蒸汽爆破预处理对玉米芯酶水解的影响

采用不同的蒸汽爆破条件对玉米芯进行预处理,研究蒸汽爆破对玉米芯理化性质和酶水解的影响。结果表明:蒸汽爆破条件为1.4 MPa,300 s时,玉米芯酶水解液中总糖浓度最高为58.17 g/L。蒸汽爆破预处理主要引起半纤维素大量降解,但过高的压力或过长的保压时间会使木糖进一步降解,从而使玉米芯水解糖得率降低。X-衍射结果表明:经1.4 MPa,300 s蒸汽爆破的玉米芯结晶度由对照的24.49%提高到43.09%。由扫描电镜可知,蒸汽爆破可提高玉米芯的孔隙度和表面积,从而提高酶水解效率。     

汽爆玉米秸秆产乙醇的补料同步糖化发酵优化

为提高反应系统中的底物浓度,减少酶用量,以蒸汽爆破预处理的玉米秸秆及高性能的酵母菌株Y5进行补料同步糖化发酵研究。通过同步糖化发酵策略的优化,经两次补料使反应体系底物浓度提高至25.7%,同步糖化发酵72h,即可获得41.7g/L的乙醇浓度,综合转化率64%。同时,纤维素酶及β-葡萄糖苷酶用量分别可降至7FPU/(g纤维素)及7IU/(g纤维素)。     

提高菌株KE6-12对爆破秸秆同步糖化发酵适应性研究

利用可消化戊糖的菌株KE6-12进行发酵,以提高蒸汽爆破预处理玉米秸秆纤维素乙醇产率。通过调节预处理液的pH、发酵温度及采取补料策略提高菌株KE6-12对蒸汽爆破处理玉米秸秆同步糖化发酵的适应性。研究发现,在pH为5.0,温度为35℃条件下,经洗涤的预处理样品发酵96 h后,乙醇转化率可达到76%(相对于原料中葡萄糖含量);未洗涤样品仅为25%,将pH调至5.5,发酵144 h后转化率可提高至68%。采用补料策略B(发酵初加入纤维素酶,并分数批加入预处理后样品),将发酵温度降至30℃,144 h后发酵液中乙醇浓度达到27.6 g/L,转化率达到理论值的78%。通过调整发酵工艺,提高了可消化戊糖菌株的乙醇产率,对工业化应用具有一定的借鉴意义。     

未脱毒汽爆玉米秸秆高底物浓度的同步糖化和乙醇发酵

为取消蒸汽爆破预处理玉米秸秆水洗脱毒步骤和提高乙醇发酵的乙醇浓度,利用专利菌株酿酒酵母Y5,对蒸汽爆破预处理玉米秸秆不经脱毒处理,直接进行同步糖化和发酵(SSF)。蒸汽爆破玉米秸秆的浓度30%,同步糖化和发酵的时间96 h,100 m L、3000 m L反应器和5L发酵罐的乙醇浓度分别达到50.0、47.8、47.5 g/L。研究结果表明,菌株Y5在纤维素乙醇生产中对简化生产工艺、降低设备投资、减少水消耗、降低生产成本具有重要的应用前景。     

四种北方能源草本植物的乙醇甲烷联产潜力研究

乙醇发酵生产过程中,针对蒸汽爆破预处理能源草提出高底物同步糖化发酵策略。当底物浓度为20%(质量分数)时,经批式补料乙醇发酵最终4种能源草本植物的最终乙醇产量分别达到15、13、16、15 g/L。随后的甲烷潜力测试结果表明:汽爆冰草与汽爆披碱草有较好的产甲烷能力,其甲烷产量分别达到562.4 m L和546.7 m L,相对应的甲烷产率为360.05 m L/g VS和382.04 m L/g VS。综合实验结果分析,相比于其他3种能源草本植物,冰草具有较高的全组分利用率及清洁能源产量。     

稻草秸秆多酶水解条件研究

研究了稻草秸秆经过稀酸预处理后的酶水解条件,得到用于生产燃料乙醇的还原糖。试验结果表明:稻草秸秆经1%(w/w)的稀硫酸浸润,液固比(v/w)为5∶1,在121℃条件下处理60min后,每克稻草秸秆的初始水解还原糖得率达到0.187g。预处理后,在45℃,pH4.8,120r/min,48h条件下,采用酶的添加量最优配比(每克秸秆添加木聚糖酶217IU,纤维素酶5.13FPU,果胶酶25μ,β-葡聚糖酶500μ,淀粉酶150μ)时,水解产生的还原糖浓度达到最大值84.22g/L,原料水解率为41.19%。在酶水解糖化过程中,当MgSO4,Tween80的添加量分别为0.0001,0.005g时对纤维素酶有激活作用。     

