Separate Hydrolysis And Fermentation Research Articles

Enriching Duckweed As an Energy Crop for Producing Biobutanol Using Enzyme Hydrolysis Pretreatments and Strengthening Fermentation Process Using pH-stat

Large scale production of biobutanol from a lignocellulosic feedstock for alternative fossil fuels consumption has garnered much interest by researchers in renewable energy. However, making biobutanol from lignocellulose requires the development of novel, renewable, nonfood sources for biofuel production and sustainable biorefining technology that maximizes the utilization of feedstock is indispensable. Duckweed (Lemnaceae) is a family of aquatic plants that in early trials has demonstrated great potential as an alternative nonfood energy feedstock for ethanol production. However, research on methods to obtain higher biobutanol yield from this plant is thus far insufficient. In this study, we tested several hydrolysis procedures with different enzyme combinations for duckweed pretreatment in detail. We then assessed the efficiency of these treatments for biobutanol production via fermentation with Clostridium acetobutylicum, using separate hydrolysis and fermentation (SHF) and simultaneous saccharificatio...

Encapsulated yeast cell-free system: A strategy for cost-effective and sustainable production of bio-ethanol in consecutive batches

This study was intended to develop an encapsulated yeast cell-free system (EyCFS) by confining yeast cell-free lysate within a calcium alginate capsule. The system was evaluated for bio-ethanol production at elevated temperatures and was compared to a bare yeast cell-free system (ByCFS). Fermentation of 10 g/L glucose with shaking (150 rpm), using 2 mg/mL cell-free proteins in the ByCFS produced 3.31 g/L bio-ethanol, corresponding to 65% of the maximal theoretical yield, at 45°C and pH 7.0. On the contrary, the EyCFS produced 4.12 g/L bioethanol, corresponding to 81% of the maximal theoretical yield, under the same experimental conditions. The EyCFS also retained 32% of its original activity after 15 consecutive batches. We observed an 11% increase in bio-ethanol production after replenishment of cofactors (ATP and NADH) and ATPase. The weight-based total turnover number (TTNw; 0.82 × 103), cost ratio (R value; 1.22), and yield (80.4%) indicated the economic suitability of the EyCFS for large-scale production. Connecting the EyCFS with an encapsulated saccharification system through separate hydrolysis and fermentation (SHF) resulted in production of 4.87 g/L bio-ethanol, corresponding to 87.6% of the maximal theoretical yield. This system resolved serious limitations of conventional simultaneous saccharification and fermentation in bare cell-free systems. These data demonstrates the superiority of the proposed system in terms of thermal stability, yield, efficacy, and cost-effectiveness.

Utilization of recombinant Trichoderma reesei expressing Aspergillus aculeatus β-glucosidase I (JN11) for a more economical production of ethanol from lignocellulosic biomass

The capacity of Trichoderma reesei cellulase to degrade lignocellulosic biomass has been enhanced by the construction of a recombinant T.reesei strain expressing Aspergillus aculeatus β-glucosidase I. We have confirmed highly efficient ethanol production from converge-milled Japanese cedar by recombinant T.reesei expressing A.aculeatus β-glucosidase I (JN11). We investigated the ethanol productivity of JN11 and compared it with the cocktail enzyme T.reesei PC-3-7 with reinforced cellobiase activity by the commercial Novozyme 188. Results showed that the ethanol production efficiency under enzymatic hydrolysis of JN11 was comparable to the cocktail enzyme both on simultaneous saccharification and fermentation (SSF) or separate hydrolysis and fermentation (SHF) processes. Moreover, the cocktail enzyme required more protein loading for attaining similar levels of ethanol conversion as JN11. We propose that JN11 is an intrinsically economical enzyme that can eliminate the supplementation of BGL for PC-3-7, thereby reducing the cost of industrial ethanol production from lignocellulosic biomass.

