甜高粱茎秆汁液制取酒精的试验研究

生物酒精越来越受到世界各国的广泛重视,在众多的生物酒精原料中,甜高粱是很有发展前途的一种.本试验以甜高粱茎秆汁液为发酵原料,采用近年来正在研究和开发的固定化酵母技术,并结合国内外试验正采用的添加豆饼粉工艺,在流化床生物反应器上进行了试验研究.     

Fuel ethanol production from sweet sorghum bagasse using microwave irradiation

Sweet sorghum is a hardy crop that can be grown on marginal land and can provide both food and energy in an integrated food and energy system. Lignocellulose rich sweet sorghum bagasse (solid left over after starch and juice extraction) can be converted to bioethanol using a variety of technologies. The largest barrier to commercial production of fuel ethanol from lignocellulosic material remains the high processing costs associated with enzymatic hydrolysis and the use of acids and bases in the pretreatment step. In this paper, sweet sorghum bagasse was pretreated and hydrolysed in a single step using microwave irradiation. A total sugar yield of 820 g kg⁻¹ was obtained in a 50 g kg⁻¹ sulphuric acid solution in water, with a power input of 43.2 kJ g⁻¹ of dry biomass (i.e. 20 min at 180 W power setting). An ethanol yield based on total sugar of 480 g kg⁻¹ was obtained after 24 h of fermentation using a mixed culture of organisms. These results show the potential for producing as much as 0.252 m³ tonne⁻¹ or 33 m³ ha⁻¹ ethanol using only the lignocellulose part of the stalks, which is high enough to make the process economically attractive.     

Optimization of ethanol production from sweet sorghum (Sorghum bicolor) juice using response surface methodology

Sweet sorghum juice was fermented into ethanol using Saccharomyces cerevisiae (ATCC 24858). Factorial experimental design, regression analysis and response surface method were used to analyze the effects of the process parameters including juice solid concentration from 6.5 to 26% (by mass), yeast load from 0.5 g L⁻¹ to 2 g L⁻¹ and fermentation temperature from 30 °C to 40 °C on the ethanol yield, final ethanol concentration and fermentation kinetics. The fermentation temperature, which had no significant effect on the ethanol yield and final ethanol concentration, could be set at 35 °C to achieve the maximum fermentation rate. The yeast load, which had no significant effect on the final ethanol concentration and fermentation rate, could be set at 1 g L⁻¹ to achieve the maximum ethanol yield. The juice solid concentration had significant inverse effects on the ethanol yield and final ethanol concentration but a slight effect on the fermentation rate. The raw juice at a solid concentration of 13% (by mass) could be directly used during fermentation. At the fermentation temperature of 35 °C, yeast solid concentration of 1 g L⁻¹ and juice solid concentration of 13%, the predicted ethanol yield was 101.1% and the predicted final ethanol concentration was 49.48 g L⁻¹ after 72 h fermentation. Under this fermentation condition, the modified Gompertz's equation could be used to predict the fermentation kinetics. The predicted maximum ethanol generation rate was 2.37 g L⁻¹ h⁻¹.     

Study on genotypic variation for ethanol production from sweet sorghum juice

Sugarcane molasses is the main source for ethanol production in India. Sweet sorghum with its juicy stem containing sugars equivalent to that of sugarcane is a very good alternative for bio-ethanol production to meet the energy needs of the country. Sweet sorghum is drought resistant, water logging resistant and saline–alkaline tolerant. Growing sweet sorghum for ethanol production is relatively easy and economical and ethanol produced from sweet sorghum is eco-friendly. In view of this, it is important to identify superior genotypes for ethanol production in terms of percent juice brix, juice extractability, total fermentable sugars, ethanol yield and fermentation efficiency. This paper presents the study on the variability observed for the production of ethanol by various sweet sorghum genotypes in a laboratory fermentor. Five Sweet Sorghum (Sorghum bicolor L. Moench) genotypes were evaluated for ethanol production from stalk juice (Keller, SSV 84, Wray, NSSH 104 and BJ 248). Sweet sorghum juice differs from cane juice mainly in its higher content of starch and aconitic acid. Data were collected for biomass yield; stalk sugar yield and ethanol production in five genotypes. Maximum ethanol production of 9.0%w/v ethanol was obtained with Keller variety (20% sugar concentration was used), and decreased for other genotypes. A distiller's strain of Saccharomyces cerevisiae (gifted by Seagram Distilleries Ltd.) was employed for fermentation. The fermentation efficiency (FE) was 94.7% for this strain. High biomass of yeast was obtained with BJ 248 variety. When the similar experiments were conducted with unsterile sweet sorghum juice (15% sugar concentration) 6.47%w/v ethanol was produced.     

