Simultaneous Saccharification And Co-fermentation Research Articles

Co-fermentation exploiting glucose and xylose utilizing thermotolerant S. cerevisiae of highly lignified biomass for biofuel production: Statistical optimization and kinetic models

The present study assesses the potential of co-fermentation for the enhanced production of biofuels from a highly lignified biomass, Viz., Pomegranate Peel (PP) and Mosambi Peel (PP). The simultaneous saccharification and co-fermentation (SScF) on brewer's yeast Saccharomyces cerevisiae and modified strain S. cerevisiae XUSE were used for the ethanol production using RSM. The Box-Behnken design (BBD) model was used to execute 15 runs with independent factors of initial pH (5.5, 6.5, 7.5), yeast concentration (4%, 5% and 6%v/v), and co-culture yeast concentration (4%, 5% and 6%v/v). The highest bioethanol production was achieved by PP (35.460 ± 0.32 g/L) and MP (25.630 ± 0.40 g/L) on optimal variables of pH 6.5, with yeast concentration (5% v/v) and co-culture yeast concentration (5% v/v) for 120 hrs duration. Furthermore, the kinetic of logistic and modified Gompertz model analyzed the lag phase of PP and MP was 7.9 and 7.15 h, for which maximum bioethanol production (EtOH max-Pm) reported for PP (38.62 g/L) and MP (29.21 g/L), respectively. The study infers that SScF has great potential for producing high-titer ethanol commercially and supports waste-to-energy strategies.

Third-generation D-lactic acid production using red macroalgae Gelidium amansii by co-fermentation of galactose, glucose and xylose

Macroalgae biomass has been considered as a promising renewable feedstock for lactic acid production owing to its lignin-free, high carbohydrate content and high productivity. Herein, the D-lactic acid production from red macroalgae Gelidium amansii by Pediococcus acidilactici was investigated. The fermentable sugars in G. amansii acid-prehydrolysate were mainly galactose and glucose with a small amounts of xylose. P. acidilactici could simultaneously ferment the mixed sugars of galactose, glucose and xylose into D-lactic acid at high yield (0.90 g/g), without carbon catabolite repression (CCR). The assimilating pathways of these sugars in P. acidilactici were proposed based on the whole genome sequences. Simultaneous saccharification and co-fermentation (SSCF) of the pretreated and biodetoxified G. amansii was also conducted, a record high of D-lactic acid (41.4 g/L) from macroalgae biomass with the yield of 0.34 g/g dry feedstock was achieved. This study provided an important biorefinery strain for D-lactic acid production from macroalgae biomass.

Hydrodynamic cavitation-assisted acid pretreatment and fed-batch simultaneous saccharification and co-fermentation for ethanol production from sugarcane bagasse using immobilized cells of Scheffersomyces parashehatae

A new alternative for hydrodynamic cavitation-assisted pretreatment of sugarcane bagasse was proposed, along with a simultaneous saccharification and co-fermentation (SSCF) process performed in interconnected columns. Influential variables in the pretreatment were evaluated using a statistical design, indicating that an ozone flow rate of 10 mg min−1 and a pH of 5.10 resulted in 86 % and 72 % glucan and xylan hydrolysis yields, respectively, in the subsequent enzymatic hydrolysis process. Under these optimized conditions, iron sulfate (15 mg L−1) was added to assess Fenton pretreatment, resulting in glucan and xylan hydrolysis yields of 92 % and 71 %, respectively, in a material pretreated for 10 min. In SSCF, ethanol volumetric productivities of 0.33 g L−1 h−1 and of 0.54 g L−1 h−1 were obtained in batch and fed-batch operation modes, achieving 26 g L−1 of ethanol in 48 h in the latter mode.

Bioconversion of Crop Residues Using Alternative Fermentation-Based Approaches.

