光合细菌生物膜的研究进展

光合细菌生物产氢技术能够将有机废水处理和氢气制备有效结合起来。光合细菌的产氢能力在形成生物膜后变强, 这有利于实现光合细菌的工业化应用。介绍了光合细菌生物膜的形成过程和对光合细菌生物膜形成的模拟研究, 综述了光照、流速、载体等对光合细菌生物膜的形成和产氢性能的影响。借鉴免疫学对生物膜的研究方法和技术, 并深入对光合细菌生物膜形成机理的全面认识, 提高光合细菌生物膜的性能, 是光合细菌生物膜研究的重要方向。     

嗜酸氧化亚铁硫杆菌生长动力学

在确定二价铁离子为A.f生长过程中惟一限制性底物条件下,通过考察初始亚铁离子浓度、初始pH值两种影响亚铁离子氧化代谢的主要因素来研究细菌的生长特性,得到以限制性底物亚铁离子浓度为表征的细菌生长曲线。利用基于Monod方程建立的细菌生长动力学方程模型,采用Matlab软件中的Gauss-Newton算法确定了在不同条件下细菌生长动力学参数,包括最大比生长速率μm、Monod常数K及Ro,推导出了不同条件下A.f对数期以底物Fe(Ⅱ)浓度为表征的生长动力学方程。     

初始底物浓度对序批式培养光合细菌产氢动力学影响

实验研究了初始底物浓度对序批式培养光合细菌生长、降解及产氢过程的影响,根据最大比生长速率实验数据拟合得到其关于初始底物浓度影响的关联式,并在建立的修正Monod模型基础上建立了光合细菌比生长速率、基质比消耗速率和比产氢速率关于底物初始浓度影响的数学模型,模型预测值与实验结果在光合细菌生长期和稳定期内得到较好吻合,反映了光合细菌生长、降解和产氢过程中受底物初始浓度限制性和抑制性影响的基本规律。分析发现光合细菌生长、降解基质和产氢过程中最适底物浓度为50 mmol/L,初始底物浓度低于或高于该浓度时,光合细菌生长、降解及产氢过程都受到限制性或抑制性影响,且抑制性影响较限制性影响效果更明显;底物比消耗速率受初始底物浓度影响较小。     

肉桂醛对阿萨希毛孢子菌临床分离株的生长及其生物膜形成的影响

目的研究中药单体肉桂醛是否对阿萨希毛孢子菌的生长及其生物膜形成有影响。方法选取临床分离菌株进行ITS基因序列分析及VITEK MS鉴定,通过培养建立体外生物膜模型。倍比稀释法测定1050 mg/L、525 mg/L、262.5 mg/L和131.25 mg/L浓度肉桂醛溶液对阿萨希毛孢子菌生长的抑制作用,银染法观察不同浓度肉桂醛对阿萨希毛孢子菌生物膜形成的影响。结果实验中各浓度的肉桂醛都能抑制阿萨希毛孢子菌的生长,延长生物膜的形成时间,且肉桂醛浓度越高,其作用效果越明显。当肉桂醛浓度达到1050 mg/L时,对阿萨希毛孢子菌生长的抑制效果最显著,该浓度下培养基孔内未见阿萨希毛孢子菌生长。银染法观察可见,此浓度下培养基内未形成生物膜,表明1050 mg/L浓度肉桂醛对阿萨希毛孢子菌生物膜的形成产生了明显的抑制作用。结论肉桂醛能够抑制阿萨希毛孢子菌生长及其生物膜形成。     

嗜酸氧化亚铁硫杆菌生长动力学方程的应用

基于Monod模型推导出了A．f的生长动力学方程模型,采用Gauss-Newton算法确定了在不同初始条件下细菌生长的动力学参数,即最大比生长速率‰、Monod常数K及R0。通过在不同初始条件下细菌生长特性的研究,得到了相应初始生长条件下以限制性底物亚铁离子浓度为表征的生长动力学方程,理论上揭示了动力学参数变化对细菌生长的影响规律,其中生长动力学方程的数值模拟与实验数据相吻合。     

利用光合菌发酵对玉米秸杆进行转化的研究*

系统研究了光合菌在氨法处理和非氨处理两种环境下,在厌氧、好氧、以及自然条件下对玉米秸秆的转化。通过发酵液中还原糖与蛋白质浓度的测定结果的比较、判断、优选出一种最适合条件下光合菌对玉米转化的途径。研究表明,在以氨化法处理的玉米秸秆为底物与光合菌的发酵实验中,发酵液中的还原糖和蛋白质的尝试都要比非氨法条件下玉米秸秆为底物与光合菌发酵实验中的发酵液中的不原糖和蛋白质的浓度高。实验结果证明了转化产生的还原糖、蛋白质都是光合菌能利用的营养成分,由此达到利用光合菌转化玉米秸秆的研究目的。     

