Microbial community in methanogenic packed-bed reactor successfully operating at short hydraulic retention time

The microbial community in a thermophilic anaerobic packed-bed reactor, which had been successfully operated to convert acetic and butyric acids to methane at a short hydraulic retention time (from 24 h to 1.9 h), was investigated. Archaea closely related to known methanogens were detected by 16S rRNA gene analyses of the effluents, together with diverse types of unidentified bacteria.     

l-Arabinose production from sugar beet arabinan by immobilized endo- and exo-arabinanases from Caldicellulosiruptor saccharolyticus in a packed-bed reactor

The immobilized endo- and exo-arabinanases from Caldicellulosiruptor saccharolyticus produced continuously an average of 16.5 gl(-1)l-arabinose from 20 gl(-1) sugar beet arabinan at pH 5.0 and 75°C for 216 h, with a productivity of 9.9 gl(-1)h(-1) and a conversion yield of 83%.     

基于模糊分散控制的双层搅拌微波反应釜混料均匀性自适应研究

以双层搅拌结构微波反应釜的混合搅拌时间与混合搅拌次数为关联特征量,采用模糊PID控制方法进行微波反应釜的物料双层搅拌结构自适应控制,以玻璃珠和氧化铝珠作为物料混合搅拌介质,进行双层搅拌的误差反馈调节和自适应控制,建立双层搅拌结构微波反应釜的物料混合均匀控制律,通过物料混合均匀控制的优化控制函数的求取,实现物料混合均匀等。仿真结果表明,采用该方法进行双层搅拌结构微波反应釜的物料混合控制均匀性较好,物料混合均匀控制双层搅拌的稳定性较好。     

Production and oxidative stability of a human milk fat substitute produced from lard by enzyme technology in a pilot packed-bed reactor

Residence time and time of production were investigated during the enzymatic production of a specific structured lipid/human milk fat substitute (SL-HMFS), on a kg scale, made from lard and soybean oil fatty acids, using a packed-bed reactor and short path distillation. There were no effects of residence time or time of production on C18:2 and C18:3 incorporation or on acyl migration in the sn-2 position. In addition, the SL-HMFS was compared to commercial human milk fat substitute (HMFS) regarding fatty acid composition, content of antioxidants and oxidative stability. Fats were stored at 60 °C for four days and the oxidative stability evaluated by analysis of peroxide value (PV) and volatile secondary oxidation products. SL-HMFS had a lower oxidative stability than did commercial HMFS products or lard, probably due to a lower level of tocopherol in SL-HMFS.     

Enzymatic synthesis of lard-based ascorbyl esters in a packed-bed reactor: Optimization by response surface methodology and evaluation of antioxidant properties

An optimal continuous production of lard-based ascorbyl esters (LBAEs) by transesterification of lard with l-ascorbic acid in a packed bed reactor (PBR) was developed using immobilized lipase (Novozym 435) as a catalyst in a tert-amyl alcohol solvent system. Response surface methodology (RSM) and central composite design (CCD) were employed to evaluate the effects of substrate flow rate, reaction temperature and substrate molar concentration ratio on the molar conversion of LBAEs. The optimum conditions were as follows: substrate flow rate 1.07 ml/min, reaction temperature 56.44 °C, and substrate molar concentration ratio 2.24:1. The optimum predicted LBAEs yield was 50.83% and the actual value was 50.50%. The above results shows that the RSM study based on CCD is adaptable for LBAEs yield studied for the current transesterification system. The antioxidant activities of LBAEs has also been studied. LBAEs represented positive antioxidant potential on superoxide anion radical and hydroxyl radicals and satisfactory antioxidant activity in lard and soybean oil. The results suggest that LBAEs has the potential to serve as natural antioxidant in food system.     