Globally, the growing production of food commodities generates significant quantities of agroindustrial residues, most of which are untreated and disposed of as waste through either burning, dumping into the land, or unplanned landfilling, thereby causing environmental pollution, public health problems, and decreased soil organic matter and soil productivity. A literature review has been conducted on the current crop residue biomass valorization, analyzing raw material properties and the potential risks associated with its incorrect or absent management, as well as the major microbial fermentation strategies that are used for converting residual crops into valuable products. Approximately 2445.2 million tons of crop residues are produced worldwide. Microbial fermentation is an efficient way of managing residues that are rich in nutrients (e.g., nitrogen, phosphorus, and potassium) and converting them into single-cell proteins, antibiotics, enzymes, bioalcohols, polysaccharides, fine chemicals, and others, thereby supporting a circular bioeconomy. Although separate saccharification and fermentation (SHF) represent the predominant fermentation strategy, it requires considerable equipment costs and a long process time, which can lead to the formation of contaminations and inhibitors. Alternative conversion strategies, including simultaneous saccharification and fermentation (SSF), simultaneous saccharification and co-fermentation (SSCF), and consolidated bioprocessing (CBP), can reduce time and production costs, contaminations, and inhibitor formation, and enhance process yields. Nevertheless, combining hydrolysis and fermentation into a single phase results in non-optimal temperature and pH. This review discusses crop residue valorization through fermentation strategies, and provides a 360-degree view of the topic. After investigating the major types of crop residues and the potential environmental risks associated with their incorrect or absent management, it analyzes the key steps in the crop residue bioconversion process, and the most common microorganisms and microbial cultures. In addition, this review reports on various examples of crop residues being converted into industrial products and analyzes the main fermentation strategies (SHF, SSF, SSCF, and CBP), highlighting their strengths and weaknesses. As a matter of fact, fermentation strategies need to be compared for their benefits and disadvantages before being implemented on a large scale. In addition, the properties and availability of the raw materials, investment, and operating costs, the skilled workforce availability, sustainability, and the return on investment all need to be evaluated. Finally, the discussion focus on future outlooks and challenges.

Efficient production of lactic acid from cellulose and xylan in sugarcane bagasse by newly isolated Lactiplantibacillus plantarum and Levilactobacillus brevis through simultaneous saccharification and co-fermentation process

Sugarcane bagasse is one of the promising lignocellulosic feedstocks for bio-based chemicals production. However, to date, most research focuses mainly on the cellulose conversion process, while hemicellulose remains largely underutilized. The conversion of glucose and xylose derived from lignocellulosic biomass can be a promising strategy to improve utilization efficiencies of resources, energy, and water, and at the same time reduce wastes generated from the process. Here, attempts were made to convert cellulose and xylan in sugarcane bagasse (SB) into lactic acid (LA) through a pre-hydrolysis and simultaneous saccharification and co-fermentation (SScF) process using newly isolated Lactiplantibacillus plantarum TSKKU P-8 and Levilactobacillus brevis CHKKU N-6. The process yielded 91.9 g/L of LA, with a volumetric productivity of 0.85 g/(L·h). This was equivalent to 137.8 ± 3.4 g-LA, a yield on substrate (pretreated SB) of 0.86 g/g, and a productivity of 1.28 g/h, based on a final volume of 1.5 L. On the other hand, pre-hydrolysis and simultaneous saccharification and fermentation (SSF) process using La. plantarum TSKKU P-8 as a monoculture gave 86.7 ± 0.2 g/L of LA and a volumetric productivity of 0.8 g/(L·h), which were equivalent to 104.8 ± 0.3 g-LA, a yield on substrate of 0.65 g/g, and a productivity of 0.97 g/h, based on a final volume of 1.2 L. Mass balance calculated based on mass of raw SB entering the process showed that the SScF process improved the product yield by 32% as compared with SSF process, resulting in 14% improvement in medium-based economic yield.