非生物胁迫条件下施氏假单胞菌生物膜形成规律的研究

旨在系统研究非生物胁迫因素对固氮施氏假单胞菌A1501生物膜形成能力的影响,测定了不同NaCl浓度、pH值、温度等培养条件下A1501生长及其生物膜形成能力的变化规律。结果显示,上述3种环境因素均对A1501菌的生长及生物膜形成具有影响,且呈现出一定的规律性。NaCl浓度2 mmol/L、p H值6.8、温度30℃是A1501的最适生长条件,而在0.6 mol/L的NaCl、p H值6.0及温度40℃等胁迫条件下,A1501菌的生物膜形成量均达到最高,分别为最佳生长条件下的7.8、7.0和2.0倍。在测试的诸因素中,NaCl浓度对A1501生物膜形成影响最大。以上结果表明,生物膜的形成与菌体生长负相关,即高盐、弱酸、高温等条件不利于A1501的生长,但刺激了其生物膜的形成。     

大蒜素抗变异链球菌的致龋效果

目的研究大蒜素对口腔变异链球菌生长及其菌斑生物膜粘附的抑制作用。方法二倍稀释法梯度稀释测最小抑菌浓度(minimum inhibitory concentration,MIC),将MIC以上2个梯度浓度对应的培养物涂布于BHI培养基上进行次代培养获得最低杀菌浓度(minimum bactericidal concentration,MBC);酶标仪测A值观察不同浓度大蒜素抑菌效应;抑制产酸试验观察抑制细菌产酸效应;结晶紫法研究亚抑菌浓度提取物对变异链球菌粘附能力及生物膜总量的影响;采用激光共聚焦荧光显微镜(laser scanning confocal microscopy,LSCM)观察常态牙菌斑生物膜生长过程中及药物处理后牙菌斑生物膜中死菌和活菌的构成,研究其对牙菌斑生物膜结构和活性的影响。结果抑菌试验中,得到大蒜素MIC为12.8 mg/L,MBC为25.8 mg/L。MIC及亚抑菌浓度抑菌试验显示均有一定的抑菌性,抑制率为2.17%～67.12%,并且抑菌性与浓度梯度成正相关。产酸试验显示24 h内大蒜素明显抑制细菌产酸(P0.01),细菌粘附试验结果显示大蒜素在MIC时生物膜的生成速度最慢,生物膜的总量最低(P0.01)。共聚焦荧光显微镜可见大蒜素组随药物浓度增加,菌斑生物膜较薄,绿色的活菌及团块明显减少,抑制生物膜的生长。结论大蒜素对变异链球菌生长、产酸与粘附有一定抑制作用。     

细菌生物膜研究技术

细菌生物膜是细菌生长过程中为适应生存环境而在固体表面上生长的一种与游走态细胞相对应的存在形式。只要条件允许,绝大多数细菌都可以形成生物膜。一旦形成了生物膜细菌就具有极强的耐药性,在医疗、食品、工业、军事等诸多领域给人类社会带来了严重的危害,造成巨大的经济损失。因此,细菌生物膜已成为全球关注的重大难题,也是目前科学界研究的前沿和热点。本文结合细菌生物膜研究技术的最新进展,重点介绍了几种常用生物膜发生装置及检测量化技术,并对其原理及优缺点进行了讨论。     

不同营养条件下维罗纳气单胞菌菌毛表达与生物膜形成能力的比较

目的:检测不同培养基条件下(即不同营养条件下)维罗纳气单胞菌菌毛动力和生物膜生成能力(即致病能力)。方法:半固体培养基穿刺阳培养检测细菌动力,喉上皮细胞粘附实验检测生物膜形成能力,最后统计分析差异性。结果:BHIB培养基比LBA培养基中,野生型都比菌毛缺失的MSHB突变维罗纳气单胞菌有更高的动力和生物膜形成能力,但之间都无显著差异(P0.05)。结论:不同培养基基条件对菌毛动力有影响,而菌毛表达对生物膜致病性有一定关系。     

Prediction of substrate consumption rate, average biofilm density and active thickness for a thin spherical biofilm at pseudo-steady state

In this work, a new approach is proposed to evaluate substrate consumption rate, average biofilm density and active thickness of a spherical bioparticle in a completely mixed fluidized bed system. The substrate consumption rate and average biofilm density are predicted for a given biofilm surface substrate concentration and operational biofilm thickness. A diffusion and reaction model is developed with an effective diffusion coefficient that depends on the average biofilm density. This approach, a first in the literature, predicts the optimum average density of a biofilm to yield the maximum substrate consumption rate within the biofilm. A reasonable correlation was observed between the model prediction and experimental results for substrate consumption rate and average biofilm density for thin and fully active biofilms.     

