Enzymatic Hydrolysis and Fermentation of Pretreated Cashew Apple Bagasse with Alkali and Diluted Sulfuric Acid for Bioethanol Production

The aim of this work was to optimize the enzymatic hydrolysis of the cellulose fraction of cashew apple bagasse (CAB) after diluted acid (CAB-H) and alkali pretreatment (CAB-OH), and to evaluate its fermentation to ethanol using Saccharomyces cerevisiae. Glucose conversion of 82?±?2 mg/g CAB-H and 730?±?20 mg/g CAB-OH was obtained when 2% (w/v) of solid and 30 FPU/g bagasse was used during hydrolysis at 45 °C, 2-fold higher than when using 15 FPU/g bagasse, 44?±?2 mg/g CAB-H, and 450?±?50 mg/g CAB-OH, respectively. Ethanol concentration and productivity, achieved after 6 h of fermentation, were 20.0?±?0.2 g L^?1 and 3.33 g L^?1 h^?1, respectively, when using CAB-OH hydrolyzate (initial glucose concentration of 52.4 g L^?1). For CAB-H hydrolyzate (initial glucose concentration of 17.4 g L^?1), ethanol concentration and productivity were 8.2?±?0.1 g L^?1 and 2.7 g L^?1 h^?1 in 3 h, respectively. Hydrolyzates fermentation resulted in an ethanol yield of 0.38 and 0.47 g/g glucose with pretreated CAB-OH and CAB-H, respectively. Ethanol concentration and productivity, obtained using CAB-OH hydrolyzate, were close to the values obtained in the conventional ethanol fermentation of cashew apple juice or sugar cane juice.     

Optimization of Saccharification and Fermentation Process in Bioethanol Production from Oil Palm Fronds

Oil Palm Frond (OPF) is one of lignocellulosic biomass, which can be utilized as raw material for bioethanol production. Bioethanol is produced as alternative energy to substitute gasoline. There are four steps in bioethanol production from OPF, i.e pretreatement, saccharification, fermentation and purification process. In this study, optimization of saccharification and fermentation process for OPF was investigated. Two methods and the variations of enzyme concentration were carried out in the saccharification and fermentation process. Separate hydrolysis and fermentation process (SHF) and simultaneous saccharification and fermentation process (SSF) were conducted to produce ethanol optimally. Variations of enzyme concentration used in this process were 10, 20, 30 and 40 FPU/g substrate. The result shows that the highest ethanol concentration can be obtained in SSF process with 30 FPU/g substrate of enzyme concentration. The process produced 59.20 g/L ethanol (95.95% yield ethanol) at 96 h of SSF process.     

Utilization of Distillation Residue of 2nd Generation Bioethanol for Fine Chemicals Production

Distillation residue was waste containing huge amount of water. However, it could not through away to environment due to water pollution. Therefore, some treatments were required. Distillation residue of 2^nd generation bioethanol based palm oil empty fruit bunch was hydrothermal liquefied to increase its added value. Process hydrothermal liquefaction was carried out under variation of temperature and reaction time, in an autoclave under inert atmosphere. The product consisted of tar dissolved in water, char and gas. The solid conversion, the tar yields and chemical compounds yields increased by the increasing the reaction temperature. The reaction time did not give significant effect to the conversion and the tar yields (wt %). However, reaction time gave a significant effect to typical chemical compounds in the tar. The typical chemical compounds identified in the tar were acetic acid, phenol, phenol,-2-methoxy and 2-pyrrolidinone. Acetic acid as a fine chemical derived from the distillation residue was recovered as 84% mol after reaction at 325°C for 60min.     

Evaluation and Optimization of Organic Acid Pretreatment of Cotton Gin Waste for Enzymatic Hydrolysis and Bioethanol Production

This paper investigates the efficiency of the organic acids on the pretreatment of an industrially generated cotton gin waste for the removal of lignin, thereby releasing cellulose and hemicellulose as fermentable sugar components. Cotton gin waste was pretreated with various organic acids namely lactic acid, oxalic acid, citric acid, and maleic acid. Among these, maleic acid was found to be the most efficient producing maximum xylose sugar (126.05?±?0.74 g/g) at the optimum pretreatment condition of 150 °C, 500 mM, and 45 min. The pretreatment efficiency was comparable to the conventional dilute sulfuric acid pretreatment. A lignin removal of 88% was achieved by treating maleic acid pretreated biomass in a mixture of sodium sulfite and sodium chlorite. The pretreated biomass was further evaluated for the release of sugar by enzymatic hydrolysis and subsequently bioethanol production from hydrolysates. The maximum 686.13 g/g saccharification yield was achieved with maleic acid pretreated biomass which was slightly higher than the sulfuric acid (675.26 g/g) pretreated waste. The fermentation of mixed hydrolysates(41.75 g/l) produced 18.74 g/l bioethanol concentration with 2.25 g/l/h ethanol productivity and 0.48 g/g ethanol yield using sequential use of Saccharomyces cerevisiae and Pichia stipitis yeast strains. The production of bioethanol was higher than the ethanol produced using co-culture in comparison to sequential culture. Thus, it has been demonstrated that the maleic acid pretreatment and fermentation using sequential use of yeast strains are efficient for bioethanol production from cotton gin waste.     