Exploration of separate hydrolysis and fermentation and simultaneous saccharification and co-fermentation for acetone, butanol, and ethanol production from combined diluted acid with laccase pretreated Puerariae Slag in Clostridium beijerinckii ART44

In this study, an efficient pretreatment technology was developed for the bioconversion of puerariae slag (PS) into biobutanol. To accelerate the enzymatic saccharification of PS, the method of dilute acid combined with laccase pretreatment (DALP) was performed. With this effort, the highest concentration of reducing sugar was 48.96 ± 1.69 g/L after enzymatic hydrolysis of the whole slurry pretreatment under the optimal condition. Subsequently, the highest butanol productivity (0.15 g/L/h) was obtained by the simultaneous saccharification and co-fermentation (SSCF), which was 114.29% higher than that of the separate hydrolysis and fermentation (SHF). Furthermore, the microstructural changes of PS after different pretreatment were initially investigated by FT-IR, and we found that the DALP method resulted in more severe damage during the pretreatment process, which could improve the efficiency of enzymatic saccharification. This study suggests that the DALP is an attainable and efficient pretreatment method for production of butanol in the SSCF process.

Solid feeding and co-culture strategies for an efficient enzymatic hydrolysis and ethanol production from sugarcane bagasse

The feasibility of second-generation (2G) processes still highly depends on improvements in the hydrolysis and fermentation steps, ensuring the whole use of biomass sugars in an integrated approach. The main bottlenecks are the differences between the optimal conditions for both steps, limitations for high solid load (HSL) hydrolysis, and hexoses and pentose co-fermentation. To overcome these problems, the present work explored a feeding strategy to improve HSL enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse (PSB), at optimal and suboptimal temperatures, further integrated with a non-recombinant yeast co-culture (Saccharomyces cerevisiae and Kluyveromyces marxianus) for sugar co-fermentation. The entire PSB fraction was used without conditioning. Efficient enzymatic hydrolysis was achieved using a feeding strategy in a helical stirred bioreactor (64 and 75% cellulose conversion with 22.5% of solids, 72 h at 35 and 50 °C, respectively), obtaining hydrolysates with high glucose and xylose concentrations (100 g/L). Simultaneous saccharification and co-fermentation (SSCF) provided high glucose (98%) and xylose (52%) conversion in 24 deep-well plates, with ethanol yield of 0.23 getOH/gS, but faced problems of cell viability loss in the bioreactor. Sequential SCF (SqSCF) co-culture stood out as a promising strategy for the use of biomass sugars. The results of this study provide significant contribution to the intensification and feasibility of 2G production, in addition to highlighting the difficulties faced for process integration aiming at the full conversion of sugars coming from high solid load enzymatic hydrolysis.

Simultaneous and rate-coordinated conversion of lignocellulose derived glucose, xylose, arabinose, mannose, and galactose into D-lactic acid production facilitates D-lactide synthesis

D-lactide is the precursor of poly(D-lactide) (PDLA) or stereo-complex with poly(L-lactide) (PLLA). Lignocellulosic biomass provides the essential feedstock option to synthesize D-lactic acid and D-lactide. The residual sugars in D-lactic acid fermentation broth significantly blocks the D-lactide synthesis. This study showed a simultaneous and rate-coordinated conversion of lignocellulose derived glucose, xylose, arabinose, mannose, and galactose into D-lactic acid by adaptively evolved Pediococcus acidilactici ZY271 by simultaneous saccharification and co-fermentation (SSCF) of wheat straw. The produced D-lactic acid achieved minimum residual sugars (∼1.7 g/L), high chirality (∼99.1%) and high titer (∼128 g/L). A dry acid pretreatment eliminated the wastewater stream generation and the biodetoxification by fungus Amorphotheca resinae ZN1 removed the inhibitors from the pretreatment. The removal of the sugar residues and inhibitor impurities in D-lactic acid production from lignocellulose strongly facilitated the D-lactide synthesis. This study filled the gap in cellulosic D-lactide production from lignocellulose-derived D-lactic acid.

