pKa of organic acid and turnover frequency (TOF) of co-catalysis with organic acid plus SO42-/SnO2-argil was explored on the conversion of D-xylose to furfural. Oxalic acid (pKau202f=u202f1.25) (0.35u202fwt%) was found to be the optimum co-catalyst for assisting SO42-/SnO2-argil (3.6u202fwt%) to synthesize furfural from D-xylose (20u202fg/L) at 180u202f°C for 20u202fmin, and the furfural yield and TOF could be obtained at 57.07% and 6.26u202fh-1, respectively. Finally, the obtained furfural (107.6u202fmM) could be completely biotransformed to furfuralcohol by recombinant Escherichia coli CCZU-K14 whole-cells at 30u202f°C and pH 6.5 in the presence of 1.5u202fmol glucose/mol furfural and 400u202fmM D-xylose. Clearly, this strategy shows high potential application for the effective synthesis of furfuralcohol from biomass-derived D-xylose.