填充床固态发酵生物反应器模拟研究进展

数学模型是固态发酵生物反应器设计、优化和操作的重要工具,它不仅可以指导SSF过程生物反应器的设计和操作,而且可以深入分析发酵系统内的各种现象从而控制整个发酵过程。文章分析近几年固态发酵填充床生物反应器的拟均相假设模拟模型、非均相假设模拟模型和间歇混合填充床生物反应器模拟模型,对模拟结果进行讨论,深入分析如何用数学方法描述SSF系统的传热传质模型。在分析填充床固态发酵底物床层的系统组成及其性质的基础上,提出利用多孔介质体积平均理论研究SSF系统传热传质过程的可能性。     

Kinetics of inulinase production by solid-state fermentation in a packed-bed bioreactor

In this work the cell growth and inulinase production by Kluyveromyces marxianus NRRL Y-7571 were investigated in a packed-bed bioreactor. For this purpose, seven experimental runs were carried out in order to verify the influence of the inlet air temperature and volumetric air flow rate on the process dynamics. The results showed that the manipulated variables affected significantly the process performance. The best condition for enzyme production was an inlet air temperature and volumetric flow rate of 30 °C and 3 m³ h⁻¹, respectively, reaching an activity of around 463 U gds⁻¹. The results obtained here can be useful in the scale-up and optimisation of packed-bed bioreactors configuration for inulinase production.     

Effect of ammonium addition on methanogenic community in a fluidized bed anaerobic digestion

After immobilization of anaerobes on carbon felt in a fluidized-bed anaerobic digester at an ammonium concentration of 500 mg N/l, the results of real-time PCR analysis indicated that the cell densities of the immobilized methanogens and bacteria increased compared with those of the free-living methanogens and bacteria in the original anaerobically digested sewage sludge, respectively. The results of the clone analysis of the original sludge suggested that the major methanogens were Methanosaeta sp. and the members of the order Methanomicrobiales, and that after immobilization, these were changed to Methanobacterium and Methanosarcina sp. The results of real-time PCR analysis also showed that the ratio of the Methanosaeta sp. in the methanogenic archaea decreased from 58.2% to 0.3% after the immobilization. Methane production decreased at ammonium concentrations of greater than 6000 mg N/l. The results of real-time PCR analysis indicated that the cell density of the immobilized archaea decreased at ammonium concentrations of greater than 3000 mg N/l. On the other hand, the cell density of the immobilized bacteria did not decrease at an ammonium concentration of 6000 mg N/l, but decreased at that of 9000 mg N/l. The major methanogenic clones immobilized on the carbon felt at an ammonium concentration of 3000 or 6000 mg N/l were Methanobacterium sp. The present results indicated that methanogens were relatively more sensitive to ammonium than bacteria.     

浓香型白酒窖泥古菌群落结构研究及其系统发育学分析

本试验分别提取30、100和200年窖龄窖泥样品总DNA,采用PCR-DGGE和16S rDNA测序技术探索浓香型白酒不同窖龄窖泥古菌群落演替规律,结果表明:不同窖龄窖泥的古菌DGGE图谱均出现14~17条较清晰的条带,其中第4、7、11号条带在所有样品中均有检出,且优势度较高,均在4%以上;不同窖龄窖泥的古菌群落多样性指数都在1.91~2.29之间,且随窖龄的增加而呈现上升趋势;不同窖龄窖泥的古菌相似性指数在0.43~0.61之间,30年与100年窖泥古菌群落相似性指数达到了0.61且聚为一类,与200年古菌群落相似性指数相比较却分为两类。PCR-DGGE图谱优势条带割胶测序结果显示:他们分属于产甲烷古菌(Methanogenic archaeon)、甲烷袋状菌属(Methanoculleus sp)、甲烷八叠球菌属(Methanosarcinales archaeon)、瘤胃古菌属(Rumen archaeon)四个类群。本研究结果对浓香型白酒窖泥古菌群落有了一定的认识。     

Biodegradation of short-chain n-alkanes in oil sands tailings under methanogenic conditions

