Lignin fractionation and depolymerization generates heterogeneous streams of aromatic compounds and conversion of aromatic compounds into valuable products,but it is not efficient.Many microbes in nature have evolved ...Lignin fractionation and depolymerization generates heterogeneous streams of aromatic compounds and conversion of aromatic compounds into valuable products,but it is not efficient.Many microbes in nature have evolved metabolic path-ways to convert complex lignin polymers into aromatic compounds and transform these aromatic compounds into central intermediates for bioproduct synthesis.The objective of this paper is to review the recent process development of lignin bioconversion into aromatic compounds and bioproducts.Lignin structural and molecular changes during fractionation and depolymerization are presented.Subsequent lignin conversion into aromatic compounds by upper pathways and further converted into central metabolites and bioproducts via lower pathways are emphasized.In particular,enzymes and mediator systems to enhance lignin conversion and key intermediates in lignin catabolic pathways are discussed.Strategies to enhance bioproduct formation through lignin valorization are summarized.展开更多
Succinic acid is one of the most useful intermediate chemicals that can be produced in a biorefinery approach.In this study,Actinobacillus succinogenes was immobilized to produce succinic acid using non-detoxified cor...Succinic acid is one of the most useful intermediate chemicals that can be produced in a biorefinery approach.In this study,Actinobacillus succinogenes was immobilized to produce succinic acid using non-detoxified corn fiber hydrolysate(CFH)and a control mimicking the sugars in CFH.Tests were carried out in a hollow fiber membrane packed-bed biofilm reactor(HFM–PBR)operated in a continuous mode.Under steady-state conditions,the bioconversion process was characterized in terms of sugar consumption,succinic acid and other organic acid production.Steady states were obtained at dilution rates of 0.025,0.05,0.075,0.1,0.2,and 0.3 h^(-1).The optimal results were achieved at the dilution rate of 0.05 h^(-1)and recirculation rate of 50 ml/min with a maximum succinic acid concentration,yield and productivity of 31.1 g/L,0.61 g/g and 1.56 g/L h,respectively,when control was used.Succinic acid concentration,yield and productivity of 23.4 g/L,0.51 g/g and 1.17 g/L h,respectively,were obtained when CFH was used.Productivity in the HFM–PBR was between 1.3 and 1.9 times higher than productivities for succinic acid production from CFH stated in the literature.The results demonstrated that immobilized A.succinogenes has the potential for effective conversion of an inexpensive biomass feedstock to succinic acid.Furthermore,the process has the potential to serve as a means for value-added chemical biomanufacturing in an integrated corn biorefinery.展开更多
文摘Lignin fractionation and depolymerization generates heterogeneous streams of aromatic compounds and conversion of aromatic compounds into valuable products,but it is not efficient.Many microbes in nature have evolved metabolic path-ways to convert complex lignin polymers into aromatic compounds and transform these aromatic compounds into central intermediates for bioproduct synthesis.The objective of this paper is to review the recent process development of lignin bioconversion into aromatic compounds and bioproducts.Lignin structural and molecular changes during fractionation and depolymerization are presented.Subsequent lignin conversion into aromatic compounds by upper pathways and further converted into central metabolites and bioproducts via lower pathways are emphasized.In particular,enzymes and mediator systems to enhance lignin conversion and key intermediates in lignin catabolic pathways are discussed.Strategies to enhance bioproduct formation through lignin valorization are summarized.
基金The authors wish to acknowledge the Nebraska Corn Board for funding this work under award number 88-R-1718-01the financial support of the University of Nebraska-Lincoln Agricultural Research Division.
文摘Succinic acid is one of the most useful intermediate chemicals that can be produced in a biorefinery approach.In this study,Actinobacillus succinogenes was immobilized to produce succinic acid using non-detoxified corn fiber hydrolysate(CFH)and a control mimicking the sugars in CFH.Tests were carried out in a hollow fiber membrane packed-bed biofilm reactor(HFM–PBR)operated in a continuous mode.Under steady-state conditions,the bioconversion process was characterized in terms of sugar consumption,succinic acid and other organic acid production.Steady states were obtained at dilution rates of 0.025,0.05,0.075,0.1,0.2,and 0.3 h^(-1).The optimal results were achieved at the dilution rate of 0.05 h^(-1)and recirculation rate of 50 ml/min with a maximum succinic acid concentration,yield and productivity of 31.1 g/L,0.61 g/g and 1.56 g/L h,respectively,when control was used.Succinic acid concentration,yield and productivity of 23.4 g/L,0.51 g/g and 1.17 g/L h,respectively,were obtained when CFH was used.Productivity in the HFM–PBR was between 1.3 and 1.9 times higher than productivities for succinic acid production from CFH stated in the literature.The results demonstrated that immobilized A.succinogenes has the potential for effective conversion of an inexpensive biomass feedstock to succinic acid.Furthermore,the process has the potential to serve as a means for value-added chemical biomanufacturing in an integrated corn biorefinery.