Feasibility of acetone–butanol–ethanol (ABE) fermentation from Amorphophallus konjac waste by Clostridium acetobutylicum ATCC 824

Using Amorphophallus konjac waste as a source of fermentable carbohydrate, the feasibility of acetone–butanol–ethanol (ABE) fermentation by Clostridium acetobutylicum ATCC 824 was investigated in this study. Two distinct combination strategies for the enzymatic hydrolysis and fermentation, simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF), for konjac waste fermentation were compared. β-Mannanase was added to facilitate the hydrolysis of glucomannan and to increase the fermentability of the substrate. The ABE concentration (6.64g/L) from SSF was less than that from SHF; the result from the control experiment was 4.34g/L of ABE. SHF obtained a higher production of total ABE solvents (10.95g/L) with 7.10g/L of butanol at a productivity rate of 0.30g/L/h. The effect of the bioactive alkaloid abundant in the konjac waste on ABE fermentation was evaluated. The results indicated that the alkaloid affected the ABE fermentation results when using C. acetobutylicum, and the effective extraction of alkaloids can help to increase the butanol concentration and shorten the fermentation period. Therefore, the utilization of Amorphophallus konjac waste (a low-cost agricultural resource) in ABE fermentation provides an alternative to increase the economic viability of ABE production.

Hierarchical economic potential approach for techno-economic evaluation of bioethanol production from palm empty fruit bunches

A hierarchical four-level approach to determine economic potential (4-level EP) is proposed for preliminary techno-economic analysis of new processes. The 4-level EP includes input/output structure, process flow structure, heat integration (HI), and economic feasibility. Two case studies on a 30.2t/d (or 12.7million l/yr) bioethanol plant with and without jet fuel production from palm empty fruit bunches (EFB) were investigated by applying the 4-level EP. The plant flowsheet was established based on experiments in a 0.1t/d pilot plant, including sequential dilute acid and alkali pretreatment, and separate hydrolysis and fermentation (SHF). EP approached a more reliable value through the hierarchical 4-level EP. The heating energy was reduced considerably by HI. The product value was estimated at $0.8–$1.3/kg of equivalent bioethanol. It was suggested through sensitivity analysis that a large plant size, enhanced production yields, and capital cost reduction were necessary for the lignocellulosic bioethanol production to be profitable.

Comparison of SHF and SSF Processes Using Enzyme and Dry Yeast for Optimization of Bioethanol Production from Empty Fruit Bunch

Abstract Empty fruit bunch was considered as substrate for second generation of bioethanol because it consists of lignin, cellulose, and hemicelluloses. For lignocelluloses materials, it usually needs pretreatment and hydrolysis to convert cellulose into glucose. Two methods of enzymatic hydrolysis, Separated Hydrolysis and Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) were carried out in this study. The performance of both SHF and SSF was concerned to evaluate the effect of hydrolysis methods and enzyme concentration for producing ethanol. Pretreatment was conducted in a reactor using 10% sodium hydroxide at temperature 150 °C during 30 minutes. Two kinds of enzyme, Cellic® CTec2 and Cellic® HTec2 from novozyme were added in 15% (gr/ml) of pretreated EFB at pH 4.8. Four concentration of enzyme Cellic® CTec2, 10, 20, 30, 40 FPU per gram biomass were performed in SHF and SSF processes respectively, while Cellic® HTec2 was added 20% from Cellic® CTec2. Contents of glucose, xylose, and ethanol were recorded every 24 hours. Using 40 FPU of concentration enzyme, it could be produce 4.74% of ethanol in 72 hours fermentation by SHF process and 6.05% of ethanol in 24 hours by SSF process. From this study, the SSF method was considered as a better process than SHF due to rapidly ethanol production and the highest concentration of produced ethanol.