The biodegradation of a mixture of low molecular weight n-alkanes (C6, C7, C8, and C10) was assessed under methanogenic conditions using mature fine tailings (MFT) produced by the oil sands industry in Alberta, Canada. Microorganisms present in the MFT mineralized the added n-alkane mixture, producing 16.2 (+/- 0.3) or 20.5 (+/- 0.1) mmol of methane in the headspace of microcosms spiked with 0.2% or 0.5% w/v n-alkanes, respectively, during 29 weeks of incubation. The spiked n-alkanes biodegraded in the sequence C10 > C8 > C7 > C6. Degradation of 100% C10, 97% C8, 74% C7, and 44% C6 occurred in a mixture of n-alkanes in the MFT spiked at 0.2% after 25 weeks of incubation. The same pattern of biodegradation was also observed in the MFT spiked with 0.5% n-alkanes. Stoichiometric calculations confirmed the mineralization of the degraded n-alkanes to methane. This study showed that the short-chain n-alkanes, which comprise a significant portion of the unrecovered naphtha used in bitumen extraction and released into the settling basins, can be biodegraded into methane. These findings may influence decisions regarding extraction processes and long-term management of MFT, and they suggest that intrinsic, methanogenic metabolism of these n-alkanes may occur in other anoxic environments.     

Anaerobic treatment performance and microbial population of thermophilic upflow anaerobic filter reactor treating awamori distillery wastewater

Distillery wastewater from awamori making was anaerobically treated for one year using thermophilic upflow anaerobic filter (UAF) reactors packed with pyridinium group-containing nonwoven fabric material. The microbial structure and spatial distribution of microorganisms on the support material were characterized using molecular biological methods. The reactor steadily achieved a high TOC loading rate of 18 g/l/d with approximately 80% TOC removal efficiency when non-diluted wastewater was fed. The maximum TOC loading rate increased to 36 g/l/d when treating thrice-diluted wastewater. However, the TOC removal efficiency and gas evolution rate decreased compared with that when non-diluted wastewater was used. Methanogens closely related to Methanosarcina thermophila and Methanoculleus bourgensis and bacteria in the phyla Firmicutes and Bacteroidetes were predominant methanogens and bacteria in the thermophilic UFA reactor, as indicated by 16S rRNA gene clone analysis. Fluorescence in situ hybridization (FISH) results showed that a large quantity of bacterial cells adhered throughout the whole support, and Methanosarcina-like methanogens existed mainly in the relative outside region while Methanoculleus cells were located in the relative inner part of the support. The support material used proved to be an excellent carrier for microorganisms, and a UAF reactor using this kind of support can be used for high-rate treatment of awamori/shochu distillery wastewater.     

Gaseous hexane biodegradation by Fusarium solani in two liquid phase packed-bed and stirred-tank bioreactors

Biofiltration of hydrophobic volatile pollutants is intrinsically limited by poor transfer of the pollutants from the gaseous to the liquid biotic phase, where biodegradation occurs. This study was conducted to evaluate the potential of silicone oil for enhancing the transport and subsequent biodegradation of hexane by the fungus Fusarium solani in various bioreactor configurations. Silicone oil was first selected among various solvents for its biocompatibility, nonbiodegradability, and good partitioning properties toward hexane. In batch tests, the use of silicone oil improved hexane specific biodegradation by approximately 60%. Subsequent biodegradation experiments were conducted in stirred-tank (1.5 L) and packed-bed (2.5 L) bioreactors fed with a constant gaseous hexane load of 180 g x m(-3)(reactor) x h(-1) and operated for 12 and 40 days, respectively. In the stirred reactors, the maximum hexane elimination capacity (EC) increased from 50 g x m(-3)(reactor) x h(-1) (removal efficiency, RE of 28%) in the control not supplied with silicone oil to 120 g x m(-3)(reactor) x h(-1) in the biphasic system (67% RE). In the packed-bed bioreactors, the maximum EC ranged from 110 (50% RE) to 180 g x m(-3)(reactor) x h(-1) (> 90% RE) in the control and two-liquid-phase systems, respectively. These results represent, to the best of our knowledge, the first reported case of fungi use in a two-liquid-phase bioreactor and the highest hexane removal capacities so far reported in biofilters.     

