利用动力学模型探讨底物浓度对生物产氢的影响

运用间歇实验方法,以葡萄糖为底物,在浓度为0-300g／L时,研究了底物浓度对混合细菌发酵产氢的影响．结果表明,在35℃和初始pH7．0时,当底物浓度为0～25g／L时,混合细菌发酵葡萄糖的最大累积产氢量和产氢速率都随着底物浓度的增加而增加．当底物浓度为25g／L时,最大累积产氢量和产氢速率都是最高的,分别为426．8mL和15．1mL／h．当底物浓度为2g／L时,比产氢率和底物降解率最大,分别为384．3mL／g葡萄糖和97．6％．修正的Logistic模型能很好地描述本研究中累积产氢量随时间的变化规律．Han-Levenspiel模型能很好地描述本研究中底物浓度对产氢速率的影响．     

类产碱假单胞菌XW-40发酵-生物转化级联产生D-脯氨酸

建立了一个新颖的用于产生D-脯氨酸的发酵-生物转化过程.发酵过程中,以DL-脯氨酸为发酵前体,类产碱假单胞菌XW-40利用L-对映体诱导产生脯氨酸脱氢酶,D-对映体完全保留.在最优条件下,发酵阶段产生6 g/L D-脯氨酸.生物转化过程中,细胞不经分离,发酵液直接作为反应介质.采用分批补料策略实现DL-脯氨酸中L-对映体的转化.DL-脯氨酸单批补料浓度为10 g/L,补料次数达到5批.通过发酵和生物转化的级联,累积的D-脯氨酸浓度达到31 g/L,ee99%.推测了生物转化过程中D-脯氨酸产生的反应机理.     

酯化反应精馏体系的相平衡计算

１前言由于反应精馏过程需同时遵循质量作用定律和分离原理,过程影响因素复杂,用数学模拟的方法对其过程进行研究己成为一种重要的方法。为求解模型方程必然涉及到一些基础数据的计算,如求解平衡级模型ＭＥＳＨＲｎｇ组（物料衡算Ｍ方程、热量衡算Ｈ方程、相平衡Ｅ方程、组分归一Ｓ方程及反应动力学Ｒ方程）的过程中,会遇到相平衡常数、烩值等热力学性质的计算;在求解非平衡级模型ＭＥＲＱｉｅ组（物料衡算Ｍ方程、热量衡算ＥＡＮ。传递速率Ｒ方程吸界面相平衡Ｑ方程）的过程中,会遇到传质系数、传热系数、有效相界面积等传递性质的计…     

溶液间歇结晶过程成核与生长阶段的定量识别

为定量识别溶液间歇结晶过程中的成核和生长阶段,基于晶粒数目和粒度的变化对粒度分布(CSD)的二阶和三阶矩量影响程度的不同,定义并关联了无因次变量K和K^*.添加晶种KNO₃-H₂O溶液结晶过程模拟计算的结果表明,K和K^*值均呈先降后升的变化趋势,成核时单调下降,生长过程中单调上升;且K与K^*值较接近.测定了KNO₃-H₂O溶液自发成核结晶过程中溶液浓度和透光率的变化,用K^*判据定量识别出成核阶段和生长阶段,并与晶体线性生长速率模型检验的结果相吻合.K值的计算依赖于CSD和结晶动力学参数,而K^*作为成核和生长阶段的模型判据,由实验测定的溶液浓度和透光率计算得到.     

中药材三七提取液近红外光谱的支持向量机回归校正方法

提出近红外光谱的支持向量机回归校正建模方法.以中药材三七渗漉提取液为实际分析对象,对其近红外光谱数据进行预处理和主成分分析后,用支持向量机回归算法建立人参皂苷R_g1,R_b1和R_d以及三七总皂苷的近红外光谱校正模型.以R_g1,R_b1和R_d的HPLC测定值及三七总皂苷的比色法测定值为参照,将本文方法与偏最小二乘回归和径向基神经网络建模方法相比较,结果表明,本文所建模型的预测准确性优于后两者,可推广应用于中药提取过程的近红外光谱分析.     

