秸秆的强化糖化技术及其生物制氢的实验研究

通过对植物秸秆的糖化降解,在不同时间、不同温度下测定糖含量,并进行产氢实验.结果表明,用盐酸降解植物秸秆的效果比醋酸好,在时间为1h、温度在20℃时,各有最大的糖度值36.8、35.4Bdx,相对应产氢量为0.02mL、0.0182mL H2/L糖化液.因此,利用秸秆糖化技术并进行产氢的可行性研究会成为一个研究热点.     

玉米秸秆同步糖化共发酵工艺条件优化

以经过生物预处理后的玉米秸秆为原料,采用混合菌进行同步糖化发酵。以分光光度法测定发酵液中的乙醇含量,对发酵时间、发酵温度、接种比例、纤维素酶用量4个条件进行单因素试验分析,再通过正交试验对发酵条件进行优化。试验结果表明,最适发酵条件:发酵温度为36℃,发酵时间为96 h,接种比例为1∶1,纤维素酶用量为40 IU/g,乙醇产率为12.03%。     

玉米秸秆厌氧发酵生物制氢放大试验研究

在前期试验的基础上,以牛粪堆肥作为菌种来源,以玉米秸秆作为发酵底物,分别在5 L和30 L反应器中进行厌氧发酵制氢试验.试验结果表明:30L反应器处理底物的能力为15 g/L,5 L反应器为10g/L,其相应的底物最高产氢潜力分别为198.25,109.58 ml/g.5 L反应器和30 L反应器的最佳搅拌速率分别为120,100r/min,累积产氢量分别为5.51,58.50L.发酵过程中微生物的生长符合典型的微生物生长规律.5 L反应器和30 L反应器的气相产物中最高含氢量分别为55%和61%.由液相发酵产物确定两反应器中的发酵均为丁酸型发酵.修正后的Gompezrt产氢动力学模型能够很好地描述两反应器的发酵产氢过程,反应器经过放大后,其产氢性能得到了明显的提高.     

玉米秸秆预处理对厌氧发酵制氢影响的研究

为提高玉米秸秆的产氢能力,实验研究了蒸汽爆破预处理、硫酸预处理、氢氧化钠预处理、盐酸预处理和酸化(碱化)气爆预处理5种预处理方法对玉米秸秆发酵产氢能力的影响。结果表明,预处理可以将秸秆中相当一部分纤维素和半纤维素水解生成还原糖,其中质量分数为0.8%的H2SO4酸化汽爆预处理对秸秆的水解效果最好。在固-液比1∶10、H2SO4质量分数0.8%、保持微沸状态30min的处理条件下,秸秆的糖含量达到最大值24.57%,最大氢气产量为141mL/g。     

氨基酸对光合菌群HAU-M1发酵玉米秸秆产氢能力的影响

为研究氨基酸对光合发酵产氢的影响,以玉米秸秆为产氢底物,以比产氢量为主要指标,分别添加不同浓度的L-半胱氨酸和L-苏氨酸,并对其累积产氢量、pH值、氧化还原电位(ORP)和产氢动力学结果进行分析.结果表明:L-半胱氨酸最佳浓度为0.6 g/L,此时比产氢量为(54.4±0.75)mL/g,比对照组提高45.45％;L-...     

生物制氢技术发展历程及其特征

介绍了生物制氢技术的发展历程,通过分析各种生物制氢技术的特征及研究进展,指出光合生物制氢技术是一种最具发展潜力的生物制氢方法。     

猪粪污水浓度对球形红假单胞菌光合制氢的影响

通过猪粪污水光合制氢技术的实验,重点研究了畜禽粪便污水原料浓度对利用红假单胞菌(RHODOBACTERSPHAEROIDES)1.1737菌株进行光合产氢的影响规律,结果表明光合产氢量与原料浓度成正比,当畜禽粪便污水中的COD含量为5687MG/L时的体积产氢率可达23.7ML/(L.D),则单位COD体积产氢率达11.3ML/(G.D),将光合生物制氢和畜禽粪便污水处理有机地结合起来,具有显著的社会、环境和经济效益,为畜禽粪便资源化技术研究开发提供科学参考。     