Dynamic seeding and perfusion culture of hepatocytes with galactosylated vegetable sponge in packed-bed bioreactor

A galactose moiety was introduced into the fiber surface of a vegetable sponge by the covalent binding of lactobionic acid. The galactosylated sponge was used as scaffold for the culture of rat hepatocytes in a packed-bed bioreactor. Hepatocytes could be dynamically seeded into and uniformly distributed throughout the scaffold, and the immobilized cells maintained high albumin and urea production rates during long-term perfusion culture. The hepatocytes showed an increasing albumin production rate from 49 to 109 microg/10(6) cells/d over the 7-d culture.     

Influence of Ni and Co on methanogenic activity and the amounts of coenzymes involved in methanogenesis

The requirement of Ni²⁺ and Co²⁺ addition on methanogenic activity and the coenzymes involved in methanogenesis were investigated in anaerobic continuous cultivation with synthetic wastewater using acetate as the sole carbon source. Addition of Ni²⁺ and Co²⁺ to the synthetic wastewater drastically increased the maximum dilution rate of the cultivation. The concentrations of coenzymes F₄₃₀ and corrinoids in the biomass increased to 0.62 μmol-Ni/g-VSS and 0.67 μmol-Co/g-VSS, respectively with the increase of the dilution rate. Methanogenic activity of the culture broth also increased with an increase of dilution rate. However, without addition of Ni²⁺ and Co²⁺, F₄₃₀ and corrinoids were not detected in the biomass and methanogenic activity was only a trace level at a dilution rate of 0.025 d⁻¹. When the amounts of Ni²⁺ and Co²⁺ added at a dilution rate of 0.6 d⁻¹ were lowered in steps, the concentrations of F₄₃₀ and corrinoids in the biomass and methanogenic activity decreased with decreasing amounts of Ni²⁺ and Co²⁺ added. These results suggest that Ni²⁺ and Co²⁺ were required for the methane-producing reactions via increases of coenzymes F₄₃₀ and corrinoids.     

Influence of growth phase on bacterial deposition: interaction mechanisms in packed-bed column and radial stagnation point flow systems

The influence of bacterial growth stage on cell deposition kinetics has been examined using a mutant of Escherichia coli K12. Two experimental techniques--a packed-bed column and a radial stagnation point flow (RSPF) system--were employed to determine bacterial deposition rates onto quartz surfaces over a wide range of solution ionic strengths. Stationary-phase cells were found to be more adhesive than mid-exponential phase cells in both experimental systems. The divergence in deposition behavior was notably more pronounced in the RSPF than in the packed-bed system. For instance, in the RSPF system, the deposition rate of the stationary-phase cells at 0.03 M ionic strength was 14 times greater than that of the mid-exponential cells. The divergence in the packed-bed system was most significant at 0.01 M, where the deposition rate for the stationary-phase cells was nearly 4 times greater than for the mid-exponential cells. To explain the observed adhesion behavior, the stationary and mid-exponential bacterial cells were characterized for their size, surface charge density, electrophoretic mobility, viability, and hydrophobicity. On the basis of this analysis, it is suggested that the stationary cells have a more heterogeneous distribution of charged functional groups on the bacterial surface than the mid-exponential cells, which results in higher deposition kinetics. Furthermore, because the RSPF system enumerates only bacterial cells retained in primary minima, whereas the packed column captures mostly cells deposited in secondary minima, the difference in the stationary and mid-exponential cell deposition kinetics is much more pronounced in the RSPF system.     

聚焦原料皮

无论对于BLC的研究项目还是商务活动而言 ,有关原料皮的工作一直扮演着重要的角色 ,而且 ,这方面的工作也越来越受到政府的特别关注。现今 ,我们一直研究的是有关畜牧业对皮革质量、数量和肉食安全卫生的影响 ,并研究在屠宰场受到污染的动物皮与公共健康之间的密切关系。2 0 0 0年 4月由UK的食品标准机构(FSA)发起 ,由环境、食品和农业事务(DEFRA)部门共同协作提出 ,食品安全卫生的改善是各行业共同努力的中心问题。对于皮革行业来讲 ,以安全为中心的条款进一步推动了清洁饲养的发展 ,更加强调了肉食安全研究并在行业内普及的重要性 ,这项工作的深入进行 ,预示着皮革质量的长期稳定和持续性改善。本论文的中心是肉食安全问题 ,同时探讨不洁家畜对皮革质量的影响以及FSA将采取怎样的行动来实现即定目标     