Thermal Acid Hydrolysis Pretreatment, Enzymatic Saccharification and Ethanol Fermentation from Red Seaweed, Gracilaria verrucosa

In this study, the red seaweed Gracilaria verrucosa was used as a bioethanol producing biomass. G. verrocosa has a high content of easily degradable carbohydrates, making it a potential substrate for the production of liquid fuels [8]. The carbohydrates in G. verrucosa can be categorised according to their chemical structures: alginate, carrageenan, and agar. Carrageenan and agar, which are plentiful in the seaweed, can be used as a source of galactose and glucose. Various pretreatment techniques have been introduced to enhance the overall hydrolysis yield, and can be categorized into physical, chemical, biological, enzymatic or a combination of these [1]. Dilute acid hydrolysis is commonly used to prepare seaweed hydrolysates for enzymatic saccharification and fermentation for economic reasons [13]. However, thermal acid hydrolysis pretreatment for 3,6anhydrogalactose from G. verrucosa have produced 5hydroxymethylfurfural (HMF), an inhibitory compound for ethanol production [8]. One of the problems encountered in G. verrucosa fermentation has been high concentrations of NaCl due to its origin from sea water [3]. High-salt stress to yeasts is a significant impediment on the production of ethanol from seaweed hydrolysates. Salt stress in yeasts results in two phenomena: ion toxicity and osmotic stress [11]. Defense responses to salt stress are based on osmotic adjustments by osmolyte synthesis and cation transport systems for sodium exclusion [20]. The preferential utilization of glucose over non-glucose sugars by yeast often results in low overall ethanol production and yield. When yeast grows on a mixture of glucose and galactose, the glucose is metabolized first, whereas The seaweed, Gracilaria verrucosa, was fermented to produce bioethanol. Optimal pretreatment conditions were determined to be 12% (w/v) seaweed slurry and 270 mM sulfuric acid at 121C for 60 min. After thermal acid hydrolysis, enzymatic saccharification was carried out with 16 U/ml of mixed enzymes using Viscozyme L and Celluclast 1.5 L to G. verrucosa hydrolysates. A total monosaccharide concentration of 50.4 g/l, representing 84.2% conversion of 60 g/l total carbohydrate from 120 g dw/l G. verrucosa slurry was obtained by thermal acid hydrolysis and enzymatic saccharification. G. verrucosa hydrolysate was used as the substrate for ethanol production by separate hydrolysis and fermentation (SHF). Ethanol production by Candida lusitaniae ATCC 42720 acclimated to high-galactose concentrations was 22.0 g/l with ethanol yield (YEtOH) of 0.43. Acclimated yeast to high concentrations of specific sugar could utilize mixed sugars, resulting in higher ethanol yields in the seaweed hydrolysates medium.

Enzymatic saccharification and bioethanol production from Cynara cardunculus pretreated by steam explosion

The correct choice of the specific lignocellulosic biomass pretreatment allows obtaining high biomass conversions for biorefinery implementations and cellulosic bioethanol production from renewable resources. Cynara cardunculus (cardoon) pretreated by steam explosion (SE) was involved in second-generation bioethanol production using separate hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF) processes. Steam explosion pretreatment led to partial solubilisation of hemicelluloses and increased the accessibility of residual polysaccharides towards enzymatic hydrolysis revealing 64% of sugars yield against 11% from untreated plant material. Alkaline extraction after SE pretreatment of cardoon (CSEOH) promoted partial removal of degraded lignin, tannins, extractives and hemicelluloses thus allowing to double glucose concentration upon saccharification step. Bioethanol fermentation in SSF mode was faster than SHF process providing the best results: ethanol concentration 18.7gL−1, fermentation efficiency of 66.6% and a yield of 26.6g ethanol/100g CSEOH or 10.1g ethanol/100g untreated cardoon.

A comparison between SHF and SSSF processes from cardoon for ethanol production

The purpose of the present work is the evaluation of Cynara cardunculus L. potential in terms of ethanol production from lignocellulosic feedstock for industrial purposes. After a steam explosion (SE) pretreatment at different severity conditions, to obtain the dissolution of hemicellulose and the separation between cellulose and lignin, two different processes were tested: separate hydrolysis and fermentation (SHF) and semi-simultaneous saccharification and fermentation (SSSF). The enzymatic hydrolysis was carried out with ™Ctec2 cellulase enzyme and fermentation with Saccharomyces cerevisiae yeast.The results showed slightly better performances by SSSF process compared to SHF, especially at low severity conditions, with a maximum overall ethanol yield of 13.64g of ethanol/100g of raw material. For the SHF process the best overall ethanol yield achieved was 13.17g of ethanol/100g of raw materials. In addition, the SSSF process required at least 24h less than the SHF to achieve the same final ethanol concentration for every severity condition tested.