Optimization of media conditions for the production of ethanol from sweet sorghum juice by immobilized Saccharomyces cerevisiae

In order to obtain high ethanol yield and fermentation rate, response surface methodology (RSM) was employed to study the effect of culture medium on the ethanol productivity from stalk juice of sweet sorghum by immobilized yeast. A 2³ central composite design (CCD) was chosen to explain the combined effects of the medium constituents, viz. nitrogen (adjusted by adding (NH₄)₂SO₄), phosphorus (adjusted by adding KH₂PO₄), and pH. A mathematical correlation about the influence of the nitrogen, phosphorus, and pH on the ethanol productivity was established. It predicted that the maximum ethanol production rate (119.12 g/l h) was observed for a medium consisting of 0.77 g/l phosphorus, 2.15 g/l nitrogen, and pH = 6.39. Under this condition, the ethanol fermentation rate was 122.85 g/l h.     

Optimization of biohydrogen production from sweet sorghum syrup using statistical methods

This study employed statistically based experimental designs to optimize fermentation conditions for hydrogen production from sweet sorghum syrup by anaerobic mixed cultures. Initial screening of important factors influencing hydrogen production, i.e., total sugar, initial pH, nutrient solution, iron (II) sulphate (FeSO₄), peptone and sodium bicarbonate was conducted by the Plackett–Burman method. Results indicated that only FeSO₄ had statistically significant (P ≤ 0.005) influences on specific hydrogen production (P_s) while total sugar and initial pH had an interdependent effect on P_s. Optimal conditions for the maximal P_s were 25 g/L total sugar, 4.75 initial pH and 1.45 g/L FeSO₄ in which P_s of 6897 mL H₂/L was estimated. Estimated optimum conditions revealed only 0.04% difference from the actual P_s of 6864 mL H₂/L which suggested that the optimal conditions obtained can be practically applied to produce hydrogen from sweet sorghum syrup with the least error.     

Lipid production from sweet sorghum bagasse through yeast fermentation

Cryptococcus curvatus has great potential in fermenting unconditioned hydrolysates of sweet sorghum bagasse. With hydrolysates obtained by enzymatic hydrolysis of the solid pretreated by microwave with lime, the maximal yeast cell dry weight and lipid content were 10.83 g/l and 73.26%, respectively. For hydrolysates obtained in the same way but without lime, these two parameters were 15.50 g/l and 63.98%, respectively. During yeast fermentation, glucose and xylose were consumed simultaneously while cellobiose was released from the residual bagasse. The presence of lime, on one hand, made cellulose more accessible to enzymes as evidenced by higher total reducing sugar release compared to that without during enzymatic hydrolysis step; on the other hand, it caused the degradation of sugars to non-sugar chemicals during pretreatment step. As a result, higher lipid yield of 0.11 g/g bagasse or 0.65 ton/hectare of land was achieved from the pathway of microwave pretreatment and enzymatic hydrolysis while 0.09 g/g bagasse or 0.51 ton/hectare of land was attained from the process of lime-assisted microwave pretreatment followed by the same enzymatic saccharification.     

Enhanced hydrogen and volatile fatty acid production from sweet sorghum stalks by two-steps dark fermentation with dilute acid treatment in between

This study investigated the potential of hydrogen and volatile fatty acid coproduction from two steps dark fermentation with dilute acid treatments of the residual slurry after 1st step fermentation. Sweet sorghum stalks (SS) was used as substrate along with Clostridium thermosaccharolyticum as production microbe. Residual lignocelluloses after 1st step fermentation were treated for 1 h by sulfuric acid concentration of 0.25, 0.5, 1.0, 1.5, 2.0 and 2.5% (w/v) with different reaction temperature of 120, 90 and 60 °C were studied. The optimum severity conditions for the highest yield of products found from the treatment acid concentration of 1.5% (w/v) at 120 °C for 10 g/L of substrate concentration. Experimental data showed that two-step fermentation increased 76% hydrogen, 84% acetic acid and 113% of butyric acid production from single step. Maximum yields of hydrogen, acetic acid and butyric acid were 5.77 mmol/g-substrate, 2.17 g/L and 2.07 g/L respectively. This two-step fermentation for hydrogen and VFA production using the whole slurry would be a promising approach to SS biorefinery.     