Enhanced cellulosic d-lactic acid production from sugarcane bagasse by pre-fermentation of water-soluble carbohydrates before acid pretreatment

After several rounds of milling process for sugars extraction from sugarcane, certain amounts of water-soluble carbohydrates (WSC) still remain in sugarcane bagasse. It is a bottleneck to utilize WSC in sugarcane bagasse biorefinery, since these sugars are easily degraded into inhibitors during pretreatment. Herein, a simple pre-fermentation step before pretreatment was conducted, and 98 % of WSC in bagasse was fermented into d-lactic acid. The obtained d-lactic acid was stably preserved in bagasse and 5-hydroxymethylfurfural (HMF) generation was sharply reduced from 46.0 mg/g to 6.2 mg/g of dry bagasse, after dilute acid pretreatment. Consequently, a higher d-lactic acid titer (57.0 g/L vs 33.2 g/L) was achieved from the whole slurry of the undetoxified and pretreated sugarcane bagasse by one-pot simultaneous saccharification and co-fermentation (SSCF), with the overall yield of 0.58 g/g dry bagasse. This study gave an efficient strategy for enhancing lactic acid production using the lignocellulosic waste from sugar industry.

Continuous simultaneous saccharification and co-fermentation (SSCF) for cellulosic L-lactic acid production

Continuous fermentation is preferred in industrial bioprocesses by its steady-state operation mode and the significant reduction of switch operation of vessels emptying, cleaning, and sterilizing. General biorefinery fermentation of lignocellulose is conducted in the mode of simultaneous saccharification and co-fermentation (SSCF) thus the continuous operation does not stand well because of the mismatch between the optimal temperatures of cellulase enzymes and microbial cells. This study challenged the continuous SSCF operation for production of high chiral purity L-lactic acid based on the dry biorefinery processing platform. An engineered thermophilic L-lactic acid bacterium Pediococcus acidilactici with complete non-glucose assimilation capacity and antibacterial activity with a nearly perfect match of temperature (42–50 °C) and pH (5.5) with that of cellulase enzyme used (50 °C, pH 4.8). This microbial cell factory allows the enzymatic hydrolysis and fermentation to be conducted simultaneously in one-pot bioreactor and provides the basis for establishing a valid continuous SSCF operation. The continuous SSCF of the biodetoxified wheat straw was established in cascade bioreactors and the performances of L-lactic acid titer, yield, and productivity reached 107.5 ± 1.1 g/L, 0.29 ± 0.01 g/g DM, and 2.69 ± 0.03 g/L/h, respectively. The chiral purity of the cellulosic L-lactic acid reached 99.5 %. The low residual sugar concentration and high-optical purity L-lactic acid product in broth facilitate the subsequent purification of L-lactic acid as the monomer for cyclic lactide or direct PLA synthesis. This multi-stage continuous SSCF technology overcomes the inherent barriers of the batch SSCF operation and provides a prototype for future industrial cellulosic lactic production.

Bioethanol Production from Rice Husk through SHCF and SSCF Processing Strategies

In many developing countries, there is great quest for achieving sustainable energy from the conversion of the huge biomass of organic wastes into useful biofuels such as bioethanol. Bioethanol is a renewable clean-liquid biofuel produced by fermentation of sugars or converted starch or cellulose from plant based feedstocks. It is conventionally produced from sugar and starch containing feedstocks. However, these feedstocks are unable to meet the global demand of bioethanol production due to their primary food value and legal pursuits against the legitimacy of their schemes. This study investigated and improved on the feasibility of producing bioethanol from rice husk agrowaste generated from rice production. It was first subjected to different physico-chemical pretreatments in order to optimize the hydrolysate sugar yield and identify the most effective process. It was further hydrolyzed by cellulase enzymes from Trichoderma ressei micro-organism isolated from the soil. Separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) strategies/methods were adopted using both hydrometer and Pycnometer measurements. The fermentation results revealed that the maximum bioethanol yield through SHCF and SSCF strategies were 4.64 and 6.45 (% w/v dry biomass) respectively. SSCF strategy was more effective as it gave better bioethanol yield and was less time consuming. This study also shows that rice husk agro-waste of no or little commercial value can be utilized in the production of good quality bioethanol with implications for improved waste management, income and efficient energy generation.

