Feedstock For Bioethanol Production Research Articles

A KINETIC STUDY OF ENZYMATIC HYDROLYSIS OF OIL PALM BIOMASS FOR FERMENTABLE SUGAR USING POLYETHYLENE GLYCOL (PEG) IMMOBILIZED CELLULASE

In this work, enzymatic hydrolysis by cellulase in a soluble and an immobilized form was studied to convert lignocellulosic oil palm empty fruit bunch (EFB) biomass into fermentable sugars as a feedstock for bioethanol production. The cellulase was covalently immobilized with activated and functionalized polyethylene glycol (PEG) via glutaraldehyde coupling method. As a whole, the immobilized cellulase displayed 50% higher efficiency over free cellulase, in reducing sugar recovery during hydrolysis reactions at pH of 4.8 and temperature of 50°C. From the kinetic study, it showed that Michaelis constant (Km) and limiting velocity (Vmax) of immobilized cellulase were 179.2 mg/ml and 33.5 mg/ml.min respectively, comparable with the value for free cellulose, 171.8 mg/ml and 34.5 mg/ml.min respectively. This result could be attributed to the effect of PEG on the binding cellulase to substrate desorb substrates, and enables free interaction of cellulase to hydrolyse cellulose maximally

Nitrogen explosion pretreatment of lignocellulosic material for bioethanol production

ABSTRACTA novel method for the pretreatment of lignocellulosic material is investigated in this work, using floodplain meadow hay as a feedstock for bioethanol production. Pressurized nitrogen (N2) pretreatment is combined with explosive decompression to achieve high glucose yields with simple technology and low energy input. Results show that N2 explosion yields hydrolysis efficiencies up to 71.8%. The highest hydrolysis efficiency was achieved at a temperature of 210°C with a cellulose to glucose conversion rate of 195.1 g kg−1 of biomass.

Sequential Thermochemical Hydrolysis of Corncobs and Enzymatic Saccharification of the Whole Slurry Followed by Fermentation of Solubilized Sugars to Ethanol with the Ethanologenic Strain Escherichia coli MS04

Interest in the use of corncobs as feedstock for bioethanol production is growing. This study assesses the feasibility of sequential thermochemical diluted sulfuric acid pretreatment of corncobs at moderate temperature to hydrolyze the hemicellulosic fraction, followed by enzymatic hydrolysis of the whole slurry, and fermentation of the obtained syrup. The total sugar concentration after enzymatic hydrolysis was 85.21 g/l, i.e., 86 % of the sugars were liberated from the polymeric fractions, together with a low amount of furfural (0.26 g/l) and 4.01 g/l of acetic acid. The syrups, which contained 36.3, 40.9, 4.47, and 1.84 g/l of xylose, glucose, arabinose, and mannose, respectively, were fermented (pH 7, 37 °C, 150 rpm) to ethanol with the metabolically engineered acetate-tolerant Escherichia coli strain MS04 under non-aerated conditions, producing 35 g/l of ethanol in 18 h (1.94 gEtOH/l/h), i.e., a conversion yield greater than 80 % of the theoretical value based on total sugars was obtained. Hence, using the procedures developed in this study, 288 l of ethanol can be produced per metric ton of dry corncobs. Strain MS04 can ferment sugars in the presence of acetate, and the amount of furans generated during the sequential thermochemical and enzymatic hydrolysis was low; hence, the detoxification step was avoided. The residual salts, acetic acid, and solubilized lignin present in the syrup did not interfere with the production of ethanol by E. coli MS04 and the results show that this strain can metabolize mixtures of glucose and xylose simultaneously.

Natural variation in the glucose content of dilute sulfuric acid-pretreated rice straw liquid hydrolysates: implications for bioethanol production.

Rice straw is a promising resource for bioethanol production. Because the glucose content of pretreatment liquid hydrolysates is highly correlated with ethanol yield, the selection of appropriate rice cultivars is essential. The glucose content in liquid hydrolysates of pretreated rice straws of 208 diverse cultivars was evaluated in natural field in 2013 and 2014 using a novel high-throughput system. The glucose content of the rice straw samples varied across cultivars and was affected by environmental factors such as temperature and solar radiation. Several high-quality cultivars exhibiting high glucose content in both years were identified. The results of this study can aid in development of novel rice cultivars suitable as both feedstocks for bioethanol production and cooking.

