超声波预处理协同黑曲霉水解玉米芯糖化工艺

以玉米芯为原料,采用超声波预处理和黑曲霉协同水解玉米芯制备还原糖。探讨了经过超声波预处理后原料的粒度、酶液用量、水解温度和水解时间对还原糖得率的影响,并采用响应面法建立二次回归模型对水解工艺进行了优化,在反应温度为56℃、反应时间为22.4 h、酶液用量为26 U/g时,还原糖的得率可达到36.58%,比在相同工艺条件下未经超声波处理的得率提高了13.41%。     

酸水解玉米芯制木糖醇

以玉米芯为原料 ,用酸水解 ,经中和、蒸发、脱色、离子交换、加氢、浓缩、结晶并将母液进行再处理可生产出木糖醇 .采用正交试验法研究了水解条件对木糖醇得率的影响 :在最佳生产工艺条件下 (水解压力 0 0 5MPa ,水解温度 12 0℃ ,加H2 SO4 浓度为 1 5 % ,水解时间 4h) ,木糖醇得率可达6 2 2 % .     

超声波诱导降解花生壳制备还原糖的研究

以花生壳为原料,采用超声波和NaHSO4.H2O固体酸水解制备还原糖。探讨超声波功率、反应时间、反应温度、固体酸用量对还原糖得率的影响。采用响应面法建立二次回归模型,并对水解工艺进行优化。研究结果表明,反应温度61.77℃,固体酸用量5.88%和反应时间124.14 min,还原糖的得率可达到80.72%,比在相同工艺条件下未经超声波协同处理的得率提高了27.38%。     

假丝酵母发酵玉米芯半纤维素水解液生产木糖醇

玉米芯是廉价的可再生资源,利用玉米芯半纤维素水解液发酵生产木糖醇,具有工艺简单、能耗小、产品质量好等特点。假丝酵母（Candida tropicalis）菌株经驯化后显著地提高了对水解液中发酵抑制物的耐受力,从而提高了木糖醇得率。确定发酵温度、初糖浓度、pH值、接种量、通气量等因素对发酵生产木糖醇的影响,并对其进行优化,优化结果为接种量10％（v／v）,种子龄24h,温度为30％,起始pH值为5．5,并且在发酵过程中补加适量氮源,木糖醇得率达61％。该方法大大降低了预处理的成本,有良好的应用前景。     

黑曲霉联合固体酸水解花生壳制备糠醛的研究

采用黑曲霉和WO3/SnO2固体酸联合水解花生壳制备糠醛,运用正交实验和响应面分析方法对主要因素进行了优化分析。酶解的正交实验结果显示:在原料粒度110目、固液比1:10、酶解温度为50℃、酶解时间为7h和酶液用量为30U/g干花生壳粉的条件下,制备戊糖的平均含量为14.87g·L-1。固体酸制备糠醛的响应面分析表明:当水解温度为163℃,水解时间134min,固体酸用量为6.4%时,糠醛的得率为68.52%,与未采用黑曲霉水解的工艺相比,糠醛的得率提高了15.69%。     

稀酸预处理玉米芯提取木糖的研究

通过单因素实验法和正交实验法优化了以玉米芯为原料制备木糖实验过程中各工艺参数,包括固液比、酸浓度、处理温度以及处理时间。结果表明,稀酸预处理过程各因素对玉米芯木糖提取率影响程度由大到小的顺序为:处理温度酸浓度处理时间。且在降低酸浓度和减少反应时间的情况下,仍可使木糖得率达到较高的水平,优化的实验条件为:固液比1∶10,酸浓度1. 2%,处理温度120°C,处理时间90 min。在此条件下,木糖得率可达86. 36%。     

微波固体酸联合水解棉籽壳制备还原糖的研究

以棉籽壳为原料,采用微波和固体酸协同水解制备还原糖。探讨了微波功率、固体酸用量、反应时间、反应温度、液固比对还原性糖得率的影响。采用响应面法建立二次回归模型,并对水解工艺进行了优化。研究结果表明,当微波功率461.91W,固体酸用量6.46%,反应时间2.99h,反应温度100℃,液固比为18∶1时,还原糖的得率可达到62.49%。     