绿色木霉对膨化玉米秸秆糖化效果的研究

以膨化玉米秸秆为原料,利用绿色木霉对膨化玉米秸秆进行糖化处理,研究吐温-80添加量、发酵温度、底物浓度、加酶量、MgSO4添加量对糖化过程的影响。运用二次回归正交组合试验设计,确定出最佳的糖化条件。结果表明,吐温-80添加量为1%(体积分数),温度为36℃,底物浓度为80 g/L,加酶量为每克底物40U,MgSO4添加量为0.4%时,膨化玉米秸秆的糖化效果最佳,糖化率为23.9%。     

甘蔗渣的碱催化甘油水溶液预处理

建立了一种木质纤维素的碱催化甘油水溶液预处理方法以期选择性分离组分和提高底物的可酶解性。实验确定了碱催化甘油水溶液预处理甘蔗渣的条件为：温度180℃、NaOH添加量7%、反应时间45 min以及甘油水溶液浓度80%。在该条件下,甘蔗渣的纤维素和半纤维素保留率分别为93.0%和83.4%,而木质素脱除率接近80%,达到了理想的组分分离效果。预处理后底物（20 g/L）在CTec2酶载量10 FPU/g干基下水解72 h酶解率为79.6%,表明预处理后底物具有较好的可酶解性。利用现代分析技术解析了甘蔗渣预处理前后的组成结构演变规律,初步探明了碱催化甘油水溶液预处理有效提升生物质原料可酶解性的原因。     

甜高粱渣分批补料酶水解生产高浓度糖

为了提高水解液中糖浓度,降低后续乙醇蒸馏成本,以低温碱处理的甜高粱渣为底物,研究分批补料糖化工艺对高浓度底物酶解的影响,采用扫描电镜(SEM)和红外光谱仪(FT-IR)对底物结构变化进行分析。结果表明:碱预处理可去除大部分的木质素,使纤维素暴露到表面,增加纤维素酶水解的可及性。甜高粱渣酶解的初始底物浓度为9%(w/v),在酶解8、24、48 h后分别补料8%、7%和6%构成四组酶解体系,分批补料水解最高固含量30%,酶用量为9.96 FPU/g底物的体系,酶解120 h后,葡萄糖和木糖浓度分别达到102.52 g/L和29.48 g/L,葡聚糖和木聚糖转化率分别为52.16%和40.45%。     

高浓度红薯醪SSF燃料乙醇过程中底物抑制的调节

红薯干经粉碎、液化处理后得到淀粉含量为230g/kg的高浓度红薯醪,利用工业酵母Saccharomyces cereviseATCC 6508同步糖化发酵(SSF)生产燃料乙醇。通过改变糖化酶的添加剂量调节发酵过程中糖化速率,控制醪液中葡萄糖浓度的变化。发酵前期严格控制底物抑制对细胞生长速率的影响,通过较高的细胞浓度保障发酵后期发酵速率,减轻产物抑制对发酵过程的影响。实验发现在0.2、0.4、0.6和0.8g/kg(糖化酶/红薯干粉)糖化酶添加量下,发酵过程中葡萄糖浓度被严格控制在强烈抑制的浓度水平以下(100g/kg),1.0g/kg剂量下醪液中葡萄糖浓度长时间高于100g/kg,底物抑制严重;发酵后期在0.2、0.4和0.6g/kg剂量下,由于糖化酶活性降低,糖化速率成为发酵速率的限制因素。综合分析糖化酶的最佳剂量为0.8g/kg,该剂量下既能严格控制底物抑制水平,同时保持发酵后期较高糖化速率,发酵终点乙醇浓度达118.23g/kg(16.12%,v/v),发酵时间为72h。     

The steam explosion pretreatment and enzymatic hydrolysis of wheat bran

This article focused on the saccharification of wheat bran with steam explosion pretreatment and enzymatic hydrolysis. Wheat bran was pretreated with steam explosion to improve saccharification with enzymatic hydrolysis, and a maximum reducing sugar yield reached 194.6 mg/g (dry), which was about 63% higher than that of the wheat bran without pretreatment. Electronic microscope scanning and infrared spectroscopy showed that steam explosion with low pressure destroyed the structure and promoted the enzymatic hydrolysis of wheat bran effectively. Further, higher pressure produced harmful substances to hinder the saccharification and subsequent fermentation rather than increase saccharification ability of blasting bran.     

