复合微生物预处理玉米秸秆产沼气的试验研究

利用白腐菌、木霉菌以及白腐菌和木霉菌复合菌在相同的条件下对玉米秸秆进行预处理,对预处理后的秸秆进行厌氧发酵制取沼气。结果表明,利用微生物进行秸秆预处理能促进秸秆厌氧发酵产沼气的进程,提高产气量和产气效率,其中以混合菌预处理效果最好,产气量比未经预处理秸秆的产气量提高11.95%、产气时间提前6 d、产气高峰期提前16 d,容积产气率达到1.196 mL/(mL.d),原料产气率达到518.33 mL/g。仅利用白腐菌进行秸秆预处理也具有良好的效果,而利用木霉进行秸秆预处理对厌氧发酵的促进作用效果较差。说明利用木质素降解菌株进行秸秆预处理对提高秸秆的厌氧发酵效率具有重要的作用。     

紫外诱变筛选高效木质素降解菌株的研究

通过紫外诱变对白腐菌进行驯化培养,获得高效木质素降解菌,其LiP活力为600IU/mL,MnP活力为1600IU/mL。利用紫外诱变菌株S对玉米秸秆中的木质素进行降解试验,结果表明,木质素降解率为48.4%,比出发菌株的木质素降解率(42.6%)提高了13.6%。     

一株纤维素降解菌的筛选及其在沼气应用中的研究

利用实验室保存的细菌、真菌和从牛粪、猪粪中分离出来的多株菌株,对秸秆纤维素进行降解试验,从而筛选出了能够降解秸秆纤维素(降解率为43.75%)的优势菌株.用几株降解效果较理想的菌株处理秸秆,对处理后的秸秆进行沼气发酵,通过高效气相色谱仪对沼气成分进行分析,发现从牛粪中筛选出的N2菌株效果较好,发酵2周后,其产气中甲烷含量为62.48%(体积分数,下同),二氧化碳含量为31.83%,氮气含量为2.11%.通过生理生化鉴定,初步鉴定N2菌株为枯草杆菌(Bacillus subtilis).     

拟康氏木霉和白腐菌混菌发酵处理稻草秸秆的研究

以拟康氏木霉3.3002(Trichoderma pseudokoningii)和白腐菌5.776(Phanerochaete chrysosporium)的混合菌发酵处理稻草秸秆,并对处理结果进行了试验研究.研究结果表明,当接人拟康氏木霉与白腐菌时间间隔为3 d.接种液体积比为2 ml:2 ml,氮源为0.3%(质量分数)的(NH4)2SO4,发酵时间为8 d时,稻草秸秆纤维索降解率和木质素降解率分别为40.38%和31.52%,比单独使用拟康氏木霉(纤维素和木质素降解率分别为24.62%,13.78%)或白腐菌(纤维素和木质素降解率分别为6.96%,20.06%)处理稻草秸秆的效果有显著提高.     

白腐菌预处理稻草秸秆对Z28产纤维素酶的影响

研究了白腐菌预处理稻草秸秆对Z28产纤维素酶的影响.结果表明:在稻草秸秆上接种黄孢原毛平革菌,经过28d处理后,Z28发酵产纤维索酶,CMCase活力提高了31.4%,FPA活力提高了51.2%,β-葡萄糖苷酶活力提高了60.8%,未灭菌处理组β-葡萄糖苷酶的活力提高率远远大于灭菌处理组.     

