Lignocellulosic ethanol production at high-gravity: challenges and perspectives

Koppram, Rakesh; Tomás‐Pejó, Elia; Xiros, Charilaos; Olsson, Lisbeth

doi:10.1016/j.tibtech.2013.10.003

Cited by 315 publications

(196 citation statements)

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“…Modification of substrate is a common practice to increase the accessibility of the substrate to microorganisms [54,55]. In a previous study, it was found that acid modification of wheat straw significantly enhanced cellulase production in SFF by A. niger [13] v. However, a negative impact of pre-treatment on cellulase production has also Figure 4: Impact of additional carbon, nitrogen or clay on cellulose production.…”

Section: Effect Of Pretreating Msw On Cellulase Productionmentioning

confidence: 99%

Optimizing Cellulase Production from Municipal Solid Waste (MSW) using Solid State Fermentation (SSF)

Abdullah

Greetham

Pensupa

et al. 2016

J Fundam Renewable Energy

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This paper explores the possibility of using an industrially processed municipal solid waste (MSW) for cellulase enzyme production via solid state fermentation (SSF) by Trichoderma reesei and Aspergillus niger. Both fungi grew well on the MSW substrate and production of cellulase enzymes was optimized for temperature, moisture content, inoculation and period of incubation. The effect of additional minerals, and alternative carbon and nitrogen sources were also examined.Following optimization a cellulase activity of 26.10 ± 3.09 FPU/g could be produced using T. reesei at 30°C with a moisture content of 60% with an inoculums of 0.5 million spores/g and incubation for 168 hours. Addition of extra nitrogen and/or carbon did not improve cellulase accumulation. Acid or alkali pretreatment of MSW led to reduced cellulase production. Crude enzymes produced from MSW by T. reesei were evaluated for their ability to release glucose from MSW. A cellulose hydrolysis yield of 24.7% was achieved, which was close to that obtained using a commercial enzyme. Results demonstrated that MSW can be used as an inexpensive lignocellulosic material for the production of cellulase enzymes. Research has revealed that T. reesei can produce 13.4 FPU/g cellulase activity using water hyacinth [8]; 154.58 FPU/g using sugar cane bagasse [10]; 8.2 FPU/g using oil palm empty fruit bunches [11]; and 1.16 FPU/g using rice bran [12] as substrates. Similarly it has been reported that A. Niger could produce 24 FPU/g cellulase activity using wheat straw as a substrate [13]. Other substrates such as banana peel, rice straw, corn cob residue, rice husk, banana fruit stalk, and coconut coir pith have all being used for cellulase production [14,15]. Optimizing Cellulase Production fromAlthough MSW can contain a high lignocellulosic content, there has been limited research into the use of MSW for cellulase production. Other research demonstrated the possibility of using MSW to produce cellulase via SSF. But by using raw not autoclave MSW [16,17]. In this paper, we report an example of using an industrially processed MSW for cellulase production and then the use of the resulting "cellulase cocktail" for the enzymatic hydrolysis of MSW. Materials and Methods Municipal solid wasteMunicipal solid waste (MSW) was kindly supplied by Wilson Steam Storage Ltd (UK). The MSW had been subjected to commercial steam 15 min, respectively. After autoclaving, samples were neutralized to pH 7.0 using either 1 M NaOH or 1 M H 2 SO 4 as appropriate. The samples were then centrifuged at 5000 rpm (4472 g) for 10 min. The solid fraction (pellet) was rinsed three times by adding distilled water to the pellet and re-centrifuged. The solid fraction was then dried overnight at room temperature. Journal of Fundamentals of Renewable Energy and ApplicationsMicroorganisms: Two filamentous fungi, Trichoderma reesei QM6a and Aspergillus niger N402 were kindly donated by Professor David Archer (University of Nottingham, UK). Procedures for storing and cultivating T. reesei and A. n...

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Section: Effect Of Pretreating Msw On Cellulase Productionmentioning

confidence: 99%

Optimizing Cellulase Production from Municipal Solid Waste (MSW) using Solid State Fermentation (SSF)

Abdullah

Greetham

Pensupa

et al. 2016

J Fundam Renewable Energy

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“…High viscosities, decreased cellulase adsorption, increased inhibitor concentrations, reduced nutrient transfer, osmotic stresses, and limitations in mass transfer also contribute to reduced ethanol productivities at high solids loadings. [16][17][18] Despite some of its shortcomings, SSF offers several key process benefits, which facilitate higher substrate loadings and ethanol titers. Namely, glucose released via enzymatic action does not accumulate but is immediately fermented into ethanol, circumventing end-product inhibition.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous Saccharification and Fermentation of PretreatedEucalyptus grandisUnder High Solids Loading

