Sweet sorghum and Miscanthus：Two potential dedicated bioenergy crops in China

Among the potential non-food energy crops,the sugar-rich C4 grass sweet sorghum and the biomass-rich Miscanthus are increasingly considered as two leading candidates.Here,we outline the biological traits of these energy crops for largescale production in China.We also review recent progress on understanding of plant cell wall composition and wall polymer features of both plant species from large populations that affect both biomass enzymatic digestibility and ethanol conversion rates under various pretreatment conditions.We finally propose genetic approaches to enhance biomass production,enzymatic digestibility and sugar-ethanol conversion efficiency of the energy crops.

Optimization of rice wine fermentation process based on the simultaneous saccharification and fermentation kinetic model

Chinese rice wine making is a typical simultaneous saccharification and fermentation(SSF) process.During the fermentation process,temperature is one of the key parameters which decide the quality of Chinese rice wine.To optimize the SSF process for Chinese rice wine brewing,the effects of temperature on the kinetic parameters of yeast growth and ethanol production at various temperatures were determined in batch cultures using a mathematical model.The kinetic parameters as a function of temperature were evaluated using the software Origin8.0.Combing these functions with the mathematical model,an appropriate form of the model equations for the SSF considering the effects of temperature were developed.The kinetic parameters were found to fit the experimental data satisfactorily with the developed temperature-dependent model.The temperature profile for maximizing the ethanol production for rice wine fermentation was determined by genetic algorithm.The optimum temperature profile began at a low temperature of 26 °C up to 30 h.The operating temperature increased rapidly to 31.9 °C,and then decreased slowly to 18 °C at 65 h.Thereafter,the temperature was maintained at18 °C until the end of fermentation.A maximum ethanol production of 89.3 g·L^(-1)was attained.Conceivably,our model would facilitate the improvement of Chinese rice wine production at the industrial scale.

Simultaneous saccharification and fermentation of steam-pretreated lespedeza stalks for the production of ethanol

Lespedeza stalks were subjected to steam pretreatment at 210℃ for some steaming time before simultaneous saccharification and fermentation （SSF）. Cellulose-derived glucose was extensively utilized by yeast during SSE The ethanol yields after steam pretreatment of the lespedeza stalks at 210℃ were 59.3%, 72.8% and 62.2% of the theoretically expected values when the steaming times were 2, 4 and 6 min, respectively. The highest yield from α-cellulose was 92.7% of the theoretical value. Steam explosion pretreatment of lespedeza stalks increased ethanol yields by a factor of 4.4, from 16.4% （untreated） to 72.8% （steam explosion pretreated）.

Lactic Acid Fermentation from Coffee Ground Waste Hydrolysate by Lactobacillus rhamnosus

Lactic acid is an important organic acid that is widely used in the food,pharmaceutical,and cosmetic industries.Lactic acid was produced from coffee ground waste which contains fermentable sugars and is increasingly generated from our daily dietary life.Among 114 strains of Lactobacillus species,Lactobacillus rhamnosus ATCC 10863 was selected for the production of lactic acid from coffee ground waste.Through alkali pretreatment and saccharification,cellulose and hemicellulose in coffee ground waste were converted into fermentable sugars.Pretreatment experiments were conducted at various alkali solution,concentrations,and times.Alkali pretreatment with 35 g/L of KOH at 121oC for 60 min,the highest concentration of fermentable sugars was produced.The optimum concentration of Viscozyme L was 2%when saccharification was proceeded at 55oC for 7 days.The productivity of lactic acid fermentation was the highest(0.59 g/L/h)at 100 g of coffee ground waste(1x concentration),whereas the lactic acid concentration was the highest at 600 g of coffee ground waste(6x concentration).As the concentration of coffee ground increased,the lactic acid concentration was also increased,however,the amount was not proportional to the coffee ground waste used.In this study,it was found that coffee ground waste could be used as a culture medium for Lactobacillus rhamnosus ATCC 10863 through pretreatment and saccharification for the production of lactic acid.