甜高粱的适生区及能源资源潜力研究

运用中国资源环境数据库中的1km DEM数据、1:100万中国土地利用数据、省区面元数据和中国自然地图数据库中的年降水量、活动积温和土壤pH值数据,在研究现有甜高粱生长的限制性环境因子的基础上,确定了甜高粱生长发育的环境因子及其阈限值,形成了年降水量≥400mm、活动积温2500～4500℃、土壤pH值6.0～8.5、坡度≤15°甜高粱在某地区能够生长发育的4个阈限指标;假定甜高粱种植不占用耕地、林地和草地,不占用沼泽地等生态用地,基于GIS空间分析功能,计算出甜高粱适宜种植的边际性土地资源的空间分布、类型及面积。研究认为,中国适宜于甜高粱种植的边际性土地资源有440.7万hm~2,单位面积甜高粱乙醇产量按3.9t/hm~2计算,在适宜区种植甜高粱可提炼出1718.7万t燃料乙醇,相当于2006年全国汽油消费量的32.8%。     

Fuel ethanol production from steam-pretreated corn stover using SSF at higher dry matter content

Replacing fossil fuels by bio-fuels has many advantages, such as the reduction of CO₂-emission to the atmosphere, the possibility for non-oil-producing countries to be self-sufficient in fuel, and increased local job opportunities. Bio-ethanol is such a promising renewable fuel. However, today it is produced from sugar or starch—raw materials that are relatively expensive. To lower the production cost of bio-ethanol the cost of the raw material must be reduced and the production process made more efficient. The production of bio-ethanol from corn stover using simultaneous saccharification and fermentation (SSF) at high dry matter content addresses both issues. Corn stover is an agricultural by-product and thus has a low economic value. SSF at high dry matter content results in a high ethanol concentration in the fermented slurry, thereby decreasing the energy demand in the subsequent distillation step.In this study, SSF was performed on steam-pretreated corn stover at 5, 7.5 and 10% water-insoluble solids (WIS) with 2 g/L hexose-fermenting Saccharomyces cerevisiae (ordinary compressed baker's yeast). SSF at 10% WIS resulted in an ethanol yield of 74% based on the glucose content in the raw material and an ethanol concentration of 25 g/L. Neither higher yeast concentration (5 g/L) nor yeast cultivated on the liquid after the pretreatment resulted, under these conditions, in a higher overall ethanol yield.     

The productive potentials of sweet sorghum ethanol in China

As one of the important non-grain energy crops, sweet sorghum has attracted the attention of scientific community and decision makers of the world since decades. But insufficient study has been done about the spatial suitability distribution and ethanol potential of sweet sorghum in China. This paper attempts to probe into the spatial distribution and ethanol potential of sweet sorghum in China by ArcGIS methods. Data used for the analysis include the spatial data of climate, soil, topography and land use, and literatures relevant for sweet sorghum studies. The results show that although sweet sorghum can be planted in the majority of lands in China, the suitable unused lands for large-scale planting (unit area not less than 100 hm²) are only as much as 78.6 × 10⁴ hm²; and the productive potentials of ethanol from these lands are 157.1 × 10⁴–294.6 × 10⁴ t/year, which can only meet 24.8–46.4% of current demand for E10 (gasoline mixed with 10% ethanol) in China (assumption of the energy efficiency of E10 is equivalent to that of pure petroleum). If all the common grain sorghum at present were replaced by sweet sorghum, the average ethanol yield of 244.0 × 10⁴ t/year can be added, and thus the productive potentials of sweet sorghum ethanol can satisfy 63.2–84.9% of current demand for E10 of China. In general, Heilongjiang, Jilin, Inner Mongolia and Liaoning rank the highest in productive potentials of sweet sorghum ethanol, followed by Hebei, Shanxi, Sichuan, and some other provinces. It is suggested that these regions should be regarded as the priority development zones for sweet sorghum ethanol in China.     