Bioethanol Production from Glucose by Thermophilic Microbes from Ciater Hot Springs

Bioethanol has been considered as one of the alternative energy resources for fossil fuel substitute. Second generation of bioethanol production usually uses lignocellulosic material as its raw material which conducted at high temperature range (70-80^oC). In this case the thermophilic microbe is needed for fermentation process in order to minimize the use of energy. This paper will discuss the results of the study on bioethanol production from glucose by using thermophilic microbes isolated from local source namely from Ciater hot springs in Subang District, Indonesia. In this study six thermophilic isolates (C1, C2, C3, C4, C5 and C6) were tested their capability in producing ethanol in the fermentation medium containing 5% glucose substrate for 5 days incubation. To determine the activity of isolates in ferment substrate is done by measuring the concentration of glucose and ethanol produced using a spectrophotometer. Isolates tested (C1,C2,C3,C4 and C5) could reduce glucose concentration from 1.1up to 1.7% in the fermentation medium. The ethanol produced was tested qualitatively by reacting the samples with K₂Cr₂O₇inacidic conditions by observing its color change from yellow-orange to green-blue. The presence of ethanol indicatedby the decrease of OD's sample. This study showed that all isolates have the ability to produce ethanol. However, there are 2 isolates potentially produce ethanol that isolates C3 and C5 are characterized by low absorbance after adding potassium dichromate (K₂Cr₂O₇).     

Fumaric Acid Production from Alkali-Pretreated Corncob by Fed-Batch Simultaneous Saccharification and Fermentation Combined with Separated Hydrolysis and Fermentation at High Solids Loading

Production of fumaric acid from alkali-pretreated corncob (APC) at high solids loading was investigated using a combination of separated hydrolysis and fermentation (SHF) and fed-batch simultaneous saccharification and fermentation (SSF) by Rhizopus oryzae. Four different fermentation modes were tested to maximize fumaric acid concentration at high solids loading. The highest concentration of 41.32 g/L fumaric acid was obtained from 20 % (w/v) APC at 38 °C in the combined SHF and fed-batch SSF process, compared with 19.13 g/L fumaric acid in batch SSF alone. The results indicated that a combination of SHF and fed-batch SSF significantly improved production of fumaric acid from lignocellulose by R. oryzae than that achieved with batch SSF at high solids loading.     

Performance of Commercial and Laboratory Membranes for Recovering Bioethanol from Fermentation Broth by Thermopervaporation

A poly[1-(trimethylsilyl)-1-propyne] membrane was studied in a thermopervaporation process for ethanol recovery from fermentation media. Four commercial composite membranes based on polysiloxanes (Pervap 4060, Pervatech PDMS, PolyAn, and MDK-3) were studied for comparison. The dependences of the permeate flux, permeate concentration, separation factor, and pervaporation separation index on the temperature of the feed mixture (5 wt % ethanol in water) were obtained. The maximal values of the ethanol concentration in the permeate (35 wt %) and separation factor (10.2) were obtained for the poly[1-(trimethylsilyl)-1-propyne] membrane, whereas the PolyAn membrane provided the highest permeate flux (5.4 kg m^–2 h^–1). The ethanol/ water separation factor for the systems studied has a maximum at 60°С; this temperature of the feed mixture is optimum for recovering ethanol from aqueous media by thermopervaporation. The existing membranes based on polysiloxanes show low ethanol–water selectivity (less than 1). Poly[1-(trimethylsilyl)-1-propyne] membranes are the most promising for recovering bioethanol from fermentation mixtures by thermopervaporation, because they showed the highest selectivity to ethanol.     