稀酸预处理对玉米秸秆纤维组分及结构的影响

研究了稀硫酸预处理对玉米秸秆化学组成变化及纤维素酶水解得率的影响,并采用扫描电镜(SEM)、X射线衍射仪(XRD)、红外光谱(IR)和热重分析(TG)对玉米秸秆纤维结构特性进行了分析。结果表明随着硫酸浓度的增大、温度的升高和时间的延长,纤维素和木质素含量有所增加,而半纤维素含量大幅度降低,且预处理后纤维素酶水解得率也逐渐增大。当处理条件为硫酸质量分数0.75%、温度150℃、时间80 min时,半纤维素降解率为98.02%,所得固体渣纤维素酶水解得率为66.95%(纤维素酶用量20 FPUI/g纤维素)。稀酸预处理后玉米秸秆纤维表面和细胞壁受到不同程度的破坏,表面积增大,孔洞增加,纤维素的结晶度降低,有利于纤维素酶水解作用的进行。     

酸水解玉米芯制木糖醇

介绍了将玉米芯采用酸水解法生产木糖醇的生产工艺,研究了水解条件对木糖醇得率的影响,确定了最佳生产工艺条件。     

蒸汽爆破强度对玉米芯酶水解制备低聚木糖的影响

以玉米芯为底物,采用蒸汽爆破预处理与内切木聚糖酶定向酶水解相结合制取低聚木糖。基于高效阴离子交换色谱法对聚合度为2～6的低聚木糖组分的准确定量分析,研究蒸汽爆破预处理反应强度系数及其主要参数(反应温度和维压时间)对玉米芯定向酶水解制取低聚木糖的组成分布及产品得率的影响规律,确立最佳蒸汽爆破预处理条件。蒸汽爆破-定向酶解效果综合评价的结果表明,玉米芯最佳的蒸汽爆破预处理条件是反应强度系数3.76、反应温度200℃、维压时间390s。此时低聚木糖得率可达到最高值20.8%,且主要组分以木三糖、木四糖和木二糖为主,含量分别占总得率的43.5%、21.3%和18.6%。     

Xylitol production on sugarcane biomass hydrolysate by newly identified Candida tropicalis JA2 strain

Xylitol is a building block for a variety of chemical commodities, besides being widely used as a sugar substitute in the food and pharmaceutical industries. The aim of this work was to develop a microbial process for xylitol production using sugarcane bagasse hydrolysate as substrate. In this context, 218 non-Saccharomyces yeast strains were screened by growth on steam-exploded sugarcane bagasse hydrolysate containing a high concentration of acetic acid (8.0 g/L). Seven new Candida tropicalis strains were selected and identified, and their ability to produce xylitol on hydrolysate at low pH (4.6) under aerobic conditions was evaluated. The most efficient strain, designated C. tropicalis JA2, was capable of producing xylitol with a yield of 0.47 g/g of consumed xylose. To improve xylitol production by C. tropicalis JA2, a series of experimental procedures were employed to optimize pH and temperature conditions, as well as nutrient source, and initial xylose and inoculum concentrations. C. tropicalis JA2 was able to produce 109.5 g/L of xylitol with a yield of 0.86 g/g of consumed xylose, and with a productivity of 2.81 g·L·h, on sugarcane bagasse hydrolysate containing 8.0 g/L acetic acid and177 g/L xylose, supplemented with 2.0 g/L yeast nitrogen base and 4.0 g/L urea. Thus, it was possible to identify a new C. tropicalis strain and to optimize the xylitol production process using sugarcane bagasse hydrolysate as a substrate. The xylitol yield on biomass hydrolysate containing a high concentration of acetic acidobtained in here is among the best reported in the literature.     