Multistage process for the production of bioethanol from almond shell

This work describes the feasibility of using almond shell as feedstock for bioethanol production. A pre-treatment step was carried out using 4% NaOH for 60min at 121°C followed by 1% sulfuric acid for 60min at 121°C. Enzymatic saccharification of the pre-treated almond shell was performed using Penicillium occitanis enzymes. The process was optimized using a hybrid design with four parameters including the incubation time, temperature, enzyme loads, and polyethylene glycol (PEG) concentration. The optimum hydrolysis conditions led to a sugar yield of 13.5%. A detoxification step of the enzymatic hydrolysate was carried out at pH 5 using 1U/ml of laccase enzyme produced by Polyporus ciliatus. Fermenting efficiency of the hydrolysates was greatly improved by laccase treatment, increasing the ethanol yield from 30% to 84%. These results demonstrated the efficiency of using almond shell as a promising source for bioethanol production.

Sap from various palms as a renewable energy source for bioethanol production

Sap is a watery fluid that transports plant photosynthetic products towards various tissues to support growth. Tapping palms for their sap is reported to have originated from India approximately 4,000 years ago. Palm sap is rich in sugars with some inorganics and nutrients, which are attractive components for bioethanol production. Based on advances and current knowledge on the availability, collection, yield, and exploitation of various palm saps, this article evaluates their potential and sustainability as feedstocks for bioethanol production.

Inhibitory effect of Eucalyptus globulus pretreated liquors on bioethanol production from Zymomonas mobilis NRRL B-806

ABSTRACTLignocellulosic wastes from agriculture are potentially useful as a low cost feedstock for production of bioethanol. During pretreatment of lignocellulosic materials, a wide range of inhibitory compounds to microorganisms are formed or released. The present work focused on production of bioethanol by Z. mobilis NRRL B-806 in different culture media. Inhibitory effects of the bio-products yielded in the pretreatment process of Eucalyptus globulus were determined. Results obtained showed that maximum bioethanol production yield YE/S for Z. mobilis NRRL B-806 was 87%. Ethanol production and glucose consumption were clearly affected by high inhibitors concentration present in pretreated liquors obtained by auto-hydrolysis.

Enzymatic saccharification of high pressure assist-alkali pretreated cotton stalk and structural characterization

Cotton stalk is a potential biomass for bioethanol production, while the conversion of direct saccharification or biotransformation of cotton stalk is extremely low due to the recalcitrant nature of lignocellulose. To enhance the enzymatic conversion of cotton stalks, the enzymatic saccharification parameters of high pressure assist-alkali pretreatment (HPAP) cotton stalk were optimized in the present study. Results indicated that a maximum reducing sugar yield of 54.7g/100g dry biomass cellulose was achieved at a substrate concentration of 2%, 100rpm agitation, 0.6g/g enzyme loading, 40°C hydrolysis temperature, 50h saccharification time, and pH 5.0. Scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectroscopy were used to identify structural changes in native, pretreated biomass and hydrolyzed residues. Structural analysis revealed large part of amorphous cellulose and partial crystalline cellulose in the HPAP cotton stalk were hydrolyzed during enzymatic treatment. HPAP cotton stalk can be used as a potential feed stock for bioethanol production.

Phosphoric acid pretreatment of Achyranthes aspera and Sida acuta weed biomass to improve enzymatic hydrolysis

Achyranthes aspera and Sida acuta, two types of weed biomass are abundant and waste in Thailand. We focus on them as novel feedstock for bio-ethanol production because they contain high-cellulose content (45.9% and 46.9%, respectively) and unutilized material. Phosphoric acid (70%, 75%, and 80%) was employed for the pretreatment to improve by enzymatic hydrolysis. The pretreatment process removed most of the xylan and a part of the lignin from the weeds, while most of the glucan remained. The cellulose conversion to glucose was greater for pretreated A. aspera (86.2±0.3%) than that of the pretreated S. acuta (82.2±1.1%). Thus, the removal of hemicellulose significantly affected the efficiency of the enzymatic hydrolysis. The scanning electron microscopy images showed the exposed fibrous cellulose on the cell wall surface, and this substantial change of the surface structure contributed to improving the enzyme accessibility.

Yellow Laccase-Mediated Lignin Degradation of Ricinus communis: A Future Agricultural Biomass for Biofuel Production

Agricultural biomass left to decay in the fields and forests has a huge possibility to serve as a low-cost feedstock for production of bioethanol and other value added products. In the Indian subcontinent, Ricinus communis, growing in parched conditions contributes a major biomass containing 44.4 % cellulose, 22.8 % hemicelluloses and 19.8 % lignin. In the present study, response surface methodology based on central composite design and genetic algorithm has been used to explore the effects of pH, temperature, solid-to-liquid ratio (w/v), enzyme activity, and incubation time on enzymatic depolymerization of R. communis. The maximum delignification obtained was 86.7 %. Delignified biomass was characterized by Fourier transformed infrared spectroscopy and scanning electron microscopy. Lignin degradation products were identified by gas chromatography—mass spectroscopy. Cinnamic acid, p-coumaric acid (4-hydroxycinnamic acid), and ferulic acid (4-hydroxy-3-methoxycinnamic acid) were detected in the extract degraded by yellow laccase.