高温纤维素酶产生菌的筛选鉴定及其酶性质研究

经过富集培养,用刚果红培养基透明圈法结合滤纸条降解法进行初筛,从堆腐过程中的双孢菇培养基质中分离出3株高温放线菌(A7、A16和A18)。3株高温放线菌进行摇瓶发酵培养后,用3,5-二硝基水杨酸法(DNS法)对其纤维素酶活性、滤纸酶活性和β-葡萄糖苷酶活性进行检测。3株菌中A18菌株产酶能力最强。对A18的羧甲基纤维素酶性质进行初步研究并对其进行生理生化特征研究和分子鉴定。A18羧甲基纤维素酶的最适作用温度为60℃,最适pH为7.0,发酵培养96h后酶活达最高。以16S rDNA序列为基础构建了相关种属菌在内的系统发育树,菌株A18在系统发育地位上属于稀有放线菌-拟诺卡氏菌属(Nocardiopsis),它和其他菌株的16S rDNA序列相似性最高为97%,可能为一潜在新种。A18可以利用鼠李糖、乳糖、纤维二糖、甘油和肌醇,不能利用阿拉伯糖、木糖和蔗糖作为碳源;在pH=7.0、温度45℃时生长状况最好。菌株A18可作为高温纤维素酶的产生菌进行进一步深入研究。     

木质素降解菌的筛选

采用愈创木酚法筛选出木质素降解菌X_2,并对其进行摇床培养,观察其生物学特性。研究表明:X_2在第8天生长最快,12d后生长速度开始下降;X_2生长最适温度为28℃,最适pH值为4.4;第10天木质素降解酶酶活最高,LiP为550.23u/mL,MnP为660.32u/mL,Lac活力很低,仅为20u/mL。此外,发现X_2的木质素的降解率也很高,在第35天达到43.31%。     

农作物秸秆生物法降解的研究

利用白腐菌对玉米秸秆中木质纤维素进行生物降解，研究木质纤维素的变化规律，确定了白腐菌对玉米秸秆进行生物降解预处理的适宜条件，降解周期为14d，降解预处理的固液比例为1：9，为秸秆快速产沼气做准备。     

厌氧消化菌群的筛选及其对高浓度玉米秸秆的厌氧消化

为了提高玉米秸秆类原料厌氧消化的产气率和底物利用率,从环境中筛选出了厌氧降解玉米秸秆产酸和产甲烷的优势菌群,该菌群的最高容积甲烷产率为0.73 m3/(m3.d),气体中的甲烷含量达到85%左右,底物产甲烷量为410 L/kg;以15%高浓度玉米秸秆为原料,该菌群的最大产酸能力为10 g/L,最高容积产气率为3.10m3/(m3.d),平均容积产气率为1.7 m3/(m3.d),平均甲烷含量为55%。研究结果明显高于报导过的相应数据。为高浓度玉米秸秆的高效厌氧消化利用提供了良好的微生物菌群应用基础。     

秸秆发酵产氢的碱性预处理方法研究

以麦秆、稻草和滤纸为发酵底料,以厌氧活性污泥为接种物,采用不同的预处理方法去除木质素并提高纤维素的降解率,从而提高其发酵产氢能力。试验表明对于相同的底料,经过NaOH预处理和纤维素酶解后的还原糖含量、总产气量、总产氢量和氢气浓度都要高于经过氨水预处理的底料,而未经过预处理的底料发酵产氢能力最差。利用10g经过NaOH预处理的麦秆和稻草,经纤维素酶解后在发酵产氢过程中的降解率分别为23.2%和12.5%,总产氢量分别为363.3mL和254.9mL,发酵产气中氢气浓度分别为23.8%和29.1%。发酵液相中主要产物为乙醇、乙酸和丁酸。     

Dilute acid pre-treatment of oilseed rape straw for bioethanol production

The objective of the research was to investigate the effect of biomass loading, acid concentration and pre-treatment time on the yield of sugars obtained after acid pre-treatment and enzymatic hydrolysis of oilseed rape (OSR) straw. The highest concentration of glucose (313.4 ± 7.53 mg g^?1 biomass) extracted after hydrolysis was achieved when OSR straw was pre-treated for 90 min; a glucan conversion efficiency of 81%. The highest concentration of sugars extracted immediately after pre-treatment was achieved with a pre-treatment time of 60 min. Pre-treatment energy efficiency in terms of total yield of sugars per MJ of energy consumed was higher when OSR straw was pre-treated for 60 min compared to 90 min even though the conversion of sugar extracted was lower at 60 min.     