乙酸预浸渍用于小麦秸秆蒸汽预处理生产纤维素乙醇

通过改进传统蒸汽爆破预处理方法,利用两步法对小麦秸秆进行预处理.在蒸汽爆破前加入乙酸溶液预浸渍,有效的提高了后续同步糖化发酵的水平.采用乙酸预浸渍气爆预处理后的整个草浆和固形物同步糖化发酵乙醇浓度分别达到25.Sg/L、30.6g/L,分别达到葡萄糖乙醇理论产率的77％、90％;相比传统气爆,草浆和固形物同步糖化发酵乙醇浓度分别仅为17.5g/L、29.2g/L,葡萄糖转化为乙醇仅分别达到理论产率的63％、85％.通过提高固形物浓度到20％,乙酸预浸渍气爆处理后的固形物同步糖化发酵乙醇浓度可达67.3g/L,达到葡萄糖乙醇理论产率的96％.乙酸预浸渍气爆预处理能有效的减少抑制物的生成,提高木质纤维素结构破坏程度以及糖的回收率.     

驯化和胶囊包裹的假丝酵母LF04发酵玉米芯水解液生产木糖醇(英文)

玉米芯的酸水解液是木糖醇生产的重要原料,但是该水解液中含有糠醛、酚类等对后续微生物发酵有毒害作用的化合物。本研究从土壤中分离了一株似假丝酵母LF01,通过驯化和微胶囊包裹来提高其对水解液的抗性。结果表明通过多次驯化并进行包裹的假丝酵母LF04能在玉米芯水解液中不经任何脱毒处理发酵木糖生产木糖醇。在pH5.5 溶氧为 0.15vvm 的条件下发酵 88h,木糖转化率为 76%,木糖醇浓度达 61.768g/L。远高于其出发菌株。该结果表明采用该方法有望用于木糖醇的工业化生产。     

Xylitol production from rice straw hemicellulose hydrolyzate by polyacrylic hydrogel thin films with immobilized Candida subtropicalis WF79

Xylose from rice straw hemicellulose hydrolysate was fermented for xylitol production using Candida subtropicalis WF79 cells immobilized in polyacrylic hydrogel thin films of 200 mum thickness. Cell immobilization was conducted by first suspending the yeast cells in a mixture of 2-hydroxyethyl methacrylate (HEMA, hydrophilic monomer), polyethylene glycol diacrylate (PEG-DA, crosslinking agent), and benzoin isopropyl ether (photoinitiator). The mixture was then allowed to form polyacrylic hydrogel thin films, between two pieces of glass sheets, by UV-initiated photopolymerization. The hemicellulose of rice straw was hydrolyzed using dilute sulfuric acid at 126 degrees C. The hydrolysate was neutralized with calcium hydroxide. After separating the solid residues and calcium sulfate precipitates by filtration, the hydrolysate was treated with charcoal to partially remove potential inhibitory substances, followed by vacuum concentration to obtain solutions of desired xylose concentrations for yeast fermentation. The thin films with immobilized yeast cells were submerged in the xylose solution from rice straw hydrolysate for fermentation in an Erlenmeyer flask. The maximum yield was 0.73 g of xylitol per gram of xylose consumed. In the 52.5-day long durability test, after 40 d of repeated batchwise operation, the fermentation activities of the cell immobilized in thin films began to decline to a yield of 0.57 g/g at the end.     