Comparative Studies on Bioethanol Production from Some Starch Based Agricultural Waste Peels

The potential of some starch-based agricultural waste peels (cassava peels, yam peels and potato peels) for bioethanol production was investigated. They were pretreated with physico-chemical agents before being hydrolyzed using cellulase enzymes from the Trichoderma ressei micro-organism. Using co-cultures of Saccharomyces cerevisiae and Pichia stipitis fermentative yeasts, the different hydrolysates were fermented to bioethanol. The bioethanol yields of separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) fermentative procedures were evaluated. The maximum bioethanol yields from the fermentation results for cassava peels, yam peels and potato peels were 4.87, 3.78 and 5.31 (% w/v wet biomass) respectively after 72 hours of fermentation. The SSCF method was shown to be more successful since it produced higher bioethanol yields in all of the substrates studied and was quicker. When compared to prior research using different microorganisms, the SSCF technique had a superior fermentation yield using mixed cultures of Trichoderma ressi, Saccharomyces cerevisiae and Pichia stipites.

Comparative Studies on Bioethanol Production from Some Sugar Based Agricultural Wastes

The suitability of some sugar-based agricultural wastes (pineapple peels, banana peels, and plantain peels) were examined for bioethanol production. They were subjected to different physico-chemical pretreatments in order to identify the most effective process and optimize the yield of bioethanol. They were further hydrolyzed by cellulase enzymes from Trichoderma ressei micro-organism isolated from the soil. The various hydrolysates obtained were subsequently fermented to bioethanol using co-cultures of Pichia stipitis and Saccharomyces cerevisiae fermentative yeasts. Separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) methods were adopted and their bioethanol yields compared. The fermentation results revealed that the maximum bioethanol yields for pineapple peels, banana peels, and plantain peels were 4.94, 3.85, and 4.57 (% w/v wet biomass) respectively at 72 hours fermentation period. SSCF strategy was observed to be more effective as it gave better bioethanol yields in all the considered substrates and was less time consuming. Mixed cultures of Trichoderma ressi, Pichia stipitis and Saccharomyces cerevisiae through SSCF process resulted to a better fermentation yield when compared with previous studies by other workers.

Bioethanol Production from Steam-Exploded Barley Straw by Co-Fermentation with Escherichia coli SL100

Second-generation bioethanol is considered a suitable option for replacing fossil fuels. Agricultural residues are being studied as feedstocks for sugar generation, which are in turn converted into ethanol. Among them, barley straw (BS) is a promising raw material, due to its high abundance, lignocellulosic composition and lack of other practical applications. Under these assumptions, the central aim of this study is to suggest an efficient bioethanol production scheme from BS at different levels of integration in co-fermentation with Escherichia coli SL100, including separate hydrolysis and co-fermentation (SHCF), simultaneous saccharification and co-fermentation (SSCF), and presaccharification and simultaneous saccharification and co-fermentation (PSSCF), using the water-insoluble solid (WIS) and slurry fractions obtained after steam explosion (SE) pretreatment. The best results in terms of ethanol yield were achieved following the SHCF process, using the WIS and the slurry as substrates, with yields of 89.1% and 78.8% of the theoretical maximum, respectively. Considering all of the above points, the following scheme is proposed for the conversion of BS into ethanol: SE pretreatment (160 °C, 30 min) of BS previously soaked overnight in 2.88% w/v phosphoric acid solution, filtration of the slurry, followed by enzymatic hydrolysis and co-fermentation of the two fractions obtained separately, with previous detoxification of the prehydrolysate with ammonium hydroxide (5 N). Under these conditions, 19.43 g of bioethanol was produced from 100 g of BS.