紫花苜蓿酶解光合生物制氢工艺正交优化实验

为了研究紫花苜蓿酶解液作为光合制氢原料时的最佳产氢工艺条件,对产氢影响较为显著的温度、光照强度、初始pH值三种因素设计了三因素三水平L9(33)正交实验,并对实验结果进行直观分析与方差分析,以获取最佳产氢工艺条件。实验结果表明:在所选水平范围内,各因素对能源草产氢的影响主次顺序为温度→光照强度→初始pH值;由方差分析可知,温度和光照强度对能源草光合产氢性能影响为显著;初始pH值为不显著;由各因素水平值的均值可见,能源草光合生物制氢的最佳工艺水平为30℃、pH=7、光照度为3 000 lx。     

楸叶泡桐叶光合生物产氢实验研究

以楸叶泡桐叶为底物,累积产氢量和产氢速率为主要考察目标,研究不同底物质量浓度对光合细菌HAU-M1同步糖化发酵产氢的影响,并对发酵过程中发酵液的pH值和还原糖浓度变化进行分析.实验结果表明:当底物浓度为25 g/L时,产氢效果最好,得到最大累积产氢量167.85 mL,氢气浓度达到39.5％;产氢高峰期集中在24～60...     

磷酸盐浓度对产氢细菌Ethanoligenens harbinense YUAN-3生长和产气的影响

以产氧发酵细菌YUAN-3(Ethanoligenens harbinense)为研究对象,通过间歇产氢实验,考察磷酸盐的浓度对YUAN-3生长和产气的影响.研究结果表明在磷酸盐浓度小于15mmol/L时,生物量较高,细胞干重大于0.4g/L;整个发酵过程的平均产氢速率和比产氢率在磷酸盐浓度为8mmol/L时达到最大,为5.92mmol/g-干细胞·h和2.86molH2/mol-葡萄糖.     

Biological hydrogen production from steam-exploded straw by simultaneous saccharification and fermentation

Hydrogen was produced by simultaneous saccharification and fermentation from steam-exploded corn straw (SECS) using Clostridium butyricum AS1.209. Effect of various process parameters, such as solid to liquid ratio, enzyme loading and initial pH, etc., were examined with respect to maximum hydrogen productivity which was obtained by fitting the cumulative hydrogen production data to a modified Gompertz equation. Maximum specific hydrogen production rate and maximal hydrogen yield were 126 ml/g VSS d and 68 ml/g SECS, respectively. The yield of soluble metabolites was 197.7 mg/g SECS. Acetic acid accounted for 46% of the total was the most abundant product and this shows that hydrogen production from SECS was essentially acetate-type fermentation. Hydrogen production by simultaneous saccharification and fermentation of SECS has the predominance of short lag-stage and high maximum specific hydrogen production rate and it was a promising method for hydrogen production and straw biomass conversion.     

Evaluation of fuel ethanol production from aqueous ammonia-treated rice straw via simultaneous saccharification and fermentation