Microwave-Assisted Alkaline Pretreatment and Microwave Assisted Enzymatic Saccharification of Oil Palm Empty Fruit Bunch Fiber for Enhanced Fermentable Sugar Yield

Lignocellulosic materials are promising alternative feedstocks for bioethanol production. However, the recalcitrant nature of lignocellulosic biomass necessitates an efficient pretreatment pretreatment step to improve the yield of fermentable sugars and maximizing the enzymatic hydrolysis efficiency. Microwave pretreatment may be a good alternative as it can reduce the pretreatment time and improve the enzymatic activity during hydrolysis. The overall goal of this paper is to expand the current state of knowledge on microwave-based pretreatment of lignocellulosic biomass and microwave assisted enzymatic reaction or Microwave Irradiation-Enzyme Coupling Catalysis (MIECC). In the present study, a comparison of microwave assisted alkali pretreatment was tried using Oil Palm empty fruit bunch. The microwave assisted alkali pretreatment of EFB using NaOH, significantly improved the enzymatic saccharification of EFB by removing more lignin and hemicellulose and increasing its accessibility to hydrolytic enzymes. The results showed that the optimum pretreatment condition was 3% (w/v) NaOH at 180 W for 12 minutes with the optimum component loss of lignin and holocellulose of about 74% and 24.5% respectively. The subsequent enzymatic saccharification of EFB pretreated by microwave assisted NaOH (3% w/v);resulted in 411 mg of reducing sugar per gram EFB at cellulose enzyme dosage of 20 FPU. The overall enhancement by the microwave treatment during the microwave assisted alkali pretreatment and microwave assisted enzymatic hydrolysis was 5.8 fold. The present study has highlighted the importance of well controlled microwave assisted enzymatic reaction to enhance the overall reaction rate of the process.

Effect of Enzymes on the Quality of Beer/Wort Developed from Proportions of Sorghum Adjuncts

The effect of commercial enzymes on quality of wort developed from replacement of malted barley (100%) with sorghum as adjunct 50%, 60%, 70%, and 80% was investigated for pH, colour, filteration rate, extract asin, dry extract, viscosity, total soluble nitrogen and free amino nitrogen. The wort pH (5.6 - 6.0) is relatively stable with no significant changes at all levels of replacements. The colour is lighter with increment in proportion of the sorghum as it appears as colour diluents. Wort filteration rate is reduced with the sorghum replacement and the wort produced tends to be turbid which affects the utilization of the wort. The total soluble nitrogen and free amino nitrogen value increased with the use of commercial enzymes while the viscosity decreases with enzymes. The use of ceremix and cereflo have been found to be relatively more effective in the preparation of beer wort as observed for the result obtained in proportions of sorghum and malt barley. The use of high percentage sorghum as adjunct with commercial enzymes are found to be useful in production of high quality wort with low cost and profitability.

Wood forming tissue-specific expression of PdSuSy and HCHL increases holocellulose content and improves saccharification in Populus

Development of strategies to deconstruct lignocellulosic biomass in tree species is essential for biofuels and biomaterials production.We applied a wood forming tissue-specific system in a hybrid poplar to express both PdSuSy(a sucrose synthase gene from Populus deltoides×P.euramericana that has not been functionally characterized)and HCHL(the hydroxycinnamoyl-CoA hydratase-lyase gene from Pseudomonas fluorescens,which inhibits lignin polymerization in Arabidopsis).The PdSuSy-HCHL overexpression poplars correspondingly driven by the promoters of Arabidopsis AtCesA7 and AtC4 H resulted in a significant increase in cellulose(>8%),xylan(>12%)and glucose(>29%)content,accompanying a reduction in galacturonic acid(>36%)content,compared to control plants.The saccharification efficiency of these overexpression poplars was dramatically increased by up to 27%,but total lignin content was unaffected.These transgenic poplars showed inhibited growth characteristics,including>16%reduced plant height,>10% reduced number of internodes,and>18% reduced fresh weight after growth of 4 months,possibly due to relatively low expression of HCHL in secondary xylem.Our results demonstrate the structural complexity and interaction of the cell wall polymers in wood tissue and outline a potential method to increase biomass saccharification in woody species.

Research on the Conditions of Enzymatic Saccharification for Sugarcane Bagasse

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Effects of formaldehyde on fermentable sugars production in the low-cost pretreatment of corn stalk based on ionic liquids

Low cost processing of lignocellulosic biomass is of great importance for sustainable chemistry and engineering.Herein,a low cost system composed of 1-butyl-3-methylimidazolium chloride([C_(4)C_(1) im]Cl),HCl and formaldehyde(FA)was developed for the pretreatment of corn stalk at 80℃.The efficiency of this technology was compared with that in dioxane system or without FA addition.Due to FA stabilization,the extent of acid-hydrolysis of carbohydrate fraction can be significantly decreased while 70%above of lignin was removed with the pretreatment of[C_(4)C_(1) im]Cl/HCl/FA system at 80℃for 2 h.A maximum reducing sugar yield of 93.7%and glucose concentration of 7.0 mg·ml^(-1) were subsequently obtained from enzymatic hydrolysis of the slurry.There were great differences in compositions of small molecule degraded products obtained with FA addition or not.The present[C_(4)C_(1) im]C_(l) based system exhibits great potential of substituting volatile organic solvents(i.e.dioxane)in developing low cost lignocellulosic biomass pretreatment at low temperature.Also,this work would gain insight into understanding on the roles of stabilization methods on the economic improvement of IL based biomass processing.