Phenyllactic acid production by simultaneous saccharification and fermentation of pretreated sorghum bagasse

Dilute acid-pretreated sorghum bagasse, which was predominantly composed of glucan (59%) and xylose (7.2%), was used as a lignocellulosic feedstock for d-phenyllactic acid (PhLA) production by a recombinant Escherichia coli strain expressing phenylpyruvate reductase from Wickerhamia fluorescens. During fermentation with enzymatic hydrolysate of sorghum bagasse as a carbon source, the PhLA yield was reduced by 35% compared to filter paper hydrolysate, and metabolomics analysis revealed that NAD(P)H regeneration and intracellular levels of erythrose-4-phosphate and phosphoenolpyruvate for PhLA biosynthesis markedly reduced. Compared to separate hydrolysis and fermentation (SHF) with sorghum bagasse hydrolysate, simultaneous saccharification and fermentation (SSF) of sorghum bagasse under glucose limitation conditions yielded 4.8-fold more PhLA with less accumulation of eluted components, including p-coumaric acid and aldehydes, which inhibited PhLA fermentation. These results suggest that gradual enzymatic hydrolysis during SSF enhances PhLA production under glucose limitation and reduces the accumulation of fermentation inhibitors, collectively leading to increased PhLA yield.

Influence of bark on fuel ethanol production from steam-pretreated spruce.

BackgroundBark and bark-containing forest residues have the potential for utilization as raw material for lignocellulosic ethanol production due to their abundance and low cost. However, the different physical properties and chemical composition of bark compared to the conventionally used wood chips may influence the spruce-to-ethanol bioconversion process. This study assesses the impact of bark on the overall bioconversion in two process configurations, separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF), utilizing steam-pretreated spruce bark and wood mixtures.ResultsMixtures of different proportions of spruce bark and wood chips were subjected to SO2-catalyzed steam pretreatment at 210°C for five minutes, which has been shown to be effective for the pretreatment of spruce wood chips. The final ethanol concentration was the highest without bark and decreased significantly with increasing proportions of bark in both process configurations. However, this decrease cannot be attributed solely to the lower availability of the carbohydrates in mixtures containing bark, as the ethanol yield also decreased, from 85 to 59% in SSF and from 84 to 51% in SHF, as the mass fraction of bark was increased from 0 to 100%.ConclusionsThe results show that it was significantly more difficult to hydrolyse spruce bark to monomeric sugars than wood chips. Bark had an adverse effect on the whole bioconversion process due to its lower enzymatic hydrolyzability. On the other hand, bark inclusion had no detrimental effect on the fermentability of steam-pretreated spruce wood and bark mixtures. It was also observed that lower amounts of inhibitory degradation products were formed during the steam pretreatment of spruce bark than during the steam pretreatment of wood chips.

Enhanced enzymatic hydrolysis and ethanol production from cashew apple bagasse pretreated with alkaline hydrogen peroxide

The effect of combinations and ratios between different enzymes has been investigated in order to assess the optimal conditions for hydrolysis of cashew apple bagasse pretreated with alkaline hydrogen peroxide (the solids named CAB-AHP). The separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes were evaluated in the ethanol production. The enzymatic hydrolysis conducted with cellulase complex and β-glucosidase in a ratio of 0.61:0.39, enzyme loading of 30FPU/gCAB-AHP and 66CBU/gCAB-AHP, respectively, using 4% cellulose from CAB-AHP, turned out to be the most effective conditions, with glucose and xylose yields of 511.68mg/gCAB-AHP and 237.8mg/gCAB-AHP, respectively. Fermentation of the pure hydrolysate by Kluyveromyces marxianus ATCC 36907 led to an ethanol yield of 61.8kg/tonCAB, corresponding to 15g/L ethanol and productivity of 3.75g/(Lh). The ethanol production obtained for SSF process using K. marxianus ATCC 36907 was 18g/L corresponding to 80% yield and 74.2kg/tonCAB.