Rice straw (RS) has been considered a promising feedstock for ethanol production in Asia. However, the recalcitrance of biomass, particularly the presence of lignin, hinders the enzymatic saccharification of polysaccharides in RS and consequently decreases the ethanol yield. Here, we used aqueous ammonia pretreatment to remove lignin from RS (aRS). The reaction conditions were a solid:liquid ratio of 1:12, an ammonia concentration of 27% (w w⁻¹), room temperature, and a 2-week incubation. We evaluated enzymatic digestibility and the ethanol production yield. A 42% reduction in lignin content increased the glucan conversion of aRS to glucose from 20 to 71% using a combination of Cellic Ctec2 cellulases and Cellic Htec2 xylanases at enzyme loads of 15 FPU +100 XU g⁻¹ solid. Scanning electron microscopy highlighted the extensive removal of external fibres and increased porosity of aRS, which aided the accessibility of cellulose for enzymes. Using the same enzyme dosage and a solid load of 100 g L⁻¹, simultaneous saccharification and fermentation using a monoculture of Saccharomyces cerevisiae and co-culture with Candida tropicalis yielded ethanol concentrations of 22 and 25 g L⁻¹, corresponding to fermentation efficiencies of 96 and 86% fermentation, respectively. The volumetric ethanol productivities for these systems were 0.45 and 0.52 g L⁻¹ h⁻¹. However, the ethanol yield based on the theoretical glucose and xylose concentrations was lower for the co-culture (0.44 g g⁻¹) than the monoculture (0.49 g g⁻¹) due to the low xylose consumption. Further research should optimise fermentation variables or select/improve microbial strains capable of fermenting xylose to increase the overall ethanol production yield.     

Bioethanol production from pretreated Miscanthus floridulus biomass by simultaneous saccharification and fermentation

The production of ethanol from the fast-growing perennial C4 grass Miscanthus floridulus by simultaneous saccharification and fermentation (SSF) was investigated. M. floridulus biomass was composed of 36.3% glucan, 22.8% hemicellulose, and 21.3% lignin (based on dried mass). Prior to SSF, harvested stems of M. floridulus were pretreated separately by alkali treatment at room temperature, alkali treatment at 90 °C, steam explosion, and acid-catalyzed steam explosion. The delignification rates were determined to be 73.7%, 61.5%, 42.7%, and 63.5%, respectively, by these four methods, and the hemicellulose removal rates were 51.5%, 85.1%, 70.5%, and 97.3%, respectively. SSF of residual solids after various pretreatments was performed with dried yeast (Saccharomyces cerevisiae) and cellulases (Accellerase 1000) by using 10% water-insoluble solids (WIS) of the pretreated M. floridulus as the substrate. The ethanol yields from 72-h SSF of M. floridulus biomass after these pretreatments were 48.9 ± 3.5, 78.4 ± 1.0, 46.4 ± 0.1, and 69.0 ± 0.1% (w/w), respectively, while the ethanol concentrations after 72-h SSF were determined to be 15.4 ± 1.1, 27.5 ± 0.3, 13.9 ± 0.1, and 30.8 ± 0.1 g/L, respectively. Overall, the highest amount of ethanol (0.124 g/g-dried raw material) was generated from dried raw material of M. floridulus after alkaline pretreatment at 90 °C. The acid-catalyzed steam explosion pretreatment also resulted in a high ethanol yield (0.122 g/g-dried raw material). Pretreatment resulting in high lignin and hemicellulose removal rates could make biomass more accessible to enzyme hydrolysis and lead to higher ethanol production.     

木糖厌氧发酵产氢特性研究

以木糖作为厌氧发酵产氢底物,热预处理(100℃,处理20 min)的厌氧颗粒污泥作为接种物,研究了中温条件(37℃)下厌氧发酵产氢特性.结果表明,当反应进行至50 h时,累积产氢量最大,为81.11 mL;乙酸、丁酸和乙醇是液相末端产物中的主要物质,其中乙酸和丁酸的浓度分别为1290 mg/L和1225 mg/L,发酵类型是典型的丁酸型发酵;反应体系的pH值开始降低,最后稳定在4.40左右,形成一个稳定的缓冲体系.     