McIntosh

Palmer

Zhang

et al. 2017

Industrial Biotechnology

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Whole Eucalyptus grandis trees (including bark, branches and leaves) were investigated as a potential feedstock for bioethanol production. To demonstrate and maximize ethanol production, unwashed steam exploded wood chips (SEWC) were used as substrates in high solids load simultaneous saccharification fermentations (SSF) with an industrial Saccharomyces cerevisiae strain (Fali Ò ). Under optimized SSF conditions-20 wt% solids, 60 filter paper units (FPU)/g glucan, and 36°C-ethanol titer and glucan-to-ethanol yields of 56 g/L and 90%, respectively, were achieved. Raising the SSF temperature to 39°C showed no observable benefit in final ethanol titers and/or yields. Addition of 3 wt% polyethylene glycol (PEG) further increased final ethanol titers and yields to 60 g/L and 95%, respectively, at a 30% lower cellulase dosage. Considering the mass balance of the best-performing SSF (20 wt% SEWC, 40 FPU Ctec 2/g glucan, 30 mg PEG/g dry solid at 36°C) process, the maximum ethanol attainable was estimated at 187 kg (85.8% yield) and 299 kg (95% yield) per dry metric ton of original and SEWC biomass, respectively.

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“…However, increasing the solids content creates several practical issues, such as mass transfer limitations and a greater concentration of inhibitors, which can offset the cost savings. The challenges of and the outlook on lignocellulosic ethanol production at high solids concentrations have recently been reviewed [20].…”

Section: Introductionmentioning

confidence: 99%

Combined production of biogas and ethanol at high solids loading from wheat straw impregnated with acetic acid: experimental study and techno-economic evaluation

Joelsson

Dienes

Kovács

et al. 2016

Sustain Chem Process

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Background: Production of ethanol and biogas from acetic acid-impregnated steam-pretreated wheat straw was investigated. The solid fraction after pretreatment was used at high solids concentrations to generate ethanol by simultaneous saccharification and fermentation (SSF). The residual streams were evaluated with regard to biogas production. The experimental results were used to perform a techno-economic evaluation of a biorefinery concerning ethanol, raw biogas, pellet, and electricity production at various solid contents and residence times in the fermentation step. The configurations were also altered to include biogas upgrading to vehicle fuel quality or fermentation of xylose to ethanol. Results:At a water-insoluble solids (WIS) content in the SSF of between 10 and 20 %, the ethanol yields exceeded 80 %, the highest being 86 % at 12.5 % WIS, expressed as % of the theoretical maximum, based on the glucan content in SSF. Anaerobic digestion of wheat straw hydrolysate and stillage yielded 4.8 and 1.0-1.2 g methane/100 g dry straw, respectively, in 7-day experiments. Maximum recovery of overall product was achieved when SSF was run at between 10 and 15 % initial WIS content, for which the product yields from 100 g dry wheat straw were 16.1-16.3 g ethanol, 5.8-6.0 g methane, and 25 g lignin-rich solid residue. The net present value (NPV) was negative at discount rate of 11 % but positive at 5 % discount rate for all configurations. The 20 % WIS configuration with a residence time of 96 h in the fermentation stage attained the highest NPV. The minimum ethanol selling price varied between 0.72 and 0.87 EUR/L ethanol when the biogas was unchanged and it decreased to between 0.46 and 0.60 EUR/L ethanol when the biogas was upgraded to vehicle fuel quality or when xylose was converted to ethanol. Conclusions:According to the techno-economic assessment, a process that is based on the fermentation of only hexoses to ethanol, and production of raw biogas from xylose is not profitable under the economic assumptions including 11 % discount rate in the evaluation. However, the profitability of a plant can be improved by biogas upgrading to vehicle fuel quality or fermentation of xylose to ethanol.

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Lignocellulosic ethanol production at high-gravity: challenges and perspectives

Cited by 315 publications

References 64 publications

Optimizing Cellulase Production from Municipal Solid Waste (MSW) using Solid State Fermentation (SSF)

Optimizing Cellulase Production from Municipal Solid Waste (MSW) using Solid State Fermentation (SSF)

Simultaneous Saccharification and Fermentation of PretreatedEucalyptus grandisUnder High Solids Loading

Combined production of biogas and ethanol at high solids loading from wheat straw impregnated with acetic acid: experimental study and techno-economic evaluation

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