近红外光谱法在红曲菌固态发酵过程参数检测中的应用

研究了近红外光谱技术快速检测红曲菌固态发酵过程参数水分含量和pH值的可行性。针对传统基于间隔策略波长选择方法忽略非线性因素的缺点,采用一种基于最小二乘支持向量机(Least squares support vector machines,LS-SVM)非线性模型的波长筛选算法:联合区间最小二乘支持向量机(Synergy interval least squares support vector machines,siLS-SVM),并将新算法与相关系数法、iPLS算法、siPLS算法对比。实验结果显示,联合siLS-SVM算法和LS-SVM模型取得了最好的预测效果,水分含量、pH值的预测集相关系数(R p)分别为0.962 1、0.976 1,预测均方根误差(RMSEP)分别为0.012 9、0.145 2,表明模型具有较好的拟合度和预测性能。应用近红外光谱法进行红曲菌固态发酵过程的水分含量和pH值的快速检测可行,该方法为进一步实现其过程参数的在线检测及发酵条件优化提供了技术基础。     

近红外光谱法在红曲菌固态发酵过程参数检测中的应用

研究了近红外光谱技术快速检测红曲菌固态发酵过程参数水分含量和pH值的可行性。针对传统基于间隔策略波长选择方法忽略非线性因素的缺点,采用一种基于最小二乘支持向量机(Least squares support vector machines,LS-SVM)非线性模型的波长筛选算法：联合区间最小二乘支持向量机(Synergy interval least squares support vector machines,siLS-SVM),并将新算法与相关系数法、iPLS算法、siPLS算法对比。实验结果显示,联合siLS-SVM算法和LS-SVM模型取得了最好的预测效果,水分含量、pH值的预测集相关系数(Rp)分别为0.962 1、0.976 1,预测均方根误差(RMSEP)分别为0.012 9、0.145 2,表明模型具有较好的拟合度和预测性能。应用近红外光谱法进行红曲菌固态发酵过程的水分含量和pH值的快速检测可行,该方法为进一步实现其过程参数的在线检测及发酵条件优化提供了技术基础。     

生物质热反应机理与活化能确定方法Ⅰ.干燥段研究

干燥段是生物质热解的第一个过程.采用热分析仪研究了杉木木屑干燥段质量和热量的变化,推导了非等温干燥动力学模型,探讨了热质传输机理.结果表明,随着温度的升高,木屑含湿量迅速下降,80℃左右出现一个明显的失重峰;非等温干燥动力学Page模型能很好地模拟木屑干燥过程,木屑干燥活化能为12.6 kJ/mol;水分传输与热量传递...     

功能化的石墨烯和磁铁掺杂的还原氧化石墨烯对亚甲基蓝的吸附作用

用简单可行的方法合成了功能化的石墨烯(GNSPF6)和磁铁掺杂的还原氧化石墨烯(RGO-Fe3O4),并进一步研究了pH值、接触的时间和温度对它们吸附亚甲基蓝(MB)的影响.结果表明,随着pH值和温度的增加其吸附量也随之变大,从而说明该吸附过程是自发吸热的.因为GNSPF6的吸附过程只用了不到20min的时间,所以它的吸附是高效的.用经典的准一级反应、准二级反应和粒内扩散模型对其吸附过程进行动态分析,从结果可以发现,准二级动力学模型比准一级动力学模型更适用于描述吸附过程.采用传统的Langmuir,Freundlich和L-F吸附等温线模型来模拟分析数据,在20℃时,由Langmuir吸附等温线模型模拟分析得知GNSPF6和RGO-Fe3O4对MB的最大吸附量分别为374.4和118.4mg/g.     

桑葚醋发酵优化及提取物抗氧化能力分析

采用铁氰化钾(K3Fe(CN)6)还原法,以正交实验结果分别确定发酵时间、酵母菌含量、醋酸菌含量、发酵温度对桑葚人工发酵阶段的影响;实验表明,桑葚酒精发酵过程中总抗氧化能力最优的条件为:蔗糖含量14 g/100 mL,酵母菌含量5％,温度30℃;桑葚醋发酵过程中总抗氧化能力最优的条件为:酒精发酵时间为5 d,醋酸菌含量...     