Photo-fermentative hydrogen production from mixed substrate by mixed bacteria

Photo-fermentative H₂ production by mixed bacteria and pure bacterium Rhodopseudomonas faecalis RLD-53 using single and mixed substrate as carbon source was investigated in batch culture. Experimental results showed that 60 mmol/L acetate was the optimal concentration for mixed bacterial H₂ production and maximum cumulative H₂ volume was 2468 ± 123 mL H₂/L-culture. It was also found that propionate or butyrate was a key factor for enhancing H₂ production in mixed substrate system. Photo-H₂ production can be greatly promoted when proper concentration of propionate and butyrate were added into acetate medium as mixed substrate and a higher H₂ yield of 2931 ± 146 mL H₂/L-culture was obtained. In addition, it was worth noting that when the strain RLD-53 was added into mixed bacteria with different concentration ratios, H₂ yield did not yet increase. Interestingly, H₂ production capacity gradually decreased with ratio of strain RLD-53 to mixed bacteria from 8:0 to 4:4, and then gradually increased from 4:4 to 0:8. This implied that the competition relationship between strain RLD-53 and mixed bacteria in substrate utilization strongly influenced their H₂ production.     

Effects of pH value and substrate concentration on hydrogen production from the anaerobic fermentation of glucose

A series of batch experiments were conducted to investigate the effects of pH and glucose concentrations on biological hydrogen production by using the natural sludge obtained from the bed of a local river as inoculant. Batch experiments numbered series I and II were designed at an initial and constant pH of 5.0–7.0 with 1.0 increment and four different glucose concentrations (5.0, 7.5, 10 and 20 g glucose/L). The results showed that the optimal condition for anaerobic fermentative hydrogen production is 7.5 g glucose/L and constant pH 6.0 with a maximum H₂ production rate of 0.22 mol H₂ mol⁻¹ glucose h⁻¹, a cumulative H₂ yield of 1.83 mol H₂ mol⁻¹ glucose and a H₂ percentage of 63 in biogas.     

Influence of initial anolyte pH and temperature on hydrogen production through simultaneous saccharification and fermentation of lignocellulose in microbial electrolysis cell

An investigation on the performance of hydrogen production by simultaneous saccharification and fermentation (SSF) in a dual-chamber microbial electrolysis cell (MEC) was carried out to consider different anolyte pH levels and culture temperatures, and the influences of anolyte pH value and culture temperature on changes of current, organic acid and pH value were also evaluated. The maximal hydrogen production rate (HPR) of 2.46 mmol/L/D (hydrogen energy recovery 219.02%) was obtained at the initial anolyte pH of 6.5. Within the range of the tested operation temperatures (30–50 °C), the optimal temperature for hydrogen production by SSF in the MEC systems was 35 °C. Moreover, the contents of organic acids and reducing sugar significantly changed with varying in initial anolyte pH and temperature levels. The result indicates that a low initial anolyte pH value and high culture temperature was beneficial to hydrolysis of cellulose, and a high initial anolyte pH value and a moderate culture temperature to hydrogen production.     

Effect of nutrient supplementation on ethanol production in different strategies of saccharification and fermentation from acid pretreated rice straw

The effect of nutrient supplementation on ethanol production by recently selected thermotolerant yeast (Kluyveromyces marxianus NRRL Y-6860) was investigated in different strategies of saccharification and fermentation employing rice straw pretreated by dilute acid. Among the evaluated strategies, similar ethanol yields (Y_P/S ∼ 0.23 g g⁻¹) were obtained with or without nutrient addition. However, considering the whole process time, the strategy based on simultaneous saccharification and fermentation (SSF), without pre-hydrolysis, was assigned as the most suitable configuration due to the highest ethanol volumetric productivity (1.4 g L⁻¹ h⁻¹), about 2-fold higher in relation to the others. The impact of enzymatic preparation employed in this study was also evaluated on glucose fermentation in semi-synthetic medium. The enzymatic preparation affected both glucose consumption and ethanol production by K. marxianus NRRL Y-6860, but just in the absence of nutrients. Therefore, the enzyme type and loading should be carefully defined, not only by the capital costs involved, but also by the possibility of increasing the fermentation inhibitors.     

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.