基于酶法制备的凉薯饮料配方优化及品质测定

;凉薯为主要原料,羧甲基纤维素钠、白砂糖、柠檬酸、木糖醇为辅料,凉薯经液化、糖化后,使用单因素及正交试验研究各辅料对凉薯饮料品质的影响,并对凉薯饮料总酸、总糖、可溶性固形物进行测定。凉薯饮料最优配方为：白砂糖添加量8%、柠檬酸添加量0.12%、木糖醇添加量1%、CMC-Na添加量0.18%。在此最优配方条件下,凉薯饮料感官评分为86.4分,总酸含量为0.55%,总糖含量为7.97%,可溶性固形物含量为11.0%,pH为4.3,饮料组织均匀、酸甜适中、回味清爽,呈淡黄色,具有凉薯的独特风味。     

连翘叶固体饮料的研制及活性成分测定

目的 以连翘叶、木糖醇、柠檬酸、麦芽糊精为主要原料,开发一种连翘叶固体饮料。方法 通过单因素、正交实验,以优、中、差三个质量等级对产品的色泽、气味、滋味、状态四个方面进行感官评判,通过模糊数学法处理数据,得到连翘叶固体饮料最佳配方。根据固体饮料的颗粒状态和溶解速度,选取固体饮料产品颗粒粒径;直接干燥法测定固体饮料的水分含量;以高效液相色谱法测定固体饮料中连翘苷和连翘酯苷A的含量。结果 连翘叶固体饮料最佳配方为连翘叶提取物4g,木糖醇5g,柠檬酸0.2g,麦芽糊精4g;固体饮料产品颗粒粒径为40目;水分含量为6.1%,符合国标要求;固体饮料中连翘苷和连翘酯苷A的含量分别为0.34%和0.27%。结论 得到的连翘叶固体饮料颗粒饱满,溶解迅速,冲调后呈透明的黄色,气味淡雅,酸甜适口,本实验可为连翘叶固体饮料的开发提供支持。     

Production of highly concentrated xylitol by Candida magnoliae under a microaerobic condition maintained by simple fuzzy control

Microbial production of xylitol from xylose was investigated using Candida magnoliae. In particular, the effect of the oxygenation condition on the xylitol production yield was examined and the significance of maintaining a microaerobic condition was demonstrated. A simple system of fuzzy logic control (FLC) was devised to maintain the microaerobic condition in the xylitol production phase by regulating the proportion of air (air flow rate) supplied to the fermentor. The input variables to the fuzzy control system were the dissolved oxygen (DO) concentration in the culture broth and the CO2 concentration in the exit gas. A batch cultivation test using the FLC system confirmed the importance of maintaining a constant microaerobic condition throughout the xylitol production phase, and indicated it would be advantageous for this phase to be prolonged. An intermittent fed-batch culture was therefore carried out. The FLC system allowed a constant microaerobic condition to be maintained, resulting in minimal cell mass production and constant xylitol accumulation in the culture medium. As a consequence, a very high xylitol concentration of 356 g/dm3 could be attained. The xylitol yield in the fed-batch culture was 0.75, which corresponded to 82% of the theoretical yield.     

碱预处理对慈竹机械浆酶解的影响

以慈竹机械浆为研究对象,分别采用NaOH和NaOH加H2O2两种方法对原料进行预处理,考察预处理条件对酶解还原糖产率的影响。得到NaOH最佳预处理条件为:预处理温度90℃、固液比1∶5g/mL、时间2h、NaOH用量12%(g/g绝干)。在此最佳条件下,慈竹机械浆半纤维素保留率为87.92%、纤维素保留率为90.29%、木质素脱除率为43.24%;在pH4.8、加酶量20FPU/g预处理后底物、反应温度50℃的条件下酶解24h,还原糖产率为30.36%。扫描电镜观察显示,经碱性预处理过的慈竹机械浆变得粗糙而多孔,增加了纤维素酶的吸附位点,酶解速率加快。     

采用响应面法优化木糖醇发酵培养基

将Plackett-Burman和响应面设计相结合,对木糖醇发酵培养基进行了优化。结果表明,初始木糖浓度、酵母膏添加量以及MgSO4.7H2O浓度是影响木糖醇转化率的主要因素。优化得到的培养基组成为(g/L)木糖100.7,酵母膏5.302,NaCl6.0,MgSO4.7H2O0.379,KH2PO43,(NH4)2HPO44;通气条件为装液量100mL/250mL。此条件下木糖醇的转化率为0.784g/g。