Lignin is the world's greatest renewable aromatic biofeedstock,and it has promising applications in high value-added chemical products.Herein,N-Co/ATP-CZO was used as a catalyst for the depolymerization of alkali ...Lignin is the world's greatest renewable aromatic biofeedstock,and it has promising applications in high value-added chemical products.Herein,N-Co/ATP-CZO was used as a catalyst for the depolymerization of alkali lignin in ethanol and isopropanol systems,and explored the effects of formic acid(FA)amount,reaction time,reaction temperature and other factors on the depolymerization of alkali lignin.Among them,formic acid serves as both catalytic and in situ-hydrogen donor.Ultimately,the highest yield of bio-oil(59.28%(mass)),including 30.05%(mass)of monomer,was obtained after a reaction of FA to alkali lignin mass ratio of 4 and 240°C for 8 h.Among the monomers,the yield of Guaiacol was the highest(5.94%(mass)),followed by 2-methoxy-4-methylphenol(5.74%(mass)).This study,the modification of attapulgite was carried out to reduce the acidity while enhancing the catalytic activity for depolymerization,and the selection of hydrogen donor was investigated.A feasible pathway for lignin depolymerization research was opened.展开更多
This study performed catalytic depolymerization of alkali lignin over Ni-based catalysts.Effects of different promoters(Zr and W),Ni loadings,reaction temperatures,and the addition of formic acid and catalyst on ligni...This study performed catalytic depolymerization of alkali lignin over Ni-based catalysts.Effects of different promoters(Zr and W),Ni loadings,reaction temperatures,and the addition of formic acid and catalyst on lignin conversion and products distribution were all investigated.The result showed that the highest oil yield(40.1%(mass))was obtained at 240℃over Ni_(1.2)/γ-Al_(2)O_(3) promoted by Zr and W species.Quantitative analysis indicates that Zr and W species prefer to lignin depolymerization while Ni active phase prefer to hydrodeoxygenation and hydrogenation.The interconversion of products derived from lignin depolymerization was determined by gas chromatography-mass spectrometer,which demonstrated that phenolic compounds were dominant products in all lignin derived bio-oils,wherein the proportion of vanillin was highest(65.7%)at 180℃,while that of alkyl guaiacols increased with the increase of temperature(from 12.45%at 180℃ to 66.67%at 240℃).Residual lignin obtained after lignin depolymerization was also investigated for detecting differences on functional groups,wherein the disappearing peaks at 1511 cm^(-1)(stretching of aromatic rings),1267,1215 and 1035 cm^(-1)(vibrations of guaiacyl and syringyl units)were detected by Fourier transform infrared spectrometry.Additionally,the higher O/C ratio measured by elemental analysis also confirmed that alkali lignin was depolymerized effectively under mild conditions.展开更多
The conversion of r-carotene to astaxanthin is a complex pathway network, in which two steps of hydroxylation and two steps ofketolation are catalyzed by β-carotene hydroxylase （CrtZ） and β-carotene ketolase （Crt...The conversion of r-carotene to astaxanthin is a complex pathway network, in which two steps of hydroxylation and two steps ofketolation are catalyzed by β-carotene hydroxylase （CrtZ） and β-carotene ketolase （CrtW） respectively. Here, astaxanthin biosynthesis path- way was constructed in Saccharomyces cerevisiae by introducing heterologous CrtZ and CrtW into an existing high r-carotene producing strain. Both genes crtZ and crtW were codon optimized and expressed under the control of constitutive promoters. Through combinatorial expression of CrtZ and CrtW from diverse species, nine strains in dark red were visually chosen from thirty combinations. In all the selected strains, strain SyBE Scl 18060 with CrtW from Brevundimonas vesicu- laris DC263 and CrtZ from Alcaligenes sp. strain PC-1 achieved the highest astaxanthin yield of 3.1 mg/g DCW. Protein phylogenetic analysis shows that the shorter evolutionary distance of CrtW is, the higher astaxanthin titer is. Further, when the promoter of crtZ in strain SyBE_Scl 18060 was replaced from FBAlp to TEFlp, the astaxanthin yield was increased by 30.4% （from 3.4 to 4.5 mg/g DCW）. In the meanwhile, 33.5-fold increase on crtZ transcription level and 39.1-fold enhancement on the transcriptional ratio of crtZ to crtWwere observed at early exponential phase in medium with 4% （w/v） glucose. Otherwise, although the ratio of crtZ to crtW were increased at mid-, late-exponential phases in medium with 2% （w/v） glucose, the transcription level of both crtZ and crtW were actually decreased during the whole timecourse, consequently leading to no significant improve- ment on astaxanthin production. Finally, through high cell density fed-batch fermentation using a carbon source restriction strategy, the production of astaxanthin in a 5-L bioreactor reached to 81.0 mg/L, which was the highest astaxanthin titer reported in yeast. This study provides a reference to greatly enhance lation by employing the key desired compounds accumu- enzyme（s） in microbes.展开更多
基金financially supported by National Natural Science Foundation of China (21774059)。
文摘Lignin is the world's greatest renewable aromatic biofeedstock,and it has promising applications in high value-added chemical products.Herein,N-Co/ATP-CZO was used as a catalyst for the depolymerization of alkali lignin in ethanol and isopropanol systems,and explored the effects of formic acid(FA)amount,reaction time,reaction temperature and other factors on the depolymerization of alkali lignin.Among them,formic acid serves as both catalytic and in situ-hydrogen donor.Ultimately,the highest yield of bio-oil(59.28%(mass)),including 30.05%(mass)of monomer,was obtained after a reaction of FA to alkali lignin mass ratio of 4 and 240°C for 8 h.Among the monomers,the yield of Guaiacol was the highest(5.94%(mass)),followed by 2-methoxy-4-methylphenol(5.74%(mass)).This study,the modification of attapulgite was carried out to reduce the acidity while enhancing the catalytic activity for depolymerization,and the selection of hydrogen donor was investigated.A feasible pathway for lignin depolymerization research was opened.