New process of maize stalk amination treatment by steam explosion

Amination treatment of straw proceeds slowly at the low environmental temperatures. Although the aqueous ammonia has a relatively good effect, it has high volatility and an irritant odor. Steam explosion has the advantage of short reaction time, but it cannot improve the nitrogen content of the straw for animal feed. A new process combined with the two methods for maize stalk pretreatment was studied to improve its nutritive value. The results showed that nitrogen sources coupled with steam explosion modified the treated materials. Except for urea, other nitrogen sources promoted the degradation of hemicellulose and the increase of the soluble sugars content. Decrease of hemicellulose treated with 5% (NH₄)₂SO₃ was highest (58.0%), but no significant changes were detected in cellulose and lignin content using chemical methods after nitrogen source addition. Compared with steam explosion pretreatment, amination by steam explosion increased the nitrogen content of maize stalk. The highest total nitrogen content (2.30%) was obtained by adding urea. The treatment of 5% (NH₄)₂SO₃ led to the highest retention of added nitrogen (84.0%) and 15% NH₄OH led to the lowest percentage of retention (18.1%). Amination by steam explosion effectively increased the potential digestibility of DM, and the maximum digestibility value (71.2%) was obtained when 5% (NH₄)₂SO₃ was added. Amination by steam explosion shortened the amination time and was a rapid and effective method of improving the nutritive value of straw.     

One-factor-at-a-time (OFAT) optimization of hemicellulases production from Fusarium moniliforme in submerged fermentation

Hemicellulose degrading enzymes play an important role in bioconversion of lignocellulosic and agro-industrial wastes. In this study, production of hemicellulase by six fungal isolates was determined under submerged culture using corn cobs xylan as a carbon source and enzyme inducer at different incubation periods. The results indicated that Alternaria tenuis showed the lowest enzyme productivity (156.95 ± 2.07U/l) while the highest enzyme production (2,594.44 ± 62.25 U/l) was obtained by Fusarium moniliforme. One-factor-at-a-time revealed maximum enzyme productivity of 10,950.11 ± 98.45 U/l at corn cobs xylan (6 g/l), yeast extract (4 g/l), inorganic salts (1.5 g/l KH₂PO₄, 1.0 g/l MgSO₄.7H₂O, 0.2 g/l CaCl₂, 0.4 g/l FeSO₄.7H₂O, and 0.3 g/l MnSO₄.5H₂O), initial pH (5), initial inoculum size (4%), 150 rpm, and temperature (30°C) in a submerged fermentation process.     

Statistical Modeling And Optimization Of Pretreatment For Fermentable Sugars Production From Cotton Gin Waste

Bioethanol is produced from lignocellulosic materials, such as agricultural waste, forest residues, etc. In this study, cotton gin waste was utilized to produce fermentable sugars through an effective pretreatment method. Autoclaving, steam explosion, and liquid hot water pretreatments were compared for their effectiveness in disruption of the lignocellulose matrix. Autoclaving was proved to be an effective pretreatment method in terms of maximum reducing sugar production. The Box–Behnken design (BBD) was employed in the optimization of autoclaving pretreatment. Slurry density (X₁, g/mL), temperature (X₂, °C), and time (X₃, min) were chosen as the independent variables and the total reducing sugar concentration (Y, mg/L) as the dependent variable (response). The total reducing sugar production from cotton gin waste was found to be 511.48 mg/L experimentally, at an optimum slurry density of 0.50 g/mL, a temperature of 138°C, and a time of 11 min.     

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。     

榨糖收贮模式玉米秸秆蒸汽爆破预处理条件优化

使用蒸汽爆破法处理榨糖收贮玉米秸秆榨渣,观察不同蒸汽爆破压力和维压时间下纤维素、半纤维素、木质素（三大素）及纤维素酶水解得率的变化。榨渣三大素含量不同程度下降,半纤维素下降最多,其次是木质素,而纤维素下降最少。处理后进行的水解实验显示压力与维压时间的增加会导致纤维素水解酶得率有所提高,但压力增加对纤维素水解酶影响较小,维压时间对纤维素水解酶的影响较为突出。考虑经济成本的前提下选择1.2 MPa,10 min维压时间为最佳条件,其中纤维素含量为34.42%、半纤维素4.01%、木质素17.09%及纤维素酶水解得率为68.3%。     

Investigating the potential for energy,fuel, materials and chemicals production from corn residues (cobs and stalks) by non-catalytic and catalytic pyrolysis in two reactor configurations

