Microwave-Assisted Alkali Delignification Coupled with Non-Ionic Surfactant Effect on the Fermentable Sugar Yield from Agricultural Residues of Cassava

Cassava stem, leaves and peel are agricultural residues generated as waste biomass during the cultivation and processing of cassava. The potential of these biomasses as feedstock for ethanol production depends on the effective deconstruction via pretreatment and saccharification. The effect of alkaline hydrogen peroxide (AHP) treatment on microwave (MW)-irradiated or steam-exposed aqueous slurry was compared with MW-irradiation (300 W) of alkali slurry in delignifying the biomass and degrading the polysaccharides. Cellulose was degraded to a higher extent than hemicellulose in the AHP treatments. The steam-exposed and AHP pretreated residues on saccharification with Cellic (Cellulase complex) alone or Cellic along with Tween 20 resulted in high conversion of carbohydrate to reducing sugars (RS) in leaves (64-70%) and peel (74- 78%), with slightly lower conversion in stem. MW-irradiation of alkali slurry (5 min.) followed by Tween 20 supplemented saccharification was a better strategy degrading cellulose and hemicellulose to very high extent. Tween 20 supplementation was beneficial in enhancing the RS release from the biomasses even when Cellic dosage was halved. Ultrastructural studies indicated the disappearance of starch granules from stem and peel samples after MW-irradiation and saccharification, while fragmented cellulose fibers were visible in leaf samples. The study showed that MW-assisted alkali pretreatment followed by saccharification with Cellic in presence of Tween 20 was very effective in releasing maximum sugars from these biomasses

Enhanced direct fermentation of cassava to butanol by Clostridium species strain BOH3 in cofactor-mediated medium

10.1186/s13068-015-0351-7Biotechnology for Biofuels8116

The Potential of Cellulosic Ethanol Production from Grasses in Thailand

The grasses in Thailand were analyzed for the potentiality as the alternative energy crops for cellulosic ethanol production by biological process. The average percentage composition of cellulose, hemicellulose, and lignin in the samples of 18 types of grasses from various provinces was determined as 31.85–38.51, 31.13–42.61, and 3.10–5.64, respectively. The samples were initially pretreated with alkaline peroxide followed by enzymatic hydrolysis to investigate the enzymatic saccharification. The total reducing sugars in most grasses ranging from 500–600 mg/g grasses (70–80% yield) were obtained. Subsequently, 11 types of grasses were selected as feedstocks for the ethanol production by simultaneous saccharification and cofermentation (SSCF). The enzymes, cellulase and xylanase, were utilized for hydrolysis and the yeasts, Saccharomyces cerevisiae and Pichia stipitis, were applied for cofermentation at 35°C for 7 days. From the results, the highest yield of ethanol, 1.14 g/L or 0.14 g/g substrate equivalent to 32.72% of the theoretical values was obtained from Sri Lanka ecotype vetiver grass. When the yields of dry matter were included in the calculations, Sri Lanka ecotype vetiver grass gave the yield of ethanol at 1,091.84 L/ha/year, whereas the leaves of dwarf napier grass showed the maximum yield of 2,720.55 L/ha/year (0.98 g/L or 0.12 g/g substrate equivalent to 30.60% of the theoretical values)

Enzymatic hydrolysis of cassava stalk pretreated with the alkaline method

This study was developed with the aim of evaluating the pH, enzymatic complex load and temperature effects on the saccharification of pretreated cassava stalks (CS) using the response surface methodology (RSM). The factor levels evaluated were temperature 35 - 40°C, pH 4.0 - 5.0 and dose of enzymatic complex Accellerase 1500™ 2.9 - 14.5 FPU/g of substrate. The reducing sugar (RS) response was used. The pH was controlled through the use of hydrochloric acid and sodium hydroxide solutions and the system was shaken orbitally at 120 rpm with a solids loading of 10% w/v. The fitted model showed that the optimal operating conditions were: pH 4.0, 38°C and enzyme dose of 14.5 FPU/g substrate, reaching a sugar concentration of 18.4 g L-1