Sustaining ethanol production from lime pretreated water hyacinth biomass using mono and co-cultures of isolated fungal strains with Pichia stipitis

Background: The high rate of propagation and easy availability of water hyacinth has made it a renewable carbon source for biofuel production. The present study was undertaken to screen the feasibility of using water hyacinth's hemicelluloses as a substrate for alcohol production by microbial fermentation using mono and co-cultures of Trichoderma reesei and Fusarium oxysporum with Pichia stipitis. Results: In separate hydrolysis and fermentation (SHF), the alkali pretreated water hyacinth biomass was saccharified by crude fungal enzymes of T. reesei, F. oxysporum and then fermented by P. stipitis. In simultaneous saccharification and fermentation (SSF), the saccharification and fermentation was carried out simultaneously at optimized conditions using mono and co-cultures of selected fungal strains. Finally, the ethanol production kinetics were analyzed by appropriate methods. The higher crystalline index (66.7%) and the Fourier transform infrared (FTIR) spectra showed that the lime pretreatment possibly increased the availability of cellulose and hemicelluloses for enzymatic conversion. In SSF, the co-culture fermentation using T. reesei and P. stipitis was found to be promising with a higher yield of ethanol (0.411 g g �1 ) at 60 h. The additional yield comparable with the monocultures was due to the xylanolytic activity of P. stipitis which ferments pentose sugars into ethanol. In SHF, the pretreatment followed by crude enzymatic hydrolysis and fermentation resulted in a significantly lesser yield of ethanol (0.344 g g �1 )a t 96 h. Conclusions: It is evident from the study that the higher ethanol production was attained in a shorter period in the co-culture system containing T. reesei and the xylose fermenting yeast P. stipitis. SSF of pretreated water hyacinth biomass (WHB) with P. stipitis instead of traditional yeast is found to be an effective biofuel production process.

Simultaneous saccharification and fermentation of steam-exploded corn stover at high glucan loading and high temperature.

BackgroundSimultaneous saccharification and fermentation (SSF) is a promising process for bioconversion of lignocellulosic biomass. High glucan loading for hydrolysis and fermentation is an efficient approach to reduce the capital costs for bio-based products production. The SSF of steam-exploded corn stover (SECS) for ethanol production at high glucan loading and high temperature was investigated in this study.ResultsGlucan conversion of corn stover biomass pretreated by steam explosion was maintained at approximately 71 to 79% at an enzyme loading of 30 filter paper units (FPU)/g glucan, and 74 to 82% at an enzyme loading of 60 FPU/g glucan, with glucan loading varying from 3 to 12%. Glucan conversion decreased obviously with glucan loading beyond 15%. The results indicated that the mixture was most efficient in enzymatic hydrolysis of SECS at 3 to 12% glucan loading. The optimal SSF conditions of SECS using a novel Saccharomyces cerevisiae were inoculation optical density (OD)600 = 4.0, initial pH 4.8, 50% nutrients added, 36 hours pre-hydrolysis time, 39°C, and 12% glucan loading (20% solid loading). With the addition of 2% Tween 20, glucan conversion, ethanol yield, final ethanol concentration reached 78.6%, 77.2%, and 59.8 g/L, respectively, under the optimal conditions. The results suggested that the solid and degradation products’ inhibitory effect on the hydrolysis and fermentation of SECS were also not obvious at high glucan loading. Additionally, glucan conversion and final ethanol concentration in SSF of SECS increased by 13.6% and 18.7%, respectively, compared with separate hydrolysis and fermentation (SHF).ConclusionsOur research suggested that high glucan loading (6 to 12% glucan loading) and high temperature (39°C) significantly improved the SSF performance of SECS using a thermal- and ethanol-tolerant strain of S. cerevisiae due to the removal of degradation products, sugar feedback, and solid’s inhibitory effects. Furthermore, the surfactant addition obviously increased ethanol yield in SSF process of SECS.

Conversion of cellulosic materials into glycolipid biosurfactants, mannosylerythritol lipids, by Pseudozyma spp. under SHF and SSF processes.