Development of China’s biofuel industry and policy making in comparison with international practices

Bioethanol and biodiesel are the main biofuels produced in the industrial scale. Research into bioethanol in China began around 1930, whereas biodiesel was not investigated as a biofuel until 1980. The Renewable Energy Law of the People’s Republic of China, which took effect on 1 January 2006, was perhaps the most important decree aimed at promoting the development and utilization of renewable energy. Current bioethanol production in China uses 10 % of the corn production in the north-eastern and northern provinces (Jilin, Liaoning, Heilongjiang, Hebei and Henan) as the feedstock (Fig. 1). When the aged grain was exhausted by the end of 2004, edible grain had to be used as the feedstock for bioethanol production. Nevertheless, production remains relatively low as only 0.71 % of the country’s grain (3.366 million tons of grain) was used for production of 1.32 million tons of bioethanol in 2006. However, due to the fact that 70 % of grain was used for feeding animals, concern was raised over potential conflicts between the demand for animal food and the demand for fuel. This led to a rise in crop prices in late 2006. Apart from grain, cassava, sugar cane, Jerusalem artichoke, sweet potato and lignocellulose from crop straw/ stalk and forestry residues might also be used as the feedstock. China’s first cassava bioethanol project, which has an annual capacity of 200,000 tons, was started in Beihai City of Guangxi Zhuang Autonomous Region in 2007 (Fig. 1). Experimental production capacity of 10,000 tons of cellulose-based ethanol and a feedstock conversion rate of over 18 % have been reported [1]. Because of the increasing financial support for the development of a cellulose-based ethanol industry and the reduction in related taxes or fees by the government, emphasis on cellulose-based ethanol is likely to become an inevitable trend in China’s bioethanol industry. Currently, biodiesel production plants in China are usually small-scaled, producing 100–20,000 tons and usually operating for only a few months in the year due to lack of sufficient supply of feedstock. At present, almost all biodiesel is sourced from animal fat or waste vegetable oil from oil crushing plants or restaurants [2]. However, due to high demand from animal feed or other chemical processing sectors, the price for these feedstocks is often too high for biodiesel production. In June 2011, China’s Ministry of Finance and the State Administration of Taxation jointly issued a notice that temporarily removes the 5 % consumption tax for biodiesel producers who used cooking oil that is not allowed for human consumption, non-edible lipid from the animal slaughtering houses, etc. This may help to ease the constraints on the biodiesel industry. Moreover, to supply the feedstock of biodiesel, the State Forestry Administration plans to develop 800,000 ha of oleaginous nut-bearing plants, principally in Sichuan, Yunnan, Guizhou, Chongqing, Hebei, Shanxi, Anhui, Henan, Hubei and Jiangxi, by 2015. The trees could eventually produce 6 million tons of biodiesel (China bio-fuels industry analysis, 2009). Besides the edible oilseed, other potential inputs include rapeseeds, Jatropha nuts, switch grass, sunflower seeds, Chinese pistachio, peanuts, sesame seeds, Barbados nuts, Fufang vines, Yousha bean and Chinese dogwood nuts. A considerable amount of assistance has been provided to increase the production capacity of the biofuel industry worldwide in the form of grants or loans. Some of this assistance has been provided by energy ministries and J. Zhao (&) Bureau of Academic Divisions, Chinese Academy of Sciences, Beijing 100190, China e-mail: zhaojun@cashq.ac.cn

Enhanced fermentable sugar production from kitchen waste using various pretreatments