Effect of Double-Step Steam Explosion Pretreatment in Bioethanol Production from Softwood

The study investigated the production of bioethanol from softwood, in particular pine wood chip. The steam explosion pretreatment was largely investigated, evaluating also the potential use of a double-step process to increase ethanol production through the use of both solid and liquid fraction after the pretreatment. The pretreatment tests were carried out at different conditions, determining the composition of solid and liquid fraction and steam explosion efficiency. The enzymatic hydrolysis was carried out with Ctec2 enzyme while the fermentation was carried out using Saccharomyces Cerevisiae yeast “red ethanol”. It was found that the best experimental result was obtained for a single-step pretreated sample (10.6 g of ethanol/100 g of initial biomass dry basis) for a 4.53 severity. The best double-step overall performance was equal to 8.89 g ethanol/100 g of initial biomass dry basis for a 4.27 severity. The enzymatic hydrolysis strongly depended on the severity of the pretreatment while the fermentation efficiency was mainly influenced by the concentration of the inhibitors. The ethanol enhancing potential of a double-step steam explosion could slightly increase the ethanol production compared to single-step potential.     

Optimization of Bioethanol Production from Enzymatic Treatment of Argan Pulp Feedstock

Argan pulp is an abundant byproduct from the argan oil process. It was investigated to study the feasibility of second-generation bioethanol production using, for the first time, enzymatic hydrolysis pretreatment. Argan pulp was subjected to an industrial grinding process before enzymatic hydrolysis using Viscozyme L and Celluclast 1.5 L, followed by fermentation of the resulting sugar solution by Saccharomyces cerevisiae. The argan pulp, as a biomass rich on carbohydrates, presented high saccharification yields (up to 91% and 88%) and an optimal ethanol bioconversion of 44.82% and 47.16% using 30 FBGU/g and 30 U/g of Viscozyme L and Celluclast 1.5 L, respectively, at 10%_w/v of argan biomass.     

Production of High-Octane Gasolines from Bioethanol on Zn-Modified HZSM-5 Zeolite

Moscow University Chemistry Bulletin - The influence of the concentration of zinc introduced into HZSM-5 on its acidic and catalytic properties in the conversion of ethanol into high-octane...     

Bioethanol Production from Uncooked Raw Starch by Immobilized Surface-engineered Yeast Cells

Surface-engineered yeast Saccharomyces cerevisiae codisplaying Rhizopus oryzae glucoamylase and Streptococcus bovis α-amylase on the cell surface was used for direct production of ethanol from uncooked raw starch. By using 50 g/L cells during batch fermentation, ethanol concentration could reach 53 g/L in 7 days. During repeated batch fermentation, the production of ethanol could be maintained for seven consecutive cycles. For cells immobilized in loofa sponge, the concentration of ethanol could reach 42 g/L in 3 days in a circulating packed-bed bioreactor. However, the production of ethanol stopped thereafter because of limited contact between cells and starch. The bioreactor could be operated for repeated batch production of ethanol, but ethanol concentration dropped to 55% of its initial value after five cycles because of a decrease in cell mass and cell viability in the bioreactor. Adding cells to the bioreactor could partially restore ethanol production to 75% of its initial value.     

Onsite Enzyme Production During Bioethanol Production from Biomass: Screening for Suitable Fungal Strains

Cellulosic ethanol production from biomass raw materials involves process steps such as pre-treatment, enzymatic hydrolysis, fermentation, and distillation. Use of streams within cellulosic ethanol production was explored for onsite enzyme production as part of a biorefinery concept. Sixty-four fungal isolates were in plate assays screened for lignocellulolytic activities to discover the most suitable fungal strain with efficient hydrolytic enzymes for lignocellulose conversion. Twenty-five were selected for further enzyme activity studies using a stream derived from the bioethanol process. The filter cake left after hydrolysis and fermentation was chosen as substrate for enzyme production. Five of the 25 isolates were further selected for synergy studies with commercial enzymes, Celluclast 1.5L and Novozym 188. Finally, IBT25747 (Aspergillus niger) and strain AP (CBS 127449, Aspergillus saccharolyticus) were found as promising candidates for onsite enzyme production where the filter cake was inoculated with the respective fungus and in combination with Celluclast 1.5L used for hydrolysis of pre-treated biomass.     