Effects of flow rate and substrate concentration on the formation and H2 production of photosynthetic bacterial biofilms

Photosynthetic bacteria (PSB), Rhodopseudomonas palustris CQK 01, were immobilized on the surface of a thin glass slide in a lab-scale flat panel photobioreactor under different flow rates and substrate concentrations. The morphology, dry weight and thickness of the mature PSB biofilms were determined to reveal the relationship between biofilm formation and hydrogen production performance. The mature biofilm formed at a low flow rate and a high substrate concentration showed a looser structure, these structures of the mature biofilm then affected the H₂ production performance of the bioreactor during mature stage. The biofilm formed at a flow rate of 228 ml/h and a substrate concentration of 60 mmol/l exhibited the highest dry weight and optimally porous structure, which is beneficial not only for hydrogen removal from the biofilm but also glucose diffusion into the biofilm, thus significantly boosting the photo-hydrogen production performance.     

Enhancement of photo-hydrogen production in a biofilm photobioreactor using optical fiber with additional rough surface

In this study, a biofilm photobioreactor with optical fibers that have additional rough surface (OFBP-R) was developed and it was shown that additional rough surface greatly enhanced the biofilm formation and thus increased the cell concentration, leading to an improvement in the hydrogen production performance. The effects of operational conditions, including the influent substrate concentration, flow rate, temperature and influent medium pH, on the performance of OFBP-R were also investigated. The experimental results showed that the optimum operational conditions for hydrogen production were: the influent substrate concentration 60 mM, flow rate 30 mL/h, temperature 30 °C and influent medium pH 7. Under the optimal operation conditions discovered in this work, the OFBP-R yielded fairly good and stable long-term performance with hydrogen production rate of 1.75 mmol/L/h, light conversion efficiency of 9.3% and substrate degradation efficiency of 75%.     

Formation and growth of heterotrophic aerobic biofilms on small suspended particles in airlift reactors

In this article, the conditions for aerobic biofilm formation on suspended particles, the dynamics of biofilm formation, and the biomass production during the start-up of a Biofilm Airlift Suspension reactor (BAS reactor) have been studied. The dynamics of biofilm formation during start up in the biofilm airlift suspension reactor follows three consecutive stages: bare carrier, microcolonies or patchy biofilms on the carrier, and biofilms completely covering the carrier. The effect of hydraulic retention time and of substrate loading rate on the formation of biofilms were investigated. To obtain in a BAS reactor a high biomass concentration and predominantly continuous biofilms, which completely surround the carrier, the hydraulic retention time must be shorter than the inverse of the maximum growth rate of the suspended bacteria. At longer hydraulic retention times, a low amount of attached biomass can be present on the carrier material as patchy biofilms. During the start-up at short hydraulic retention times the bare carrier concentration decreases, the amount of biomass per biofilm particle remains constant, and biomass increase in the reactor is due to increasing numbers of biofilm particles. The substrate surface loading rate has effect only on the amount of biomass on the biofilm particle. A higher surface load leads to a thicker biofilm.A strong nonlinear increase of the concentration of attached biomass in time was observed. This can be explained by a decreased abrasion of the biofilm particles due to the decreasing concentration of bare carriers. The detachment rate per biofilm area during the start-up is independent of the substrate loading rate, but depends strongly upon the bare carrier concentration.The Pirt-maintenance concept is applicable to BAS reactors. Surplus biomass production is diminished at high biomass concentrations. The average maximal yield of biomass on substrate during the experiments presented in this article was 0.44 +/- 0.08 C-mol/C-mol, the maintenance value 0.019 +/- 0.012 C-mol/(C-mol h). The lowest actual biomass yield measured in this study was 0.15 C-mol/C-mol. (c) 1994 John Wiley & Sons, Inc.     

Impact of flow velocity on the dynamic behaviour of biofilm bacteria

Abstract

The impact of flow velocity (FV) on the growth dynamics of biofilms and bulk water heterotrophic plate count (HPC) bacteria in drinking water distribution systems was quantified and modeled by combining a logistic growth model with mass balance equations. The dynamic variations in the specific growth and release rates of biofilm bacteria were also quantified. The experimental results showed that the maximum biofilm biomass did not change when flow velocity was increased from 20 to 40 cm s^?1, but was significantly affected when flow velocity was further increased to 60 cm s^?1. Although the concentration of biofilm bacteria was substantially reduced by the higher shear stress, the concentration of bacteria in the bulk fluid was slightly increased. From this it is estimated that the specific growth rate and specific release rate of biofilm bacteria had doubled. The specific release (detachment) rate was dependent on the specific growth rate of the biofilm bacteria.     