Fuelization of Italian Ryegrass and Napier Grass through a Biological Treatment and Photocatalytic Reforming

Fuelization of Italian ryegrass and Napier grass was examined by the combination of biological treatments and photocatalytic reforming (photo-Reform). The alkali-pretreated Italian ryegrass and Napier grass were subjected to the enzymatic saccharification using cellulase and xylanase. Xylose and glucose were produced in 56.6% and 71.1% from Italian ryegrass and in 49.5% and 67.3% from Napier grass, respectively. Xylose and glucose were converted to hydrogen by the photo-Reform using a Pt-loaded titanium oxide (Pt/TiO2) under UV irradiation. Moreover, a low-moisture anhydrous ammonia (LMAA) pretreatment was performed for Italian ryegrass and Napier grass by keeping moist powdered biomass under NH3 gas atmosphere at room temperature for four weeks. The Italian ryegrass and Napier grass which were pretreated by LMAA method were subjected to simultaneous saccharification and fermentation (SSF) using a mixture of cellulase and xylanase as well as Saccharomyces cerevisiae in acetate buffer (pH 5.0). Ethanol and xylose were produced in 91.6% and 51.6% from LMAA-pretreated Italian ryegrass and 78.6% and 68.8% from Napier grass, respectively. After the evaporation of ethanol, xylose was converted to hydrogen by the photo-Reform. In the case of saccharification→photo-Reform, energy was recovered as hydrogen from the alkali-pretreated Italian ryegrass and Napier grass in 71.9% and 77.0% of energy recovery efficiency, respectively. In the case of SSF→photo-Reform, the energy was recovered in 82.7% and 77.2% as ethanol and hydrogen from the LMAA-pretreated Italian ryegrass and Napier grass, respectively.

Optimization Studies in Simultaneous Saccharification and Fermentation of Wheat Bran Flour into Ethanol

The effects of process variables in Simultaneous Saccharification and Fermentation (SSF) of wheat bran flour were studied in bulk fermentation using a coculture of Aspergillus niger - Kluveromyces marxianus. The effect of substrate density, pH, temperature, and enzyme concentration on wheat bran was predicted by designing experiments in which a single parameter is varied keeping other variables at a constant level. The above parameters were optimized for a batch culture in a fermentor. Optimal values for substrate concentration, pH, temperature, and enzyme concentration during processing were 200 g/l, 5.5, 65°C, and 7.5 IU, respectively. In pre-treatment experiments, the concentration of enzymes and the pre-treatment temperature are highly correlated. The influence of pH, temperature, and substrate density on ethanol production was investigated. Temperature pH was determined as optimal, 32°C and 5.5, respectively. After 48 hours of fermentation at optimum pH, a solution of wheat bran containing a maximum of 6% starch produces a maximum of 22.9 g/l ethanol.

Feasibility Study of Ethanol Production from Food Wastes by Consolidated Continuous Solid-State Fermentation

To save the cost and input energy for bioethanol production, a consolidated continuous solid-state fermentation (CCSSF) system composed of a rotating drum reactor, a humidifier and a condenser has been developed. In this research, the feasibility of using this system for production of ethanol from food wastes was carried out. The ethanol conversion of bread crust and rice grain (uncooked rice) as substrates reached up to 100.9% ± 5.1% and 108.0% ± 7.9% (against theoretical yield), respectively. Even for bread crust, a processed starchy material which contained lower carbohydrate content than rice grain, the amount of ethanol obtained in a unit of CCSSF per year was higher due to easy saccharification and fermentation. The salt contained in potato chips directly affected yeast activity resulting to low ethanol conversion (80.7% ± 4.7% against theoretical yield).