Extrusion as a thermo-mechanical pre-treatment for lignocellulosic ethanol

Two physical pre-treatment methods, particle size reduction by grinding and thermo-mechanical extrusion, were evaluated as alternatives to traditional biomass pretreatments for lignocellulosic ethanol. Commonly available agricultural co-products wheat bran and soybean hull were the model substrates. Extrusion led to higher reducing sugar yields as compared to grinding for wheat bran, but not in the case of soybean hulls. The best combination of extrusion screw speed and maximum barrel temperature were 7 Hz/150 °C and 3.7 Hz/110 °C. The use of a solvent mixture (sodium hydroxide, urea, and thiourea) and calcium chloride solution in combination with extrusion treatment did not lead to improvement in reducing sugar yield. However, extensive washing to get rid of solvents and enzymatic inhibitors improved the conversion efficiency substantially, resulting in total reducing sugar yields of 60–73% and 25–36%, respectively, for wheat bran and soybean hull.     

Exploring alkaline pre-treatment of microalgal biomass for bioethanol production

We have investigated, for the first time, the alkaline pre-treatment of microalgal biomass, from the species Chlorococcum infusionum, using NaOH for bioethanol production. This pre-treatment step aims to release and breakdown entrapped polysaccharides in the microalgae cell walls into fermentable subunits. Three parameters were examined here; the concentration of NaOH, temperature and the pre-treatment time. The bioethanol concentration, glucose concentration and the cell size were studied in order to determine the effectiveness of the pre-treatment process. Microscopic analysis was performed to confirm cell rupturing, the highest glucose yield was determined to be 350 mg/g, and the maximum bioethanol yield obtained was 0.26 g ethanol/g algae using 0.75% (w/v) of NaOH and 120 °C for 30 min. Overall, the alkaline pre-treatment method proved to be promising option to pre-treat microalgal biomass for bioethanol production.     

Optimization of mechanical pre-treatment of Laminariaceae spp. biomass-derived biogas

Macroalgae have not met their full potential to date as biomass for the production of energy. One reason is the high cost associated with the pretreatment which breaks the biomass's crystalline structure and better exposes the fermentable sugars to anaerobes. In the attempt to overcome this technological barrier, the performance of a Hollander beater mechanical pretreatment is assessed in this paper. This pretreatment has been applied to a batch of Laminariaceae biomass and inoculated with sludge from a wastewater treatment plant. The derived biogas and methane yields were used as the responses of a complex system in order to identify the optimal system input variables by using the response surface methodology (RSM). The system's inputs considered are the mechanical pretreatment time (5–15 min range), the machine's chopping gap (76–836 μm) and the mesophilic to thermophilic range of temperatures (30–50 °C). The mechanical pretreatment was carried out with the purpose of enhancing the biodegradability of the macroalgal feedstock by increasing the specific surface area available during the anaerobic co-digestion. The pretreatment effects on the two considered responses are estimated, discussed and optimized using the tools provided by the statistical software Design-Expert v.8. The best biogas yield of treated macroalgae was found at 50 °C after 10 min of treatment, providing 52% extra biogas and 53% extra methane yield when compared to untreated samples at the same temperature conditions. The highest biogas rate achieved by treating the biomass was 685 cc gTS⁻¹, which is 430 cc gTS⁻¹ in terms of CH₄ yield.     