A Review on 1st and 2nd Generation Bioethanol Production-Recent Progress

Today's society is based on the use of fossil resources for transportation fuels. The result of unlimited consumption of fossil fuels is a severe depletion of the natural reserves and damage to the environment. Depleting fossil reserves and increasing demand for energy together with environmental concerns have motivated researchers towards the development of alternative fuels which are eco-friendly, renewable and economical. Bioethanol is one such dominant global renewable transport biofuel which can readily substitute fossil fuels. Conventionally, bioethanol has been produced from sucrose and starch rich feedstocks (edible agricultural crops and products) known as 1st generation bioethanol; however this substrate conflicts with food and feed production. As an alternative to 1st generation bioethanol, currently there is much focus on advancing a cellulosic bioethanol concept that utilizes lignocellulosic residues from agricultural crops and residues (such as bagasse, straw, stover, stems, leaves and deoiled seed residues). Efficient conversion of lignocellulosic biomass into bioethanol remains an area of active research in terms of pretreatment of the biomass to fractionate its constituents (cellulose, hemicellulose and lignin), breakdown of cellulose and hemicellulose into hexose and pentose sugars and co-fermentation of the sugars to ethanol. The present review discusses research progress in bioethanol production from sucrose, starch and cellulosic feedstocks. Development of efficient technology to convert lignocellulosic biomass into fermentable sugars and optimization of enzymatic hydrolysis using on-site/ in-house enzyme preparation are the key areas of development in lignocellulosic bioethanol production. Moreover, finding efficient fermenting microorganisms which can utilize pentose and hexose sugars in their metabolism to produce ethanol together with minimum foam and glycerol formation is also an important parameter in fermentation. Research has been focus