Improvement of Highly Thermostable Xylanases Production by Talaromyces thermophilus for the Agro-industrials Residue Hydrolysis

A newly isolated thermophilic fungal strain from Tunisian soil samples was identified as Talaromyces thermophilus and was selected for its ability to produce extracellular hemicellulases when grown on various lignocellulosic substrates. Following the optimization of carbon source, nitrogen source, and initial pH of the growth medium in submerged liquid cultures, yields as high as 10.00?±?0.15 and 0.21?±?0.02 U/ml were obtained for xylanase and β-xylosidase, respectively. In fact, wheat bran was found to be a good inducer of hemicellulase enzymes, mainly β-xylosidase. The optimal temperature and pH of the xylanase activity were 75°C and 8.0, respectively. This enzyme exhibited a remarkable stability and retained 100% of its original activity at 50°C for 7 days at pH?7.0–8.0. The half-lives of the enzyme were 4 h at 80°C, 2 h at 90°C, and 1 h at 100°C. T. thermophilus could therefore be considered as a satisfactory and promising producer of thermostable xylanases. Crude enzyme of T. thermophilus rich in xylanase and β-xylosidase was established for the hydrolysis of lignocellulosic materials as wheat bran.     

Bioethanol Production from Ipomoea Carnea Biomass Using a Potential Hybrid Yeast Strain

The paper deals with the exploitation of Ipomoea carnea as a feedstock for the production of bioethanol. Dilute acid pretreatment under optimum conditions (3 %H₂SO₄, 120 °C for 45 min) produced 17.68 g L^?1 sugars along with 1.02 g L^?1 phenolics and 1.13 g L^?1 furans. A combination of overliming and activated charcoal adsorption facilitated the removal of 91.9 % furans and 94.7 % phenolics from acid hydrolysate. The pretreated biomass was further treated with a mixture of sodium sulphite and sodium chlorite and, a maximum lignin removal of 81.6 % was achieved. The enzymatic saccharification of delignified biomass resulted in 79.4 % saccharification with a corresponding sugar yield of 753.21 mg g^?1. Equal volume of enzymatic hydrolysate and acid hydrolysate were mixed and used for fermentation with a hybrid yeast strain RPRT90. Fermentation of mixed detoxified hydrolysate at 30 °C for 28 h produced ethanol with a yield of 0.461 g g^?1. A comparable ethanol yield (0.414 g g^?1) was achieved using a mixture of enzymatic hydrolysate and undetoxified acid hydrolysate. Thus, I. carnea biomass has been demonstrated to be a potential feedstock for bioethanol production, and the use of hybrid yeast may pave the way to produce bioethanol from this biomass.     

Potential of Agricultural Residues and Hay for Bioethanol Production

Production of bioethanol from agricultural residues and hays (wheat, barley, and triticale straws, and barley, triticale, pearl millet, and sweet sorghum hays) through a series of chemical pretreatment, enzymatic hydrolysis, and fermentation processes was investigated in this study. Composition analysis suggested that the agricultural straws and hays studied contained approximately 28.62-38.58% glucan, 11.19-20.78% xylan, and 22.01-27.57% lignin, making them good candidates for bioethanol production. Chemical pretreatment with sulfuric acid or sodium hydroxide at concentrations of 0.5, 1.0, and 2.0% indicated that concentration and treatment agent play a significant role during pretreatment. After 2.0% sulfuric acid pretreatment at 121 degrees C/15 psi for 60 min, 78.10-81.27% of the xylan in untreated feedstocks was solubilized, while 75.09-84.52% of the lignin was reduced after 2.0% sodium hydroxide pretreatment under similar conditions. Enzymatic hydrolysis of chemically pretreated (2.0% NaOH or H2SO4) solids with Celluclast 1.5 L-Novozym 188 (cellobiase) enzyme combination resulted in equal or higher glucan and xylan conversion than with Spezyme(R) CP- xylanase combination. The glucan and xylan conversions during hydrolysis with Celluclast 1.5 L-cellobiase at 40 FPU/g glucan were 78.09 to 100.36% and 74.03 to 84.89%, respectively. Increasing the enzyme loading from 40 to 60 FPU/g glucan did not significantly increase sugar yield. The ethanol yield after fermentation of the hydrolyzate from different feedstocks with Saccharomyces cerevisiae ranged from 0.27 to 0.34 g/g glucose or 52.00-65.82% of the theoretical maximum ethanol yield.     

Production of Ethanol and Feed by High Dry Matter Hydrolysis and Fermentation of Palm Kernel Press Cake

Palm kernel press cake (PKC) is a residue from palm oil extraction presently only used as a low protein feed supplement. PKC contains 50% fermentable hexose sugars present in the form of glucan and mainly galactomannan. This makes PKC an interesting feedstock for processing into bioethanol or in other biorefinery processes. Using a combination of mannanase, β-mannosidase, and cellulases, it was possible without any pretreatment to hydrolyze PKC at solid concentrations of 35% dry matter with mannose yields up to 88% of theoretical. Fermentation was tested using Saccharomyces cerevisiae in both a separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) setup. The hydrolysates could readily be fermented without addition of nutrients and with average fermentation yields of 0.43?±?0.02 g/g based on consumed mannose and glucose. Employing SSF, final ethanol concentrations of 70 g/kg was achieved in 216 h, corresponding to an ethanol yield of 70% of theoretical or 200 g ethanol/kg PKC. Testing various enzyme mixtures revealed that including cellulases in combination with mannanases significantly improved ethanol yields. Processing PKC to ethanol resulted in a solid residue enriched in protein from 17% to 28%, a 70% increase, thereby potentially making a high-protein containing feed supplement.     