MODELLING, SIMULATION AND OPTIMIZATION OF BIOETHANOL PRODUCTION FROM LIGNOCELLULOSE MATERIALS USING OPEN-SOURCE SOFTWARE- SCILAB, R AND AP MONITOR

Bioethanol production from lignocellulose biomass has gained a lot of traction over the last two decades because it is a viable alternative energy source to fossil fuel and does not compete with the food supply like first-generation bioethanol does. In this study, previously reported research is used to generate mathematical models for enzymatic hydrolysis, and co-fermentation operations, which are then improved to include the decomposition of hemicellulose to xylose sugars. Two case studies were investigated and modelled in the Scilab and R software which are free and open-source software for numerical and statistical computing, respectively. The first case study examined the impact of alkaline loading and temperature (represented by A & B respectively) on delignification. Results show that A and A² are significant model terms and the optimum process parameters for delignification of 61% are 0.8% alkaline loading and 121℃. The second case investigated how the simultaneous saccharification and co-fermentation (SSCF) operation responds to the key control variables namely cellulose loading(A), hemicellulose loading(B), enzyme loading (C), yeast loading (D), temperature (E) and time (F). From the analysis of variance, the variables found to be significant model terms are: cellulose loading (A), enzyme loading (C), time (F), and then AF, A², C², F². Major parameters of the SSCF unit are then optimized using the APMonitor modeling package in Python to give 0.1263kg/kg minimum enzyme adsorbed per substrate loading, maximum cellulose conversion as 26.26% and a 47.9% maximum ethanol yield. Keywords: bioethanol; optimize; simultaneous saccharification and co-fermentation; dynamic modelling

Coprocessing Corn Germ Meal for Oil Recovery and Ethanol Production: A Process Model for Lipid-Producing Energy Crops

Efforts to engineer high-productivity crops to accumulate oils in their vegetative tissue present the possibility of expanding biodiesel production. However, processing the new crops for lipid recovery and ethanol production from cell wall saccharides is challenging and expensive. In a previous study using corn germ meal as a model substrate, we reported that liquid hot water (LHW) pretreatment enriched the lipid concentration by 2.2 to 4.2 fold. This study investigated combining oil recovery with ethanol production by extracting oil following LHW and simultaneous saccharification and co-fermentation (SSCF) of the biomass. Corn germ meal was again used to model the oil-bearing energy crops. Pretreated germ meal hydrolysate or solids (160 and 180 °C for 10 min) were fermented, and lipids were extracted from both the spent fermentation whole broth and fermentation solids, which were recovered by centrifugation and convective drying. Lipid contents in spent fermentation solids increased 3.7 to 5.7 fold compared to the beginning germ meal. The highest lipid yield achieved after fermentation was 36.0 mg lipid g−1 raw biomass; the maximum relative amount of triacylglycerol (TAG) was 50.9% of extracted oil. Although the fermentation step increased the lipid concentration of the recovered solids, it did not improve the lipid yields of pretreated biomass and detrimentally affected oil compositions by increasing the relative concentrations of free fatty acids.

Modified simultaneous saccharification and co-fermentation of DLC pretreated corn stover for high-titer cellulosic ethanol production without water washing or detoxifying pretreated biomass

Corn stover (CS) pretreated by DLC (Densifying Lignocellulosic biomass with acidic Chemicals) pretreatment exhibited higher digestibility and much better fermentability compared to traditional pretreatments. Nevertheless, the xylose fermentation, which was a key for lignocellulosic ethanol production, during SHCF (Separate Hydrolysis and Co-Fermentation) was unsatisfactory at high solid loadings. In this study, modified SSCF (Simultaneous Saccharification and Co-Fermentation) was adopted to promote xylose utilization and ethanol yield. SSCF conditions (temperature, inoculation size, nitrogen source addition) were investigated. A novel strategy “Fed-batch of DLC Biomass and Enzyme (FBE)” was developed for SSCF at 28%–35% solid loadings, which showed higher sugar conversion, higher xylose consumption and superior ethanol yield compared to SHCF and traditional SSCF. The highest ethanol titer of 74.6 g/L produced based on DLC pretreatment was achieved during FBE SSCF without water washing or detoxification of DLC-CS.