The results of thermogravimetric analysis (TGA), non-catalytic and catalytic pyrolysis of corn cobs and corn stalks are reported in this paper. Pyrolysis took place in two different reactor configurations for both feedstocks: (1) fast pyrolysis in a captive sample reactor; and (2) non-catalytic slow pyrolysis and catalytic pyrolysis in a fixed-bed reactor. Experiments were carried out in atmospheric pressure at three temperatures: low temperature (360–380 °C), medium temperature (500–600 °C) and at high temperature (600–700 °C). The results of the experimental study were compared with data reported in the literature. Investigating the potential of corn residues for energy, fuel, materials and chemicals production according to their thermochemical treatment products yields and quality, it can be stated that: (a) corn stalks could be suitable raw material for energy production via gasification at high temperature, due to their medium low heating value (LHV) of pyrolysis gas (13–15 MJ/m³); (b) corn cob could be a good solid biofuel, due to the high LHV (24–26 MJ/kg) of the produced char; (c) additionally, corn cobs could be a good material for activated carbon production after being activated or gasified with steam, due to its high fixed carbon content(～74 wt%); (d) liquid was the major pyrolysis product from catalytic pyrolysis (about 40–44 wt% on biomass) for both feedstocks; further analysis of the organic phase of the liquid products were hydrocarbons and phenols, which make them interesting for chemicals production.     

Biohydrogen production from pretreated corn cobs

In this study, the co-fermentability of four different pretreated corn cob streams at different mixing ratios was assessed. The four streams, denoted DP, DS, HP, and HS, were: two dilute acid pretreatment comprising one purge and one squeeze and two high pressure autohydrolysis comprising one purge and one squeeze. The “Purge” stream was taken from the steam percolation reactor during cooling and the “Squeeze” stream was recovered from the cooked biomass with a pressing step. In addition, the impact of furfural and 5-hydroxymethylfurfural (HMF) on biohydrogen production potential was evaluated. The DP:DS mix at 50:50 by volume achieved the maximum H₂ yield of 265 (mL/gCOD sugars consumed). Furfural at concentrations of 0.21–1.09 g/L had no impact on H₂ production rates and yields and HMF was below the inhibitory threshold of 0.14 g/L. A positive correlation was observed between the monomeric-to-polymeric sugars ratio and H₂ production rates and yields.     

Synergistic mechanism of steam explosion combined with fungal treatment by Phellinus baumii for the pretreatment of corn stalk

Pretreatment was the essential step for industrial application of lignocellulosic biomass. Combination of steam explosion and fungal treatment was conducted, and synergistic mechanism of the combined pretreatment was evaluated in terms of pore size distribution, crystallinity index, chemical compositions and enzymatic hydrolysis. The results showed that steam explosion destroyed the rigid structure of corn stalk, increased pore size and porosity, and exposed crystalline component of cellulose. Steam explosion broke the lignin-carbohydrate-complex structure of lignocellulosic biomass and facilitated the fungal treatment. Phellinus baumii could selectively degrade 34.7% and 36.58% of lignin for 1.4 MPa and 1.7 MPa steam-exploded corn stalk, respectively. As a result, the highest glucose yield of corn stalk pretreated by the condition of 1.7 MPa steam explosion associated with 21 d P. baumii reached 313.31 g kg⁻¹, which was 2.88 and 1.32 times higher than that of the untreated corn stalk and the 1.7 MPa steam-exploded corn stalk, respectively. The combined pretreatment enhanced the enzymatic hydrolysis, which was a promising technology that might be explored as alternative to the existing pretreatment.     

Combined ethanol and methane production from switchgrass (Panicum virgatum L.) impregnated with lime prior to steam explosion

Pretreatments are crucial to achieve efficient conversion of lignocellulosic biomass to soluble sugars. In this light, switchgrass was subjected to 13 pretreatments including steam explosion alone (195 °C for 5, 10 and 15 min) and after impregnation with the following catalysts: Ca(OH)₂ at low (0.4%) and high (0.7%) concentration; Ca(OH)₂ at high concentration and higher temperature (205 °C for 5, 10 and 15 min); H₂SO₄ (0.2% at 195 °C for 10 min) as reference acid catalyst before steam explosion. Enzymatic hydrolysis was carried out to assess pretreatment efficiency in both solid and liquid fraction. Thereafter, in selected pretreatments the solid fraction was subjected to simultaneous saccharification and fermentation (SSF), while the liquid fraction underwent anaerobic digestion (AD). Lignin removal was lowest (12%) and highest (35%) with steam alone and 0.7% lime, respectively. In general, higher cellulose degradation and lower hemicellulose hydrolysis were observed in this study compared to others, depending on lower biomass hydration during steam explosion. Mild lime addition (0.4% at 195 °C) enhanced ethanol in SSF (+28% than steam alone), while H₂SO₄ boosted methane in AD (+110%). However, methane represented a lesser component in combined energy yield (ethanol, methane and energy content of residual solid). Mild lime addition was also shown less aggressive and secured more residual solid after SSF, resulting in higher energy yield per unit raw biomass. Decreased water consumption, avoidance of toxic compounds in downstream effluents, and post process recovery of Ca(OH)₂ as CaCO₃ represent further advantages of pretreatments involving mild lime addition before steam explosion.