Screening and optimization of trace elements supplement in sweet sorghum juice for ethanol production

Eight trace elements were screened for increasing efficiency of ethanol yield from sweet sorghum juice using the Plackett-Burman design method. MnCl₂·4H₂O, CoCl₂·6H₂O and biotin was screened as the significant variables which have positive effects on ethanol production from sweet sorghum juice. The values of MnCl₂·4H₂O, CoCl₂·6H₂O and biotin, optimized by Box-Behnken design method, were 7.70 mg L⁻¹, 15.74 mg L⁻¹ and 11.97 mg L⁻¹, respectively. The experimental efficiency of ethanol yield under optimal conditions was 89.30 ± 0.10%, which enhances the efficiency of ethanol yield by 5.63% by the addition of MnCl₂·4H₂O, CoCl₂·6H₂O and biotin. The results from this study have identified optimal conditions as a foundation for pilot scale ethanol production.     

Optimization and analysis of a bioethanol agro-industrial system from sweet sorghum

The use of non-food crops for bioethanol production represents an important trend for renewable energy in China. In this paper, a bioethanol agro-industrial system with distributed fermentation plants from sweet sorghum is presented. The system consists of the following processes: sweet sorghum cultivation, crude ethanol production, ethanol refining and by-product utilization. The plant capacities of crude ethanol and pure ethanol, in different fractions of useful land, are optimized. Assuming a minimum cost of investment, transport, operation and so on, the optimum capacity of the pure ethanol factory is 50,000 tonnes/year. Moreover, this bioethanol system, which requires ca. 13,300 ha (hectares) of non-cultivated land to supply the raw materials, can provide 26,000 jobs for rural workers. The income from the sale of the crops is approximately 71 million RMB Yuan and the ethanol production income is approximately 94 million RMB Yuan. The potential savings in CO₂ emissions are ca. 423,000 tonnes/year and clear economic, social and environmental benefits can be realized.     

Influence of pH on fermentative hydrogen production from sweet sorghum extract

The present study focused on the influence of pH on the fermentative hydrogen production from the sugars of sweet sorghum extract, in a continuous stirred tank bioreactor. The reactor was operated at a Hydraulic Retention Time of 12 h and a pH range of 3.5–6.5. The maximum hydrogen production rate and yield were obtained at pH 5.3 and were 1752 ± 54 mL H₂/d or 3.50 ± 0.07 L H₂/L reactor/d and 0.93 ± 0.03 mol H₂/mol glucose consumed or 10.51 L H₂/kg sweet sorghum, respectively. The main metabolic product at this pH value was butyric acid. The hydrogen productivity and yield were still at high levels for the pH range of 5.3–4.7, suggesting a pH value of 4.7 as optimum for hydrogen production from an economical point of view, since the energy demand for chemicals is lower at this pH. At this pH range, the dominant fermentation product was butyric acid but when the pH culture sharply decreased to 3.5, hydrogen evolution ceased and the dominant metabolic products were lactic acid and ethanol.     

油污地甜高粱茎秆汁液制取酒精的试验研究

采用正交试验的方法,以辽宁沈抚污灌区栽种的甜高粱茎秆为试材,研究了氮、钾、镁营养盐填加量对酒精产率的影响,确定了甜高梁发酵酒精的适宜工艺。结果表明,在油污地栽种的甜高粱可用来发酵生产酒精;在发酵液中添加0．5％的磷酸二氧钾,0．05％的硫酸铵,0．05％的硫酸镁,5-6h后可得到较高的酒精产率（可达理论产率的93％）。     

甜高粱秸秆燃料乙醇产业化问题与对策的探讨

甜高粱具有极高的光合速率,有"高能植物"之称,其单位种植面积的乙醇产量较高.甜高粱特别适合在我国栽培,甜高粱燃料乙醇极具开发价值,它对能源安全和环境保护具有举足轻重的作用.文章简单介绍了新疆甜高粱用于生产低成本燃料乙醇的优势、试验情况以及产业化过程中面临的问题,并提出了解决这些问题应采取的对策.     