The kitchen waste fraction in municipal solid waste contains high organic matter particularly carbohydrate that can contribute to fermentable sugar production for subsequent conversion to bioethanol. This study was carried out to evaluate the influence of single and combination pretreatments of kitchen waste by liquid hot water, mild acid pretreatment of hydrochloric acid (HCl) and sulphuric acid (H2SO4) and enzymatic hydrolysis (glucoamylase). The maximum total fermentable sugar produced after combination pretreatment by 1.5% HCl and glucoamylase consisted of 93.25 g/L glucose, 0.542 g/L sucrose, 0.348 g/L maltose, and 0.321 g/L fructose. The glucose released by the combination pretreatment method was 0.79 g glucose/g KW equivalent to 79% of glucose conversion. The effects of the pre-treatment on kitchen waste indicated that the highest solubilization was 40% by the combination method of 1.5% HCl and glucoamylase. The best combination pre-treatment gave concentrations of lactic acid, acetic acid, and propionic acid of 11.74 g/L, 6.77 g/L, and 1.02 g/L, respectively. The decrease of aliphatic absorbance bands of polysaccharides at 2851 and 2923 cm-1 and the increase on structures of carbonyl absorbance bands at 1600 cm-1 reflects the progress of the kitchen waste hydrolysis to fermentable sugars. Overall, 1.5% HCl and glucoamylase treatment was the most profitable process as the minimum selling price of glucose was USD 0.101/g kitchen waste. Therefore, the combination pretreatment method was proposed to enhance the production of fermentable sugar, particularly glucose from kitchen waste as the feedstock for bioethanol production.

Bioethanol Production from Eucalyptus camaldulensis Wood Waste Using Bacillus subtilis and Escherichia coli Isolated from Soil in Afaka Forest Reserve, Kaduna State Nigeria

The economic and ecological problems associated with fossil fuel have raised interest in biofuel research in recent times in different parts of the world. The use of Eucalyptus forest waste biomass with no appreciable value to industries or for food as alternative and cost effective feedstock for bioethanol production was evaluated in this study. E. camaldulensis biomass (bark and leaves) were pretreated separately with acid (2M H2SO4) and Microwave irradiation (250V, 50Hz) prior to fermentation with Bacillus subtilis and Escherichia coli isolated from surrounding soil. Higher yield of reducing sugar were obtained from bark (43 %) and leaves (38.5 %) pretreated by microwave irradiation as compared with acid treated plant biomass. Similarly, Bioethanol volume and concentration of 34.89 g/l and 0.51 % respectively were higher in Microwave irradiated bark of E. camaldulensis at 21 days of fermentation when E. coli and B. subtilis were used in synergy The least bioethanol volume yield of 18.79 g/l and concentration of 0.12 % when bark and leaves of E. camaldulensis were combined was obtained on day 7 of fermentation using E. coli. The study concludes that the amount of dried wastes generated (37.8 kg) from one average stand of Eucalyptus tree could yield significant volume (131,884.2 g/l) of bioethanol when B. subtilis and E. coli are used in synergy.

Bioethanol Production from Indica IR.64 Rice Straw Biomass by Direct Saccharification and Fermentation

Lignocellulosic substances such as agricultural wastes are attractive feed stocks for bioethanol production. Indica IR.64 rice straw is one of abundant agricultural wastes in Indonesia and could be used to bioethanol production. It has several characteristics such as high content of cellulose and hemicelluloses that can be readily hydrolyzed into fermentable sugars. A simple process (the direct saccharification and fermentation process) to produce ethanol from rice straw was developed in order to establish an efficient bioethanol production. In this work, no harsh pre-treatment steps were applied and also use a simple one-vat reactor without the risk of losing liberated carbohydrate. The first step in using rice straw for bioethanol production is size reduction through milling and sieving process prior to enzymatic hydrolysis. Direct saccharification and fermentation (DSF) of Indica IR.64 rice straw was examined and compared with two type of control (systems devoid of yeast and enzyme). The experiment were carried out under anaerobic condition, where the cellulase crude enzyme and cellulosic substrates (rice straw) produced glucose from the cellulose and Saccharomyces cerevisiae directly assimilated the glucose to bioethanol. The faster rate of bioethanol production during DSF by S accharomyces cerevisiae was obtained within the first 12h. The maximum ethanol concentration, ethanol yield, and theoretical ethanol yield of untreated rice straw were 0.25 g/L, 10 and 14.88%, respectively. Nevertheless, the direct saccharification and fermentation shows the potential for lower cost and higher efficiency for bioethanol production.