Development of Highly Digestible Grain Sorghum Lines Suitable for Efficient Dry-Grind Ethanol Production

Low-world oil prices but supportive government policies provide growing environmental and energy security support favorable for the bioethanol market. The need to generate large and sustainable supply of biomass to make bioethanol will require the development of crops grown specifically for bioenergy production. Given the existing history of genetic improvement and infrastructure available for sorghum, (Sorghum bicolor L. Moench) hybrids will be one of the several species dedicated as energy crop and the subject of this study. Texas A & M University Sorghum Breeding Program has developed hybrid sorghum varieties with high protein digestibility and improved starch digestibility. Most of the previous research on grain sorghum focused on the digestibility of sorghum protein from the nutritional point of view. The aim of the current study was to select best sorghum lines from? relatively large and diverse sorghum samples that breeders are currently working with for the development of new low energy input liquefaction, saccharification and fermentation methodologies to produce bioethanol. Limited researches studies report on the performance of sorghum varieties in ethanol fermentation in relation to the protein and starch digestibility of sorghum.

Optimal Method for Production of Amorphous Cellulose with Increased Enzymatic Digestibility

In this paper,a simple and cheap method for producing of amorphous cellulose was studied by treating the initial cellulosic material(MCC and waste paper)with a cold solvent,such as aqueous solution of 7%NaOH/12%Urea,at the various ratios of the solvent to cellulose(v/w)(R).If was found that after treatment of cellulose materials with the solvent at R≥5,a completely amorphous cellulose(AC)is formed.Due to high digestibility,the AC with concentration of 50 g/L is converted to glucose almost completely for 48 h under the action of cellulolytic enzyme CTec-3 with a dose of 30 mg/g solid sample.Such sample can be used as an amorphous standard in the study of crystallinity degree and enzymatic hydrolysis of various types of cellulose and lignocellulose.It was found that enzymatic saccharification is most advantageous to carry out at elevated concentrations of AC,150 g/L.Due to high cost of MCC,it is preferable to use a cheap cellulose raw material,such as mixed waste paper(MWP),for the commercial production of AC and glucose.The resulting glucose can find application in biotechnology as a promising nutrient for various microorganisms.

Process Research on Separate Hydrolysis and Fermentation(SHF) and Simultaneous Saccharification and Fermentation(SSF) of Ethanol Production by Lignocellulose

[ Objective] The research aimed to explore the efficiency of ethanol production under the optimal conditions of separate hydrolysis and fermentation （SHF） and simultaneous saccharification and fermentation （SSF）. [ Method ] Under the optimal conditions of hydrolysis and fermenta- tion, SHF and SSF process were designed respectively. SHF process was conducted under the optimal conditions of hydrolysis and fermentation separately, while SSF process was carried out at the optimum temperature of hydrolysis and fermentation. [ Result] In SHF process, the efficiency of ethanol production was similar during both supematant and mixture fermentation, and yeast was more active during the mixture fermentation. In SSF process, the efficiency of ethanol production was higher at 35 ℃, and the production of xylose was higher than that in hydrolysis process. [ Conclusion] Under the experimental conditions, the efficiency of ethanol production during simultaneous saccharification and fermentation was higher than that during separate hydrolysis and fermentation.

Monitoring Saccharification Process in Brewery Industry Using Quality Control Charts

The aim of this study was to establish a control system for saccharification process using quality control charts. To achieve this goal, temperature, pH and brix were measured at 12 minutes intervals for 15 consecutive batches which took 2 hours each. The time variations for three process parameters were assessed to establish a good understanding of the saccharification process. The temperature varied between 58℃ and 62℃ while the pH decreased slowly due to oxidation, values of which varied between 5.7 and 5.0. Brix values increased linearly with time. The initial and final values of the three parameters varied from one batch to another. Of the three parameters, brix was not well represented on the quality control charts due to wide difference between initial and final values during saccharification. The final brix values varied between batches, from 10.6% to 11.6%. The control charts used in this study were X-bar and Range charts. The rules for interpreting control charts were implemented for both X-bar and R charts, results of which showed that the process was out of control, although some rules were not violated due to little number of batches studied. The values of for temperature and pH data (2.27℃ and 0.35, respectively) were lower compared to brix data (11.2%). The corresponding values of span between control limits, SPx and SPR for temperature and pH were also comparatively lower than those established from brix data. Due to larger values of for brix measurements, the corresponding control charts for brix were insensitive in identifying out-of-control points during saccharification process.