Comparative Studies On Bioethanol Production From Some Starch Based Agricultural Waste Peels

The potential of some starch-based agricultural waste peels (cassava peels, yam peels and potato peels) for bioethanol production was investigated. They were pretreated with physico-chemical agents before being hydrolyzed using cellulase enzymes from the Trichoderma ressei micro-organism. Using co-cultures of Saccharomyces cerevisiae and Pichia stipitis fermentative yeasts, the different hydrolysates were fermented to bioethanol. The bioethanol yields of separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) fermentative procedures were evaluated. The maximum bioethanol yields from the fermentation results for cassava peels, yam peels and potato peels were 4.87, 3.78 and 5.31 (% w/v wet biomass) respectively after 72 hours of fermentation. The SSCF method was shown to be more successful since it produced higher bioethanol yields in all of the substrates studied and was quicker. When compared to prior research using different microorganisms, the SSCF technique had a superior fermentation yield using mixed cultures of Trichoderma ressi, Saccharomyces cerevisiae and Pichia stipites.

Bioethanol Production From Rice Husk Through Shcf And Sscf Processing Strategies

In many developing countries, there is great quest for achieving sustainable energy from the conversion of the huge biomass of organic wastes into useful biofuels such as bioethanol. Bioethanol is a renewable clean-liquid biofuel produced by fermentation of sugars or converted starch or cellulose from plant based feedstocks. It is conventionally produced from sugar and starch containing feedstocks. However, these feedstocks are unable to meet the global demand of bioethanol production due to their primary food value and legal pursuits against the legitimacy of their schemes. This study investigated and improved on the feasibility of producing bioethanol from rice husk agro-waste generated from rice production. It was first subjected to different physico-chemical pretreatments in order to optimize the hydrolysate sugar yield and identify the most effective process. It was further hydrolyzed by cellulase enzymes from Trichoderma ressei micro-organism isolated from the soil. Separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) strategies/methods were adopted using both hydrometer and Pycnometer measurements. The fermentation results revealed that the maximum bioethanol yield through SHCF and SSCF strategies were 4.64 and 6.45 (% w/v dry biomass) respectively. SSCF strategy was more effective as it gave better bioethanol yield and was less time consuming. This study also shows that rice husk agro-waste of no or little commercial value can be utilized in the production of good quality bioethanol with implications for improved waste management, income and efficient energy generation.

Comparative Studies On Bioethanol Production From Some Sugar Based Agricultural Wastes

The suitability of some sugar-based agricultural wastes (pineapple peels, banana peels, and plantain peels) were examined for bioethanol production. They were subjected to different physico-chemical pretreatments in order to identify the most effective process and optimize the yield of bioethanol. They were further hydrolyzed by cellulase enzymes from Trichoderma ressei micro-organism isolated from the soil. The various hydrolysates obtained were subsequently fermented to bioethanol using co-cultures of Pichia stipitis and Saccharomyces cerevisiae fermentative yeasts. Separate hydrolysis and co-fermentation (SHCF) and simultaneous saccharification and co-fermentation (SSCF) methods were adopted and their bioethanol yields compared. The fermentation results revealed that the maximum bioethanol yields for pineapple peels, banana peels, and plantain peels were 4.94, 3.85, and 4.57 (% w/v wet biomass) respectively at 72 hours fermentation period. SSCF strategy was observed to be more effective as it gave better bioethanol yields in all the considered substrates and was less time consuming. Mixed cultures of Trichoderma ressi, Pichia stipitis and Saccharomyces cerevisiae through SSCF process resulted to a better fermentation yield when compared with previous studies by other workers.