Sugarcane Biomass Production in South Florida: A Comparative Emergy Assessment of Organic Soil and Mineral Soil Production Systems

An Emergy Assessment (EMA) of sugarcane cultivation as feedstock for bioethanol production in South Florida was performed to develop a sustainability profile of the farming systems. In this study, a sugarcane farming system on muck soil (organic soil) was compared with a similar cropping system on a sandy soil (mineral soil). The study provides a comparison of these alternative systems from the perspective of their resource use, environmental impact and sustainability. The representative farm for both systems was based on a 5000 acre farm assumed to be already established in South Florida. Emergy analysis was applied to evaluate environmental support required for the sugarcane production in both systems. In line with the methodology a quantitative inventory of free natural resources and purchased input flows into the systems was created. The results showed that aside ground water irrigation which dominates (44%) in both systems, the largest emergy flows for biofuel production on organic soil were associated with soil erosion or subsidence (19%), labor (12%), evapotranspiration (11%), and fuel (8%). However, for sandy soil production, the main contributors were lime (13%), labor (12%), and fuel (8%). The emergy analysis suggests that due to the non-renewability of soil loss in the organic soil farming system, a reduction in the purchased inputs for sandy (mineral) soils based on alternative farming measures potentially makes mineral soil sugarcane ethanol production a rather more sustainable and attractive alternative for a better environmental performance.

Potential Thai grasses for bioethanol production

Use of lignocellulosic biomass, such as wild grasses, represents a more sustainable alternative to food stocks for the creation of fuel bioethanol. There are numerous types of wild grasses grown naturally in Thailand that can be used as a feedstock for bioethanol production and several of them have been examined already for their physical characteristics and ethanol production potential. Physical characteristics such as a high dry matter yield and high percentage of cellulose make Tifton Bermuda grass a particularly attractive candidate for bioethanol production. The different studies examined in this paper used differing pretreatment methods on various types of wild grasses with varying levels of success depending on the method and grass used. The largest amount of ethanol produced per initial gram of grass was 0.14 g per gram from two separate types of vetiver grasses, likely due to a utilization of both a glucose and xylose-fermenting organism during fermentation. For any particular wild Thai grass to be used in the future as a feedstock for bioethanol production, it is essential that more research be done to optimize the process of pretreatment and fermentation.

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 Accumulation of Carbohydrate and Starch in Chlorella zofingiensis Induced by Nitrogen Starvation

Though less attention has been paid to microalgae as a feedstock for bioethanol production, many microalgae seem to have this potential since they contain no lignin, minor hemicellulose, and abundant carbohydrate. The objective of this study was to investigate the effect of nitrogen starvation on carbohydrate and starch accumulation in green microalga Chlorella zofingiensis and assess the feasibility of using this microalga as a bioethanol feedstock. The results showed that the specific growth rate under nitrogen starvation (0.48 day(-1)) was much lower than that under nitrogen repletion (1.02 day(-1)). However, nitrogen starvation quickly induced the accumulation of carbohydrate, especially starch. After merely 1 day of nitrogen starvation, carbohydrate and starch increased 37 % and 4.7-fold, respectively. The highest carbohydrate content reached 66.9 % of dry weight (DW), and 66.7 % of this was starch. In order to obtain enough carbohydrate productivities for bioethanol production, two-stage cultivation strategy was implemented and found to be effective for enhancing biomass, carbohydrate, and starch simultaneously. The optimal biomass, carbohydrate, and starch productivities of C. zofingiensis were obtained after 5 days of cultivation, and their values were 699, 407, and 268 mg L(-1) day(-1), respectively.

Isolation, characterization and plant growth promotion effects of putative bacterial endophytes associated with sweet sorghum (Sorghum bicolor (L) Moench)

Sweet sorghum (Sorghum bicolor) is cultivated in Uruguay in complementation with sugarcane (Saccharum officinarum) as a feedstock for bioethanol production. It requires the application of high levels of chemical fertilizer for optimal growth, which causes environmental degradation. Plant growth-promoting (PGP) bacteria are of biotechnological interest since they can improve the growth of several important agronomical crops. Of particular interest are endophytes, which are those bacteria that can be detected at a particular moment within the internal tissues of healthy plants from where they can promote their growth. The aims of this work were to isolate and characterize, as well as identify putatively endophytic bacteria associated with sweet sorghum (cv-M81E), and also to study the inoculation effects of selected isolates on sorghum growth. A collection of 188 putative endophytes from surface-sterilized stems and roots was constructed and characterized. Bacterial isolates were shown to belong to different genera including Pantoea, Enterobacter, Pseudomonas, Acinetobacter, Stenotrophomonas, Ralstonia, Herbaspirillum, Achromobacter, Rhizobium, Chryseobacterium, Kocuria, Brevibacillus, Paenibacillus, Bacillus and Staphylococcus. PGP and infection features were investigated in vitro, and revealed some promising biotechnological candidates. In addition, isolates UYSB13 and UYSB45 showed PGP effects in greenhouse assays. This work provides the basis for further studies under field conditions, with the final aim of developing an effective inoculant for sorghum.

The usage of carrot pomace as a feedstock for bioethanol production

The usage of carrot pomace as a feedstock for bioethanol production