Investigation on alpha-galactosidase production by Streptomyces griseoloalbus in a forcefully aerated packed-bed bioreactor operating in solid-state fermentation condition

Solid-state fermentation (SSF) was carried out for the production of extracellular alpha-galactosidase by Streptomyces griseoloalbus. Soybean flour was the best solid substrate for alpha-galactosidase production. Packed-bed bioreactor performed well in enhancing the enzyme yield and resulted in a highest yield of 197.2 +/- 0.02 U/gds with a forced aeration of 2 vvm, which was approximately twofold the yield obtained in flasks. The alpha-galactosidase production was growth-associated, and the highest enzyme yield was obtained after 96 h of incubation. It is significant that this is the first report on alpha-galactosidase production by a filamentous bacterium in SSF using packed-bed bioreactor.     

Modelling Growth and Bacteriocin Production by <Emphasis Type="Italic">Pediococcus acidilactici</Emphasis> PA003 as a Function of Temperature and pH Value

To investigate the effect of pH and temperature on the cell growth and bacteriocin production of Pediococcus acidilactici PA003, a lactic acid bacterium isolated from traditionally fermented cabbage, the kinetic behaviour of P. acidilactici PA003 was simulated in vitro during laboratory fermentations by making use of MRS broth. Firstly, primary models were developed for cell growth, glucose consumption, lactic acid and bacteriocin production for a given set of environmental conditions. Based on primary models, further study was undertaken to fit secondary models to describe the influence of temperature and pH on microbial behaviour. The models were validated successfully for all components. The results from the cell yield coefficient for lactic acid production reflected the homofermentative nature of P. acidilactici PA003. Both cell growth and bacteriocin production were very much influenced by changes in temperature and pH. The optimal condition for specific growth rate and biomass concentration was almost the same at pH 6.5 and 35 °C. At 35 °C and pH 6.1, the maximal bacteriocin activity was also achieved. The kinetic models provide useful tools for elucidating the mechanisms of temperature and pH on the kinetic behaviour of P. acidilactici PA003. The information obtained in this paper may be very useful for the selection of suitable starter cultures for a particular fermentation process and is a first step in the optimization of food fermentation processes and technology as well.     

Production of D-lactic acid by bacterial fermentation of rice starch

D-Lactic acid was synthesized by the fermentation of rice starch using microorganisms. Two species: Lactobacillus delbrueckii and Sporolactobacillus inulinus were found to be active in producing D-lactic acid of high optical purity after an intensive screening test for D-lactic acid bacteria using glucose as substrate. Rice powder used as the starch source was hydrolyzed with a combination of enzymes: alpha-amylase, beta-amylase, and pullulanase to obtain rice saccharificate consisting of maltose as the main component. Its average gross yield was 82.5%. Of the discovered D-lactic acid bacteria, only Lactobacillus delbrueckii could ferment both maltose and the rice saccharificate. After optimizing the fermentation of the rice saccharificate using this bacterium, pilot scale fermentation was conducted to convert the rice saccharificate into D-lactic acid with a D-content higher than 97.5% in a yield of 70%. With this yield, the total yield of D-lactic acid from brown rice was estimated to be 47%, which is almost equal to the L-lactic acid yield from corn. The efficient synthesis of D-lactic acid can open a way to the large scale application of high-melting poly(lactic acid) that is a stereocomplex of poly(L-lactide) and poly(D-lactide). Schematic representation of the production of D-lactic acid starting from brown rice as described here.     

