Aqua-ammonia pretreatment of corn stover for enhancing enzymatic saccharification

Aqua-ammonia pretreatment of corn stover was provided in a 1.2 L high pressure reactor with two ammonia:biomass ratios of 1:1(w/w)and 2:1(w/w);at three temperatures:60℃,90℃and 120℃,and two treatment time:5 min and 30 min.Pretreatment with water was used as control.The pretreated samples were saccharified to fermentable sugars by commercial enzymes ACCELERASE 1500(cellulase)and ACCELERASE XC(xylanases).For ammonia:biomass ratio of 1:1,the yield of total fermentable sugar was 87%at 90℃for 30 min treatment.In case of ammonia:biomass ratio of 2:1,fermentable sugar yield increased four fold of that of control.Maximum fermentable sugar yield of 99%was obtained for 2:1 ammonia:biomass ratio,90℃,and 30 min treatment time.The results of this study are very promising for improving fermentable sugar yield from corn stover using smaller amount of ammonia than the ammonia fiber explosion and other pretreatments such as strong acid or alkali pretreatments.However,further optimization is required for reducing pretreatment time.

Ameliorated enzymatic saccharification of corn stover with a novel modified alkali pretreatment

Enzymatic saccharification/hydrolysis is one of the key steps for the bioconversion of lignocelluloses into sustainable biofuels.In this work,corn stover was pretreated with a novel modified alkali process(NaOH+anthraquinone(AQ)+sodium lignosulfonate(SLS)),and then enzymatically hydrolyzed with an enzyme cocktail(cellulase(Celluclast 1.5L),β-glucosidase(Novozyme 188)and xylanase(from thermomyceslanuginosus))in the pH range of 4.0-6.5.It was found that the suitable pH for the enzymatic saccharification process to achieve a high glucan yield was between 4.2 and 5.7,while the appropriate pH to obtain a high xylan yield was in the range of 4.0-4.7.The best pH for the enzymatic saccharification process was found to be 4.4 in terms of the final total sugar yield,as xylanase worked most efficiently in the pH range of 4.0-4.7,under the conditions in the study.The addition of xylanase in the enzymatic saccharification process could hydrolyze xylan in the substrates and reduce the nonspecific binding of cellulase,thus improving the total sugar yields.

Influence of lignin content on enzymatic saccharification of poplar wood chips by different pretreatment methods

Bioconversion of lignocellulose to fermentable sugars is a promising approach to produce potential bio-based energy and chemicals.Pretreatment is the key step to remove or delocalize lignin in lignocellulose,thus improving enzymatic saccharification efficiency.In this study,three kinds of pretreatment methods(ethanol,bisulfite and sulfate)were employed to produce substrates with various lignin contents which were subsequently subjected to biological saccharification processes.Results showed that a lower lignin content led to a higher fermentable sugar yield based on reducing sugar release for all samples.Additionally,the sulfate pretreatment improved the enzymatic saccharification efficiency in a greater extent than the others.Fourier transform infrared(FTIR)spectroscopy confirmed the structure changes during pretreatment.

Oligomer saccharide reduction during dilute acid pretreatment co-catalyzed with Lewis acids on corn stover biomass

The dilute sulfuric acid pretreatment of lignocellulosic biomass is a well understood process that significantly enhances the yield of glucose after enzymatic saccharification.The goal of this research was to perform a systematic study to evaluate the yield of fermentable sugars during dilute sulfuric acid pretreatment that is co-catalyzed with the transition metal Lewis acid salts:AlCl_(3),FeCl_(2),FeCl_(3),and La(OTf)_(3).All Lewis acids apart from FeCl_(2)reduced the presence of xylo-oligomers by a large margin when compared to the non-co-catalyzed control sample pretreatments.The presence of these xylo-oligomers acts as inhibitors during enzymatic saccaharification step.The Lewis acids AlCl_(3),FeCl_(3),and La(OTf)_(3)were also able to marginally increase the overall enzymatic digestibility specifically for corn stover pretreated at 160℃with 10 mM of Lewis acids.The hard Lewis acid such as AlCl3 increased the formation inhibitory products such as furfural and 5-hydroxymethylfurfural(HMF).There was good correlation between reduction of xylo-oligomers and increased concentration furfural with increase in Lewis acid hardness.