Film analysis of activated sludge microbial discs by the Taguchi method and grey relational analysis

A biofilm model with substrate inhibition is proposed for the activated sludge growing discs of rotating biological contactor (RBC); this model is different from the steady-state biofilm model based on the Monod assumption. Both deep and shallow types of biofilms are examined and discussed. The biofilm models based on both Monod and substrate inhibition (Haldane) assumptions are compared. In addition, the relationships between substrate utilization rate, biofilm thickness, and liquid phase substrate concentration are discussed. The influence order of the factors that affect the biofilm thickness is studied and discussed by combining the Taguchi method and grey relational analysis. In this work, a Taguchi orthogonal table is used to construct the series that is needed for grey relational analysis to determine the influence priority of the four parameters S _B , kX _f , K _s, and K _i .     

Biofilm development in a membrane-aerated biofilm reactor: effect of intra-membrane oxygen pressure on performance

The effect on intra-membrane oxygen pressure at a constant carbon substrate loading rate on the development of biofilms of Vibrio natrigens in a membrane aerated biofilm reactor (MABR) was investigated experimentally and by mathematical modelling. A recently reported technique (Zhang et al., 1998. Biotechnol. Bioeng. 59: 80-89) for the in situ measurement of the substrate diffusion coefficients in a growing biofilm and the mass transfer coefficients in the boundary layer at the biofilm liquid interface was used. This aided the study of the effect of the heterogeneous biofilm structure and also improved the reliability of the model predictions. The different intra-membrane oxygen pressures used, 12.5, 25 and 50 kPa, with acetate as the carbon substrate, showed a marked effect on the initial biofilm growth rate, on acetate removal rate, particularly in thick biofilms and on biofilm structure. The model predicted the substrate limitation regimes, the location of the active biomass layer within the biofilms and the trends in oxygen uptake rate through the membrane into the biofilms. During the development of the biofilms, the biofilm thickness and the intra-membrane oxygen pressure were found to be the most important parameters influencing the MABR performance while the effect of biofilm structure was less marked.     

Surface-templated fibril growth of peptide fragments from the shaft domain of the adenovirus fibre protein

Here we present a study of five analogues of a fragment from the shaft domain of the adenovirus fibre protein that readily form fibrils under a range of conditions. Using atomic force microscopy the fibrillisation of these peptides at the liquid/solid interface utilizing ordered crystalline substrates has been investigated. Our results demonstrate that the assembly pathway at the liquid/solid interface enables only the formation of truncated fibrillar structures, which align along the substrate's underlying atomic lattice during growth. Furthermore, that the concentration and volume of solution applied can be used to directly control the density of fibrillar coverage at the surface.     

An analysis of a trickle-bed bioreactor: carbon disulfide removal

An analysis of the local processes occurring in a trickle-bed bioreactor (TBB) with a first-order bioreaction shows that the identification of the TBB operating regime requires knowledge of the substrate concentration in the liquid phase. If the substrate liquid concentration is close to 0, the rate-controlling step is mass transfer at the gas-liquid interface; when it is close to the value in equilibrium with the gas phase, the controlling step is the phenomena occurring in the biofilm. CS2 removal rate data obtained in a TBB with a Thiobacilii consortia biofilm are analyzed to obtain the mass transfer and kinetic parameters, and to show that the bioreactor operates in a regime mainly controlled by mass transfer. A TBB model with two experimentally determined parameters is developed and used to show how the bioreactor size depends on the rate-limiting step, the absorption factor, the substrate fractional conversion, and on the gas and liquid contact pattern. Under certain conditions, the TBB size is independent of the flowing phases' contact pattern. The model effectively describes substrate gas and liquid concentration data for mass transfer and biodegradation rate controlled processes.     

Substrate utilization and mass transfer in an autotrophic biofilm system: Experimental results and numerical simulation

An autotrophic biofilm has been investigated for over 10 months in a biofilm tube reactor. The objective of this investigation was the verification and improvement of a biofilm model. The use of a Clark-type oxygen microelectrode in situ allowed the determination of the substrate flux in the biofilm. Also, the population dynamics of the autotrophic bacteria could be evaluated by varying the substrate conditions. Simulation of the experimental results showed that the liquid phase of the biofilm decreased with biofilm depth. This could be described by a logistic function. The density of the inert volume fraction was found to be higher than that of the viable bacteria. This was verified in a nonsubstrate phase of 5 weeks. Growth and decay of the autotrophic bacteria could be described by the growth, endogenous respiration, and death processes. Mass transfer coefficients at the bulk/biofilm interface were evaluated. They were found to be one order of magnitude higher than those known from hydrodynamics in tubes without a biofilm. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 53: 363-371, 1997.