Enzyme hydrolysis of cassava peels for ethanol production

The enzyme hydrolysis of cassava peels for ethanol production provides an interesting research opportunity to convert starch rich lignocellulose waste into renewable fuel production. The research involved the pretreatment of cassava peels with steam explosion and hot water pretreatment processes as well as combining both amylolytic and cellulolytic enzymes to produce simple sugars. This research compared different enzyme treatment strategies; a separate hydrolysis that involved the treatment of the peels with either cellulolytic enzymes or amylolytic enzymes, a consecutive hydrolysis process which is a follow up of the separate hydrolysis in which sugars were washed from the initial enzyme treatment (amylase or cellulase treatment) and the cassava peels resuspended for further enzyme treatment was also investigated. Another treatment strategy employed in this study was the simultaneous hydrolysis by amylases and cellulases of the cassava peels. The hydrolysis rate and yield were compared for each process. Minor changes that incorporated steam explosion pretreatment and hot water pretreatment were also studied. A separate hydrolysis of milled cassava peels treated by amylolytic and cellulolytic enzymes yielded a maximum reducing sugar of 0.41g (as glucose) per gram of peels and 0.31g per gram of peels respectively. Also steam exploded cassava peels treated by amylolytic and cellulolytic enzymes yielded maximum reducing sugars of 0.24g per gram of peels and 0.37g per gram of peels respectively. Results also showed that a consecutive treatment that incorporates an initial hydrolysis by cellulolytic enzymes followed by a subsequent treatment by amylolytic treatment yielded reducing sugars of 0.64g per gram of milled cassava peels. A reverse treatment where the cellulolytic enzymes were used to first treat the peels before a second treatment by amylolytic enzymes yielded 0.61g reducing sugar per gram of milled cassava peels. A simultaneous hydrolysis by both cellulolytic and amylolytic enzymes produced a maximum reducing sugar of 0.58g per gram of milled cassava peels. A modification that incorporates hot water pretreatment, simultaneous and consecutive treatment was carried out. The milled cassava peels treated with hot water at 1000C and amylase enzymes for 2 hours were further subjected to a simultaneous saccharification by cellulases and glucoamylase enzymes yielded a reducing sugar of 0.62g per gram of peels. Fermentation experiments were also carried out with Kluyveromyces marxianus at 400C and results showed a maximum ethanol yield of 0.12g ethanol per g of cassava peels for a separate hydrolysis and fermentation process and 0.18g ethanol per g of cassava peels for the simultaneous saccharification and fermentation process. It was concluded that cassava peels presents a very good source of sugars for bioethanol production.The enzyme hydrolysis of cassava peels for ethanol production provides an interesting research opportunity to convert starch rich lignocellulose waste into renewable fuel production. The research involved the pretreatment of cassava peels with steam explosion and hot water pretreatment processes as well as combining both amylolytic and cellulolytic enzymes to produce simple sugars. This research compared different enzyme treatment strategies; a separate hydrolysis that involved the treatment of the peels with either cellulolytic enzymes or amylolytic enzymes, a consecutive hydrolysis process which is a follow up of the separate hydrolysis in which sugars were washed from the initial enzyme treatment (amylase or cellulase treatment) and the cassava peels resuspended for further enzyme treatment was also investigated. Another treatment strategy employed in this study was the simultaneous hydrolysis by amylases and cellulases of the cassava peels. The hydrolysis rate and yield were compared for each process. Minor changes that incorporated steam explosion pretreatment and hot water pretreatment were also studied. A separate hydrolysis of milled cassava peels treated by amylolytic and cellulolytic enzymes yielded a maximum reducing sugar of 0.41g (as glucose) per gram of peels and 0.31g per gram of peels respectively. Also steam exploded cassava peels treated by amylolytic and cellulolytic enzymes yielded maximum reducing sugars of 0.24g per gram of peels and 0.37g per gram of peels respectively. Results also showed that a consecutive treatment that incorporates an initial hydrolysis by cellulolytic enzymes followed by a subsequent treatment by amylolytic treatment yielded reducing sugars of 0.64g per gram of milled cassava peels. A reverse treatment where the cellulolytic enzymes were used to first treat the peels before a second treatment by amylolytic enzymes yielded 0.61g reducing sugar per gram of milled cassava peels. A simultaneous hydrolysis by both cellulolytic and amylolytic enzymes produced a maximum reducing sugar of 0.58g per gram of milled cassava peels. A modification that incorporates hot water pretreatment, simultaneous and consecutive treatment was carried out. The milled cassava peels treated with hot water at 1000C and amylase enzymes for 2 hours were further subjected to a simultaneous saccharification by cellulases and glucoamylase enzymes yielded a reducing sugar of 0.62g per gram of peels. Fermentation experiments were also carried out with Kluyveromyces marxianus at 400C and results showed a maximum ethanol yield of 0.12g ethanol per g of cassava peels for a separate hydrolysis and fermentation process and 0.18g ethanol per g of cassava peels for the simultaneous saccharification and fermentation process. It was concluded that cassava peels presents a very good source of sugars for bioethanol production

L-(+)-Lactic Acid from Reed: Comparing Various Resources for the Nutrient Provision of B. coagulans

Biotechnological production of lactic acid (LA) is based on the so-called first generation feedstocks, meaning sugars derived from food and feed crops such as corn, sugarcane and cassava. The aim of this study was to exploit the potential of a second generation resource: Common reed (Phragmites australis) is a powerfully reproducing sweet grass which grows in wetlands and creates vast monocultural populations. This lignocellulose biomass bears the possibility to be refined to value-added products, without competing with agro industrial land. Besides utilizing reed as a renewable and inexpensive substrate, low-cost nutritional supplementation was analyzed for the fermentation of thermophilic Bacillus coagulans. Various nutritional sources such as baker’s and brewer’s yeast, lucerne green juice and tryptone were investigated for the replacement of yeast extract. The structure of the lignocellulosic material was tackled by chemical treatment (1% NaOH) and enzymatic hydrolysis (Cellic® CTec2). B. coagulans DSM ID 14-300 was employed for the homofermentative conversion of the released hexose and pentose sugars to polymerizable L-(+)-LA of over 99.5% optical purity. The addition of autolyzed baker’s yeast led to the best results of fermentation, enabling an LA titer of 28.3 g L−1 and a yield of 91.6%