Effect of dilution rate on structure of a mesophilic acetate-degrading methanogenic community during continuous cultivation

The community structures of two mesophilic acetate-degrading methanogenic consortia enriched at dilution rates of 0.025 and 0.6 d(-1) were analyzed by fluorescence in situ hybridization (FISH) and phylogenetic analyses based on 16S rDNA clonal sequences and quantitative real-time polymerase chain reaction (PCR). FISH experiments with archaeal and bacterial domain-specific probes showed that archaeal cells were predominant and only a small number of bacterial cells were detected at both dilution rates. In the domain Archaea, the number of cells closely related to Methanosarcina barkeri was shown to be greater at the high dilution rate using FISH with species-specific probes. Taxonomic analyses based on rDNA clonal sequences obtained at the low and high dilution rates showed that 43% of 100 clones and 72% of 92 clones, respectively, were affiliated with the domain Archaea and the remainders at each dilution rate were affiliated with the domain Bacteria. Within the domain Archaea, all rDNA clones at both dilution rates were affiliated with the genera Methanosaeta or Methanosarcina of the aceticlastic methanogens. Within the domain Bacteria, the rDNA clones obtained at the low dilution rate were affiliated with four phyla, Firmicutes (36%), Bacteroidetes (9%), Chloroflexi (6%) and candidate division OP12 (5%). The rDNA clones obtained at the high dilution rate were affiliated with four phyla, Firmicutes (16%), Bacteroidetes (8%), Proteobacteria (1%) and candidate division OP12 (3%). Real-time quantitative PCR experiments showed that the number of rDNA sequences affiliated with the genus Methanosarcina was greater at the high dilution rate. In addition, a significant number of rDNA sequences affiliated with the genus Methanoculleus were detected only at the low dilution rate. Detection of a hydrogenotrophic methanogen at the low dilution rate suggests that the syntrophic acetate oxidation by hydrogenotrophic methanogens and acetate-oxidizing bacteria could occur at the low dilution rate.     

Effect of temperature on microbial community of a glucose-degrading methanogenic consortium under hyperthermophilic chemostat cultivation

We continuously fed an anaerobic chemostat with synthetic wastewater containing glucose as the sole source of carbon and energy to study the effects of temperature on the microbial community under hyperthermophilic (65-80 degrees C) conditions. Methane was produced normally up to 77.5 degrees C at a dilution rate of 0.025 d(-1). However, the concentration of microorganisms and the rate of gas production decreased with increasing operation temperature. The microbial community in the chemostat at various temperatures was analyzed based on the 16S rRNA gene using molecular biological techniques including clone library analysis and denaturing gradient gel electrophoresis (DGGE). Aceticlastic methanogens related to Methanosarcina thermophila were detected at 65 degrees C and hydrogenotrophilic methanogens related to Methanothermobacter thermautotrophicus were the dominant methanogens between 70 degrees C to 77.5 degrees C. Bacteria related to Clostridium stercorarium and Thermoanaerobacter subterraneus comprised the dominant glucose-fermenting bacteria at temperatures of 65 degrees C and above, respectively. Bacteria related to Thermacetogenium phaeum and to Tepidiphilus margaritifer and Petrobacter succinatimandens were the dominant acetate-oxidizing bacteria at 70 degrees C and at 75-77.5 degrees C, respectively. The results suggested that, at temperatures of 70 degrees C and above, methane production via the aceticlastic pathway was negligible and indirect methanogenesis from acetate was dominant. Since acetate oxidation is a rate limiting step and a higher temperature favors the hydrolysis and acid formation, a two stage fermentation process, acidogenic and methanogenic fermentation stages operated under different temperatures, should be more suitable for the thermophilic anaerobic treatment at temperatures above 65 degrees C.