Enhanced Bioethanol Production from Potato Peel Waste Via Consolidated Bioprocessing with Statistically Optimized Medium

In this study, an extensive screening was undertaken to isolate some amylolytic microorganisms capable of producing bioethanol from starchy biomass through Consolidated Bioprocessing (CBP). A total of 28 amylolytic microorganisms were isolated, from which 5 isolates were selected based on high α-amylase and glucoamylase activities and identified as Candida wangnamkhiaoensis, Hyphopichia pseudoburtonii (2 isolates), Wickerhamia sp., and Streptomyces drozdowiczii based on 26S rDNA and 16S rDNA sequencing. Wickerhamia sp. showed the highest ethanol production (30.4 g/L) with fermentation yield of 0.3 g ethanol/g starch. Then, a low cost starchy waste, potato peel waste (PPW) was used as a carbon source to produce ethanol by Wickerhamia sp. Finally, in order to obtain maximum ethanol production from PPW, a fermentation medium was statistically designed. The effect of various medium ingredients was evaluated initially by Plackett-Burman design (PBD), where malt extracts, tryptone, and KH₂PO₄ showed significantly positive effect (p value < 0.05). Using Response Surface Modeling (RSM), 40 g/L (dry basis) PPW and 25 g/L malt extract were found optimum and yielded 21.7 g/L ethanol. This study strongly suggests Wickerhamia sp. as a promising candidate for bioethanol production from starchy biomass, in particular, PPW through CBP.     

Improved Bioethanol Production Using Fusants of Saccharomyces cerevisiae and Xylose-Fermenting Yeasts

The present research deals with the development of a hybrid yeast strain with the aim of converting pentose and hexose sugar components of lignocellulosic substrate to bioethanol by fermentation. Different fusant strains were obtained by fusing protoplasts of Saccharomyces cerevisiae and xylose-fermenting yeasts such as Pachysolen tannophilus, Candida shehatae and Pichia stipitis. The fusants were sorted by fluorescent-activated cell sorter and further confirmed by molecular characterization. The fusants were evaluated by fermentation of glucose?Cxylose mixture and the highest ethanol producing fusant was used for further study to ferment hydrolysates produced by acid pretreatment and enzymatic hydrolysis of cotton gin waste. Among the various fusant and parental strains used under present study, RPR39 was found to be stable and most efficient strain giving maximum ethanol concentration (76.8?±?0.31?g L^?1), ethanol productivity (1.06?g L^?1 h^?1) and ethanol yield (0.458?g g^?1) by fermentation of glucose?Cxylose mixture under test conditions. The fusant has also shown encouraging result in fermenting hydrolysates of cotton gin waste with ethanol concentration of 7.08?±?0.142?g L^?1, ethanol yield of 0.44?g g^?1, productivity of 0.45?g L^?1?h^?1 and biomass yield of 0.40?g g^?1.     

Production of Thermostable Lipase by Thermomyces lanuginosus on Solid-State Fermentation: Selective Hydrolysis of Sardine Oil

A naturally immobilized biocatalyst with lipase activity was produced by Thermomyces lanuginosus on solid-state fermentation with perlite as inert support. Maxima lipase activities (22 and 120 U/g of dry matter, using p-nitrophenyl octanoate and trioctanoine, respectively, as substrates) were obtained after 72 h of solid culture, remaining nearly constant up to 120 h. Maxima lipase activity was found at 60 to 85 °C and pH 10. The biocatalyst was stable at 60 °C for at least 4 h of incubation and a pH from 7 to 10. Energy values of activation and deactivation of lipase were of 26 and 6.7 kJ/mol, respectively. The biocatalyst shows high selectivity for the release of the omega-3 polyunsaturated fatty acids, eicosapentaenoic (EPA) and docosahexaenoic acids (DHA), during the hydrolysis of sardine oil. The EPA/DHA ratio (16:6) released by this biocatalyst was superior to that obtained with the commercial preparations of T. lanuginosus.