Effect of substrate concentration on fermentative hydrogen production from sweet sorghum extract

The aim of the present study was to assess the influence of substrate concentration on the fermentative hydrogen production from sweet sorghum extract, in a continuous stirred tank bioreactor. The reactor was operated at a Hydraulic Retention Time (HRT) of 12 h and carbohydrate concentrations ranging from 9.89 to 20.99 g/L, in glucose equivalents. The maximum hydrogen production rate and yield were obtained at the concentration of 17.50 g carbohydrates/L and were 2.93 ± 0.09 L H₂/L reactor/d and 0.74 ± 0.02 mol H₂/mol glucose consumed, corresponding to 8.81 ± 0.02 L H₂/kg sweet sorghum, respectively. The main metabolic product at all steady states was butyric acid, while ethanol production was high at high substrate concentrations. The experiments showed that hydrogen productivity depends significantly on the initial carbohydrate concentration, which also influences the distribution of the metabolic products.     

Modeling of fermentative hydrogen production from sweet sorghum extract based on modified ADM1

The Anaerobic digestion model 1 (ADM1) framework can be used to predict fermentative hydrogen production, since the latter is directly related to the acidogenic stage of the anaerobic digestion process. In this study, the ADM1 model framework was used to simulate and predict the process of fermentative hydrogen production from the extractable sugars of sweet sorghum biomass. Kinetic parameters for sugars’ consumption and yield coefficients of acetic, propionic and butyric acid production were estimated using the experimental data obtained from the steady states of a CSTR. Batch experiments were used for kinetic parameter validation. Since the ADM1 does not account for metabolic products such as lactic acid and ethanol that are crucial during the fermentative hydrogen production process, the structure of the model was modified to include lactate and ethanol among the metabolites and to improve the predictions. The modified ADM1 simulated satisfactorily batch experiments although further modifications could be made in order to further improve the predictions for the hydrogenogenic process.     

Optimization of very high gravity fermentation process for ethanol production from industrial sugar beet syrup

In order to reduce production costs and environmental impact of bioethanol from sugar beet low purity syrup 2, an intensification of the industrial alcoholic fermentation carried out by Saccharomyces cerevisiae is necessary. Two fermentation processes were tested: multi-stage batch and fed-batch fermentations with different operating conditions. It was established that the fed-batch process was the most efficient to reach the highest ethanol concentration. This process allowed to minimize both growth and ethanol production inhibitions by high sugar concentrations or ethanol. Thus, a good management of the operating conditions (initial volume and feeding rate) could produce 15.2% (v/v) ethanol in 53 h without residual sucrose and with an ethanol productivity of 2.3 g L h⁻¹.     

Sweet sorghum as a whole-crop feedstock for ethanol production

The potential of sweet sorghum as an alternative crop for ethanol production was investigated in this study. Initially, the enzymatic hydrolysis of sorghum grains was optimized, and the hydrolysate produced under optimal conditions was used for ethanol production with an industrial strain of Saccharomyces cerevisiae, resulting in an ethanol concentration of 87 g L⁻¹. From the sugary fraction (sweet sorghum juice), 72 g L⁻¹ ethanol was produced. The sweet sorghum bagasse was submitted to acid pretreatment for hemicellulose removal and hydrolysis, and a flocculant strain of Scheffersomyces stipitis was used to evaluate the fermentability of the hemicellulosic hydrolysate. This process yielded an ethanol concentration of 30 g L⁻¹ at 23 h of fermentation. After acid pretreatment, the remaining solid underwent an alkaline extraction for lignin removal. This partially delignified material, known as partially delignified lignin (PDC), was enriched with nutrients in a solid/liquid ratio of 1 g/3.33 mL and subjected to simultaneous saccharification and fermentation (SSF) process, resulting in an ethanol concentration of 85 g L⁻¹ at 21 h of fermentation. Thus, from the conversion of starchy, sugary and lignocellulosic fractions approximately 160 L ethanol.ton⁻¹ sweet sorghum was obtained. This amount corresponds to 13,600 L ethanol.ha⁻¹.