Effects of anaerobic pre-treatment on the degradation of dewatered-sewage sludge

Effects of anaerobic pre-treatment were evaluated on the dewatered-sewage sludge from a municipal wastewater treatment plant in order to improve its biodegradability through anaerobic digestion. The pre-treatment was conducted in laboratory scale at 25, 50 and 70 °C for an incubation time of two days. As a reference, sludge sample was also autoclaved at 121 °C for 20 min to determine the thermal effect to the subsequent sludge digestion. Characteristics of dewatered-sludge such as viscosity, pH and soluble chemical oxygen demand (SCOD) were affected by the pre-treatment. A higher SCOD after the pre-treatment did not necessarily imply an increase in methane yield, although initial biodegradability rate was improved. In fact, a ‘great’ improvement in SCOD concentration (up to 27%) was translated in only 8% increase in the methane yield (298 ± 9 and 276 ± 6 Nml CH₄ gVS_added^?1 for pre-treated and untreated samples, respectively). Increasing the anaerobic pre-treatment time from 12 h to 2 days at 50 °C led to an 11% improvement in methane yield. Methane content in biogas increased from an average of 65–69% for the pre-treated and untreated substrates, respectively. Volatile solids (VS) reduction increased from 42% to 51%. The overall digestion time was not affected by the pre-treatment but 90% of methane was produced in the first 12 days of incubation for 50 °C pre-treated samples whereas it took 2–5 days more for 25, 70 °C pre-treated and untreated sludge samples. In this study, thermophilic digestion was also found to be a better option in terms of faster digestion and higher VS-reduction, but it showed lower methane yield as compared to mesophilic digestion, i.e. 9% and 11% increment in methane yields for thermophilic and mesophilic digestions, respectively.     

Thermal pre-treatment of wet microalgae harvest for efficient hydrocarbon recovery

Botryococcus braunii, a green colonial microalga, is an unusually rich renewable source of hydrocarbons. In this study, wet microalgae harvest was thermally pretreated to enhance hydrocarbon recovery using a solvent extraction process. Samples containing a mixture of B. braunii and water were kept below 100 °C for 10 min. The observed hydrocarbon recovery was 97.8% at 90 °C. The extraction results suggest that the energy-intensive concentration and drying processes of the harvest could be eliminated. The proposed thermal pretreatment would revolutionize the conventional downstream processes.     

Enzymatic hydrolysis of pretreated soybean straw

In order to produce lactic acid, from agricultural residues such as soybean straw, which is a raw material for biodegradable plastic production, it is necessary to decompose the soybean straw into soluble sugars. Enzymatic hydrolysis is one of the methods in common use, while pretreatment is the effective way to increase the hydrolysis rate. The optimal conditions of pretreatment using ammonia and enzymatic hydrolysis of soybean straw were determined. Compared with the untreated straw, cellulose in straw pretreated by ammonia liquor (10%) soaking for 24 h at room temperature increased 70.27%, whereas hemicellulose and lignin in pretreated straw decreased to 41.45% and 30.16%, respectively.The results of infrared spectra (IR), scanning electron microscope (SEM) and X-ray diffraction (XRD) analysis also showed that the structure and the surface of the straw were changed through pretreatment that is in favor of the following enzymatic hydrolysis. maximum enzymatic hydrolysis rate of 51.22% was achieved at a substrate concentration of 5% (w/v) at 50 °C and pH 4.8 using cellulase (50 fpu/g of substrate) for 36 h.     

秸秆资源化利用技术分析

秸秆是重要的可再生的生物质资源,是仅次于煤、油、气的第四大能源.对我国各地的秸秆年产量、流向等方面进行了详细的调研,提出了秸秆资源化的方法.针对秸秆资源分布范围广阔而分散的特点,提出了农村区域性供能的设想.并通过对秸秆的燃烧机理的研究,为秸秆的能源化提供了一定的设计依据.     

Conversion of straw and similar agricultural wastes

Mainly the economic aspects prevent a far more extensive use of biomass, including straw as a fuel in energy supply.

During the latest years several straw fired plants have been put in operation, especially in Denmark, and they have demonstrated that both district heating and combined heat and power (CHP) production based on straw are technically possible.

However, experience has shown that a very precise research and development effort is necessary before the straw fired plants are competitive to traditional plants fired with fossil fuels, as to operational safety and economy.

The R & D activities ought first and foremost to aim at: 1) Reduction of costs connected to all processes from harvest to energy production, 2) wider know-how of the firing and combustion technical characteristics of straw, and 3) environmental conditions, including emissions and ash depositing problems.