BackgroundMannosylerythritol lipids (MEL) are glycolipids with unique biosurfactant properties and are produced by Pseudozyma spp. from different substrates, preferably vegetable oils, but also sugars, glycerol or hydrocarbons. However, solvent intensive downstream processing and the relatively high prices of raw materials currently used for MEL production are drawbacks in its sustainable commercial deployment. The present work aims to demonstrate MEL production from cellulosic materials and investigate the requirements and consequences of combining commercial cellulolytic enzymes and Pseudozyma spp. under separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) processes.ResultsMEL was produced from cellulosic substrates, Avicel® as reference (>99% cellulose) and hydrothermally pretreated wheat straw, using commercial cellulolytic enzymes (Celluclast 1.5 L® and Novozyme 188®) and Pseudozyma antarctica PYCC 5048T or Pseudozyma aphidis PYCC 5535T. The strategies included SHF, SSF and fed-batch SSF with pre-hydrolysis. While SSF was isothermal at 28°C, in SHF and fed-batch SSF, yeast fermentation was preceded by an enzymatic (pre-)hydrolysis step at 50°C for 48 h. Pseudozyma antarctica showed the highest MEL yields from both cellulosic substrates, reaching titres of 4.0 and 1.4 g/l by SHF of Avicel® and wheat straw (40 g/l glucan), respectively, using enzymes at low dosage (3.6 and 8.5 FPU/gglucan at 28°C and 50°C, respectively) with prior dialysis. Higher MEL titres were obtained by fed-batch SSF with pre-hydrolysis, reaching 4.5 and 2.5 g/l from Avicel® and wheat straw (80 g/l glucan), respectively.ConclusionsThis work reports for the first time MEL production from cellulosic materials. The process was successfully performed through SHF, SSF or Fed-batch SSF, requiring, for maximal performance, dialysed commercial cellulolytic enzymes. The use of inexpensive lignocellulosic substrates associated to straightforward downstream processing from sugary broths is expected to have a great impact in the economy of MEL production for the biosurfactant market, inasmuch as low enzyme dosage is sufficient for good systems performance.

Direct utilization of kitchen waste for bioethanol production by separate hydrolysis and fermentation (SHF) using locally isolated yeast

ABSTRACTKitchen wastes containing high amounts of carbohydrates have potential as low-cost substrates for fermentable sugar production. In this study, enzymatic saccharification of kitchen waste was carried out. Response surface methodology (RSM) was applied to optimize the enzymatic saccharification conditions of kitchen waste. This paper presents analysis of RSM in a predictive model of the combined effects of independent variables (pH, temperature, glucoamylase activity, kitchen waste loading, and hydrolysis time) as the most significant parameters for fermentable sugar production and degree of saccharification. A 100 mL of kitchen waste was hydrolyzed in 250 mL of shake flasks. Quadratic RSM predicted maximum fermentable sugar production of 62.79 g/L and degree of saccharification (59.90%) at the following optimal conditions: pH 5, temperature 60°C, glucoamylase activity of 85 U/mL, and utilized 60 g/L of kitchen waste as a substrate at 10 h hydrolysis time. The verification experiments successfully produced 62.71 ± 0.7 g/L of fermentable sugar with 54.93 ± 0.4% degree of saccharification within 10 h of incubation, indicating that the developed model was successfully used to predict fermentable sugar production at more than 90% accuracy. The sugars produced after hydrolysis of kitchen waste were mainly attributed to monosaccharide: glucose (80%) and fructose (20%). The fermentable sugars obtained were subsequently used as carbon source for bioethanol production by locally isolated yeasts: Saccharomyces cerevisiae, Candida parasilosis, and Lanchancea fermentati. The yeasts were successfully consumed as sugars hydrolysate, and produced the highest ethanol yield ranging from 0.45 to 0.5 g/g and productivity between 0.44 g L–1 h–1 and 0.47 g L–1 h–1 after 24-h incubation, which was equivalent to 82.06–98.19% of conversion based on theoretical yield.