Synthesis of PHB nanoparticles from optimized medium utilizing dairy industrial waste using Brevibacterium casei SRKP2: A green chemistry approach

Polyhydroxyalkanoates (PHAs) are natural, biodegradable polymers accumulated by bacteria under nutritional exhausted condition where carbon source is in excess. A gram positive bacterium (designated strain SRKP2) that potentially accumulated polyhydroxybutyrate (PHB) was isolated from dairy industrial waste. From its morphological and physiological properties and nucleotide sequence of its 16S rRNA, it was suggested that strain SRKP2 was similar to Brevibacterium casei. PHAs were synthesized from a medium containing dairy waste, yeast extract and sea water. The synthesized PHAs were characterized by FT-IR as Polyhydroxybutyrate (PHB). Response surface methodology was applied to optimize the production of PHB. From the optimized medium the yield of PHB was found to be 2.940 g/L. Here we report the direct use of dairy waste and sea water as potential sources for the production of PHB. Produced PHB was used to synthesize nanoparticles using solvent displacement technique.     

Effect of tributylphenyltetraethoxylate on enzyme production of Pleurotus ostreatus

The effect of the addition of the nonionic surfactant tributylphenyl-tetraethoxylate to culture media on pH and extracellular protein content, and on production of β-glucosidase, xylanase, laccase, and manganese-dependent and-independent peroxidases by the edible fungus Pleurotus ostreatus was determined. The relationship between fermentation parameters and concentration of surfactant was assessed by multiple linear regression analysis, and the similarities and differences among the fermentation parameters were elucidated by principal component analysis. Calculations proved that except for xylanase all other cultivation parameters were significantly influenced by the surfactant, with the effect higher at higher surfactant concentrations. Surfactant increased the production of β-glucosidase and inhibited laccase and manganese-dependent and-independent peroxidase activities.     

Enhanced Butanol Production Through Adding Organic Acids and Neutral Red by Newly Isolated Butanol-Tolerant Bacteria

As alternative microorganisms for butanol production with high butanol tolerant and productivity are in high demand, one excellent butanol-tolerant bacterium, S10, was isolated and identified as Clostridium acetobutylicum S10. In order to enhance the performance of butanol production, organic acids and neutral red were added during butanol fermentation. Synergistic effects were exhibited in the combinations of organic acids and neutral red to promote butanol production. Consequently, the optimal concentrations of combined acetate, butyrate, and neutral red were determined at sodium acetate 1.61 g/L, sodium butyrate 1.88 g/L, and neutral red 0.79 g/L, respectively, with the butanol yield of 6.09 g/L which was 20.89 % higher than that in control. These results indicated that combination of adding organic acid and neutral red is a potential effective measure to improve butanol production.     

Use of Different Extracts of Coffee Pulp for the Production of Bioethanol

Coffee is one of the most important agricultural products in Brazil. More than 50 % of the coffee fruit is not used for the production of commercial green coffee and is therefore discarded, usually ending up in the environment. The goal of this work was to select an efficient process for obtaining coffee pulp extract and to evaluate the use of this extract in bioethanol production. The effects of heat treatment and trituration on the yield and composition of the extract were investigated by measuring the amounts of reducing sugars, starch, pectin, and phenolic compounds. The extraction process was most efficient at room temperature using grinding followed by pressing. Five different fermentation media were tested: sugarcane juice or molasses diluted with water or with coffee pulp extract and a medium with only coffee pulp extract. Batch fermentations were carried out at 30 °C for 24 h, and samples were taken to obtain measurements of the total reducing sugars, cell count, and ethanol concentration. The addition of coffee pulp extract did not influence the fermentation or yeast viability, and it can thus be mixed with sugarcane juice or molasses for the production of bioethanol, with a yield of approximately 70 g/L.     

Production of xylitol byCandida mogii from rice straw hydrolysate

The influence of aeration level, initial pH, initial cell concentration, and fermentation time on the xylitol production from rice straw hemicellulose hydrolysate byCandida mogii was studied. A multifactorial experimental design was adopted to evaluate this influence. A statistical analysis of the results showed that the aeration level and the initial pH had significant effects on yield factor, volumetric productivity, and xylose consumption. For the latter, fermentation time was also a significant variable. Based on the response surface methodology, models for the range investigated were proposed. The maximum values for the yield factor (Y_p/s) and volumetric productivity (Q_p) were, respectively, 0.71 g/g and 0.46 g(Lh).