Cellulosomal hemicellulases:Indispensable players for ensuring effective lignocellulose bioconversion

The bioconversion of lignocellulose has attracted global attention,due to the significant potential of agricultural and forestry wastes as renewable zero-carbon resources and the urgent need for substituting fossil carbon.The cellulosome system is a multi-enzyme complex produced by anaerobic bacteria,which comprises cellulases,hemicellulases,and associated enzymatic and non-enzymatic components that promote biomass conversion.To enhance their efficiency in degrading recalcitrant lignocellulosic matrices,cellulosomes have been employed to construct biocatalysts for lignocellulose bioconversion,such as consolidated bioprocessing and consolidated bio-saccharification.Hemicelluloses,the second most abundant polysaccharides in plant cell walls,hold valuable application potential but can also induce inhibitory effects on cellulose hydrolysis,thus highlighting the indispensable roles of hemicellulases within the cellulosome complex.This review evaluated current research on cellulosomal hemicellulases,comparing their types,abundance,and regulation,primarily focusing on eight known cellulosome-producing species of different origins.We also reviewed their growth conditions,their hemicellulose-degrading capabilities,and the inhibitory effects of hemicellulose on cellulosome-based lignocellulose saccharification.Finally,we proposed strategies for targeted enhancement of hemicellulase in cellulosomes to improve lignocellulose bioconversion in future studies.

Loosening Xyloglucan Accelerates the Enzymatic Degradation of Cellulose in Wood

In order to create trees in which cellulose, the most abundant component in biomass, can be enzymatically hydrolyzed highly for the production of bioethanol, we examined the saccharification of xylem from several transgenic poplars, each overexpressing either xyloglucanase, cellulase, xylanase, or galactanase. The level of cellulose degradation achieved by a cellulase preparation was markedly greater in the xylem overexpressing xyloglucanase and much greater in the xylems overexpressing xylanase and cellulase than in the xylem of the wild-type plant. Although a high degree of degradation occurred in all xylems at all loci, the crystalline region of the cellulose microfibrUs was highly degraded in the xylem overexpressing xyloglucanase. Since the complex between microfibrils and xyloglucans could be one region that is particularly resistant to cellulose degradation, loosening xyloglucan could facilitate the enzymatic hydrolysis of cellulose in wood.

Oligomer saccharide reduction during dilute acid pretreatment co-catalyzed with Lewis acids on corn stover biomass

The dilute sulfuric acid pretreatment of lignocellulosic biomass is a well understood process that significantly enhances the yield of glucose after enzymatic saccharification.The goal of this research was to perform a systematic study to evaluate the yield of fermentable sugars during dilute sulfuric acid pretreatment that is co-catalyzed with the transition metal Lewis acid salts:AlCl_(3),FeCl_(2),FeCl_(3),and La(OTf)_(3).All Lewis acids apart from FeCl_(2)reduced the presence of xylo-oligomers by a large margin when compared to the non-co-catalyzed control sample pretreatments.The presence of these xylo-oligomers acts as inhibitors during enzymatic saccaharification step.The Lewis acids AlCl_(3),FeCl_(3),and La(OTf)_(3)were also able to marginally increase the overall enzymatic digestibility specifically for corn stover pretreated at 160℃with 10 mM of Lewis acids.The hard Lewis acid such as AlCl3 increased the formation inhibitory products such as furfural and 5-hydroxymethylfurfural(HMF).There was good correlation between reduction of xylo-oligomers and increased concentration furfural with increase in Lewis acid hardness.

Aqua-ammonia pretreatment of corn stover for enhancing enzymatic saccharification

Aqua-ammonia pretreatment of corn stover was provided in a 1.2 L high pressure reactor with two ammonia:biomass ratios of 1:1(w/w)and 2:1(w/w);at three temperatures:60℃,90℃and 120℃,and two treatment time:5 min and 30 min.Pretreatment with water was used as control.The pretreated samples were saccharified to fermentable sugars by commercial enzymes ACCELERASE 1500(cellulase)and ACCELERASE XC(xylanases).For ammonia:biomass ratio of 1:1,the yield of total fermentable sugar was 87%at 90℃for 30 min treatment.In case of ammonia:biomass ratio of 2:1,fermentable sugar yield increased four fold of that of control.Maximum fermentable sugar yield of 99%was obtained for 2:1 ammonia:biomass ratio,90℃,and 30 min treatment time.The results of this study are very promising for improving fermentable sugar yield from corn stover using smaller amount of ammonia than the ammonia fiber explosion and other pretreatments such as strong acid or alkali pretreatments.However,further optimization is required for reducing pretreatment time.