基金financially supported by the National Natural Science Foundation of China ( 21774059)the Priority Academic Program Development (PAPD) of Jiangsu Higher Education Institutions
文摘This study performed catalytic depolymerization of alkali lignin over Ni-based catalysts.Effects of different promoters(Zr and W),Ni loadings,reaction temperatures,and the addition of formic acid and catalyst on lignin conversion and products distribution were all investigated.The result showed that the highest oil yield(40.1%(mass))was obtained at 240℃over Ni_(1.2)/γ-Al_(2)O_(3) promoted by Zr and W species.Quantitative analysis indicates that Zr and W species prefer to lignin depolymerization while Ni active phase prefer to hydrodeoxygenation and hydrogenation.The interconversion of products derived from lignin depolymerization was determined by gas chromatography-mass spectrometer,which demonstrated that phenolic compounds were dominant products in all lignin derived bio-oils,wherein the proportion of vanillin was highest(65.7%)at 180℃,while that of alkyl guaiacols increased with the increase of temperature(from 12.45%at 180℃ to 66.67%at 240℃).Residual lignin obtained after lignin depolymerization was also investigated for detecting differences on functional groups,wherein the disappearing peaks at 1511 cm^(-1)(stretching of aromatic rings),1267,1215 and 1035 cm^(-1)(vibrations of guaiacyl and syringyl units)were detected by Fourier transform infrared spectrometry.Additionally,the higher O/C ratio measured by elemental analysis also confirmed that alkali lignin was depolymerized effectively under mild conditions.
基金This work was supported by the International S＆T Cooperation Program of China （2015DFA00960）, the National Natural Science Foundation of China （Grant Nos. 31600052 and 21676192） and Innovative Talents and Platform Program of Tianjin （16PTSYJC00050）.
文摘The conversion of r-carotene to astaxanthin is a complex pathway network, in which two steps of hydroxylation and two steps ofketolation are catalyzed by β-carotene hydroxylase （CrtZ） and β-carotene ketolase （CrtW） respectively. Here, astaxanthin biosynthesis path- way was constructed in Saccharomyces cerevisiae by introducing heterologous CrtZ and CrtW into an existing high r-carotene producing strain. Both genes crtZ and crtW were codon optimized and expressed under the control of constitutive promoters. Through combinatorial expression of CrtZ and CrtW from diverse species, nine strains in dark red were visually chosen from thirty combinations. In all the selected strains, strain SyBE Scl 18060 with CrtW from Brevundimonas vesicu- laris DC263 and CrtZ from Alcaligenes sp. strain PC-1 achieved the highest astaxanthin yield of 3.1 mg/g DCW. Protein phylogenetic analysis shows that the shorter evolutionary distance of CrtW is, the higher astaxanthin titer is. Further, when the promoter of crtZ in strain SyBE_Scl 18060 was replaced from FBAlp to TEFlp, the astaxanthin yield was increased by 30.4% （from 3.4 to 4.5 mg/g DCW）. In the meanwhile, 33.5-fold increase on crtZ transcription level and 39.1-fold enhancement on the transcriptional ratio of crtZ to crtWwere observed at early exponential phase in medium with 4% （w/v） glucose. Otherwise, although the ratio of crtZ to crtW were increased at mid-, late-exponential phases in medium with 2% （w/v） glucose, the transcription level of both crtZ and crtW were actually decreased during the whole timecourse, consequently leading to no significant improve- ment on astaxanthin production. Finally, through high cell density fed-batch fermentation using a carbon source restriction strategy, the production of astaxanthin in a 5-L bioreactor reached to 81.0 mg/L, which was the highest astaxanthin titer reported in yeast. This study provides a reference to greatly enhance lation by employing the key desired compounds accumu- enzyme（s） in microbes.
