Improving the performance of enzymes in hydrolysis of high solids paper pulp derived from MSW

Abstract

BackgroundThe research aimed to improve the overall conversion efficiency of the CTec® family of enzymes by identifying factors that lead to inhibition and seeking methods to overcome these through process modification and manipulation. The starting material was pulp derived from municipal solid waste and processed in an industrial-scale washing plant.ResultsAnalysis of the pulp by acid hydrolysis showed a ratio of 55 : 12 : 6 : 24 : 3 of glucan : xylan : araban/galactan/mannan : lignin : ash. At high total solids content (>18.5% TS) single-stage enzyme hydrolysis gave a maximum glucan conversion of 68%. It was found that two-stage hydrolysis could give higher conversion if sugar inhibition was removed by an intermediate fermentation step between hydrolysis stages. This, however, was not as effective as direct removal of the sugar products, including xylose, by washing of the residual pulp at pH 5. This improved the water availability and allowed reactivation of the pulp-bound enzymes. Inhibition of enzyme activity could further be alleviated by replenishment of β-glucosidase which was shown to be removed during the wash step.ConclusionsThe two-stage hydrolysis process developed could give an overall glucan conversion of 88%, with an average glucose concentration close to 8% in 4 days, thus providing an ideal starting point for ethanol fermentation with a likely yield of 4 wt%. This is a significant improvement over a single-step process. This hydrolysis configuration also provides the potential to recover the sugars associated with residual solids which are diluted when washing hydrolysed pulp.

Macroalgae-Derived Biofuel: A Review of Methods of Energy Extraction from Seaweed Biomass

“…Cellulosic ethanol was expected to play a large role in meeting the goals of the U.S. Energy Independence and Security Act of 2007 for renewable biofuels [135]; but despite extensive research and the availability of low cost lignocellulosic biomass there is, as yet, no large-scale commercial production of fuel bioethanol from lignocellulosic materials [134,136]. One of the problems encountered with production of bioethanol from straw is that biodegradation of hemicelluloses and cellulose by cellulases can be inhibited by lignin, found in many terrestrial sources of second generation biofuel biomass [137].…”

Effect of Commercial Cellulase Enzymes on Ethanol Production from Pretreated Rice Straw at High Solid Loading

“…High viscosity of slurry is cause to many problems, including insufficient mixing and heat transfer [2,4], shear inactivation of cellulase, decrease in water availability, irreversible blinding of adsorbed enzymes to substrate and enzyme denaturation. There may also be other reasons, as yet unidentified, for decreased conversion [1]. Whereas, unsuitable temperature of cellulase enzymatic hydrolysis will supplement the difficulty of hydrolysing substrate to fermentable sugar.…”

“…To make cellulosic ethanol production be achieved in industrials scales and can be competed with fossil fuel, it requires low cost of conversing lignocellulose to ethanol, which demands not only high yield of ethanol but also high ethanol concentration in the fermentation broth to reduce distillation energy cost [1]. A way of achieving this is the increase of substrate concentration in the slurry [2,3].…”

Avaliação Do Efeito Da Carga De Sólidos Sobre a Hidrólise Enzimática Do Bagaço De Cana-De-Açúcar E Comparação Entre Complexos Enzimáticos Comerciais

“…O aumento da carga de substrato é importante a fim de se obter concentrações mais elevadas de açúcares no hidrolisado (Wang et al, 2012;Puri et al, 2013). Esse fator é importante para se obter na etapa de fermentação vinhos com maior teor de etanol, o que reduz o consumo de energia na etapa de destilação (Modenbach e Nokes, 2013).…”

“…Esse efeito pode ser explicado por fatores como, dificuldade em se homogeneizar a mistura, inibição da enzima com o aumento da concentração de glicose, problemas de transferência de massa, diminuição da disponibilidade de água, ligação irreversível da enzima ao substrato incluindo a ligação não produtiva com a lignina e desnaturação da enzima (Puri et al, 2013).…”