Using recombinant cyanobacterium (Synechococcus elongatus) with increased carbohydrate productivity as feedstock for bioethanol production via separate hydrolysis and fermentation process

In this work, a recombinant cyanobacterium strain with increased photosynthesis rate, cell growth and carbohydrate production efficiency was genetically engineered by co-expressing ictB, ecaA, and acsAB (encoded for bacterial cellulose) in Synechococcus elongatus PCC7942. The resulting cyanobacterial biomass could be effectively hydrolyzed with dilute acid (2% sulfuric acid), achieving a nearly 90% glucose recovery at a biomass concentration of 80g/L. Bioethanol can be produced from fermenting the acidic hydrolysate of S. elongatus PCC7942 via separate hydrolysis and fermentation (SHF) process at a concentration of 7.2g/L and with a 91% theoretical yield.

Enhanced Enzymatic Hydrolysis of Waste Paper for Ethanol Production Using Separate Saccharification and Fermentation

Ethanol produced from lignocellulosic biomass is a renewable alternative to diminishing petroleum-based liquid fuels. In this study, the feasibility of ethanol production from waste paper using the separate hydrolysis and fermentation (SHF) was investigated. Two types of waste paper materials, newspaper and office paper, were evaluated for their potential to be used as a renewable feedstock for the production of fermentable sugars via enzymatic hydrolysis of their cellulose fractions. Hydrolysis step was conducted with a mixture of cellulolytic enzymes produced locally by Trichoderma reesei Rut-C30 (cellulase-overproducing mutant) and Aspergillus niger F38 cultures. Surfactant pretreatment effect on waste paper enzymatic digestibility was studied and Triton X-100 at 0.5 % (w w(-1)) has improved the digestibility of newspaper about 45 %. The effects of three factors (dry matter quantity, phosphoric acid pretreatment and hydrolysis time) on the extent of saccharification were also assessed and quantified by using a methodical approach based on response surface methodology. Under optimal hydrolysis conditions, maximum degrees of saccharification of newspaper and office paper were 67 and 92 %, respectively. Sugars released from waste paper were subsequently converted into ethanol (0.38 g ethanol g(-1) sugar) with Saccharomyces cerevisiae CTM-30101.

Acetone–butanol–ethanol production by separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) methods using acorns and wood chips of Quercus acutissima as a carbon source

We investigated the production of acetone–butanol–ethanol (ABE) from acorns (starchy material) and wood chips (cellulosic material) of Quercus acutissima through separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) by Clostridium acetobutylicum NBRC13948. With acorns, 15.45g/L of ABE was obtained in 96h of fermentation time from the enzymatic hydrolyzate of acorns by SHF. From the SSF, it was found that ABE (16.70g/L, 120h) was produced without enzyme addition, given that C. acetobutylicum NBRC 13948 possesses an amylolytic enzyme. With wood chips, steam explosion was used for pretreatment. In the SHF, when the enzymatic hydrolyzate of residue of water and methanol extraction after pretreatment was used as the substrate, the maximum ABE concentration, 15.29g/L, was obtained in 120h. From the SSF, 13.41g/L of ABE was obtained in 144h, and it was determined that sufficient enzyme loading was 7.8mg of protein to 1g of dry substrate.

Effect of initial particle size and densification on AFEX-pretreated biomass for ethanol production.

Switchgrass (SG), corn stover (CS), and prairie cordgrass (PCG) pretreated with ammonia fiber expansion (AFEX) were densified using a novel low-temperature, low-pressure densification method. Simultaneous saccharification and fermentation (SSF) and separate hydrolysis and fermentation (SHF) were performed with loose and densified AFEX-treated biomass to determine the effect of post-AFEX densification. Biomass particle size reduction before pretreatment increased 144-h SSF ethanol yields from densified material by 8-9 % although no significant differences were seen in the first 72 h. Grinding material after densification had no impact on final ethanol yields but increased production rates in the first 24-48 h. Low-pressure, post-AFEX densification had no adverse effects on SSF ethanol yields from SG or CS but reduced yields from densified PCG by 16 %. Glucose concentrations after hydrolysis (SHF) showed similar trends. Ethanol yields after SHF, however, showed that densification had no significant impact on CS or PCG but reduced final ethanol yields from SG.