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Biochemical Engineering Journal (v.37, #1)
Antagonistic fungi, Trichoderma spp.: Panoply of biological control by Mausam Verma; Satinder K. Brar; R.D. Tyagi; R.Y. Surampalli; J.R. Valéro (pp. 1-20).
Trichoderma spp. have been widely used as antagonistic fungal agents against several pests as well as plant growth enhancers. Faster metabolic rates, anti-microbial metabolites, and physiological conformation are key factors which chiefly contribute to antagonism of these fungi. Mycoparasitism, spatial and nutrient competition, antibiosis by enzymes and secondary metabolites, and induction of plant defence system are typical biocontrol actions of these fungi. On the other hand, Trichoderma spp. have also been used in a wide range of commercial enzyme productions, namely, cellulases, hemicellulases, proteases, and β-1,3-glucanase. Information on the classification of the genus, Trichoderma, mechanisms of antagonism and role in plant growth promotion has been well documented. However, fast paced current research in this field should be carefully updated for the fool-proof commercialization of the fungi. The aim of this review is to sum up the BCA activity potential of these fungi and to shed light on commercial production processes. In this regard, this review focuses on Trichoderma spp. discussing different aspects—pest control, growth promotion, bioremediation, production processes and market values. Nevertheless, more research and review of the information regarding these biocontrol agents are needed to exploit their actual potential, which is the salient objective of this review.
Keywords: Antagonism; Biocontrol agents; Microbial propagules; Trichoderma; spp.; Wastewater; Wastewater sludge
Effects of using light-emitting diodes on the cultivation of Spirulina platensis by Chih-Yu Wang; Chun-Chong Fu; Yung-Chuan Liu (pp. 21-25).
Various light-emitting diodes (LEDs) with different light wavelengths and illumination intensities were employed to explore the effects of light source on photoautotrophic cultivation of Spirulina platensis. From the experimental results, red LED exhibited the highest specific growth rate of 0.40 (day−1) under the condition of 3000μmolm−2s−1. Blue LED showed the least efficiency in the conversion of photon to biomass. Hence, a modified Monod model was proposed to fit the specific growth rates of S. platensis from different light sources. The light intensity threshold for minimum photoautotrophic growth was also determined. In comparing the economic efficiency of energy to biomass, the use of red LED gave the most effective performance for the photoautotrophic cultivation.
Keywords: Light-emitting diodes; Spirulina platensis; Monod model; Economic efficiency; Photoautotrophic cultivation
Effective induction of phytase in Pichia pastoris fed-batch culture using an ANN pattern recognition model-based on-line adaptive control strategy by Hu Jin; Zhiyong Zheng; Minjie Gao; Zuoying Duan; Zhongping Shi; Zhengxiang Wang; Jian Jin (pp. 26-33).
An on-line adaptive substrate feeding control system based on DO/pH measurements and artificial neural network pattern recognition (ANNPR) model for fed-batch cultivation processes proposed previously was successfully applied for the phytase production with recombinant Pichia pastoris. The control strategy could effectively improve the fermentation performance for both cultivation and induction phases. With the standard ANNPR model-based control strategy, the cultivation time before starting the methanol induction could be shortened for about 30%. By adequately increasing the feeding rate iterative step size of the ANNPR-based control during induction phase, methanol concentration could be automatically controlled within an optimal range, leading to an approximate three-fold stable increase in phytase activity compared with those obtained by the traditional DO-Stat method and the on-line methanol electrode-based on–off control strategy. The effectiveness, universal ability, as well as the operational simplicity of the proposed control system has been further verified in the recombinant P. pastoris fed-batch culture process.
Keywords: Fed-batch culture; On-line adaptive control; Pattern recognition; Phytase production; Pichia pastoris
Immobilization studies and biochemical properties of free and immobilized Rhizopus oryzae lipase onto CaCO3: A comparative study by Hanen Ghamgui; Nabil Miled; Maha Karra-chaâbouni; Youssef Gargouri (pp. 34-41).
Lipase from Rhizopus oryzae (ROL) was immobilized by physical adsorption onto CaCO3. The immobilization yield was more than 95% during 30min and corresponds to the loading of 2570IU/g support. The optimum temperature for both free and immobilized lipase activities was 37°C. After 24h of incubation at 50°C, the immobilized ROL maintained 67% of its initial activity, while the free enzyme was completely inactivated. Therefore, the immobilization seems to improve highly the lipase thermal stability. Besides, the immobilized lipase showed a higher stability than free lipase when stored at 4°C. The kinetics of the olive oil hydrolysis by the immobilized lipase showed that the hydrolysis rate reached the maximum within 15min of incubation with the substrate. The hydrolytic activity of the immobilized lipase on olive oil used as substrate was higher than that of the free lipase form, as shown by a higher amount of released free oleic acid. We studied the ethyl oleate ester (biofuel) synthesis by immobilized and free ROL. The conversion yield of this ester was also found to be higher with the immobilized lipase than with the free lipase form (83% versus 6%). Furthermore, electron microscopy allowed us to observe that the morphology of the surface of CaCO3 after the adsorption of ROL showed a large contact area of multipoint attachment with the enzyme.
Keywords: Abbreviations; ROL; Rhizopus oryzae; lipase; MO; mono-olein; DO; diolein; OA; oleic acid; TO; triolein; TLC; thin layer chromatography; IU; international unit; TU; total unitsCaCO; 3; Rhizopus oryzae; lipase; Immobilization; Hydrolysis; Synthesis; Electron microscopy
A pilot-study on treatment of a waste gas containing butyl acetate, n-butyl alcohol and phenylacetic acid from pharmaceutical factory by bio-trickling filter by Qun Hui Wang; Lanhe Zhang; Shulei Tian; Paul Ta-Chin Sun; Weimin Xie (pp. 42-48).
A bio-trickling filter packed with fibrous balls, ZX02, packing material was tested to treat a mixed waste gas containing butyl acetate (BA), n-butyl alcohol ( n-BA) and phenylacetic acid (PA), which were discharged from penicillin workshop in a pharmaceutical factory. In order to investigate the effect of various factors such as inlet loading and spray water flow rate on the removal rate of these three volatile pollutants, a field experiment was carried out continuously for more than 3 months using a pilot bio-trickling filter and effluent from a wastewater treatment plant was used as spray water during the pilot experiment. The removal rates of BA, n-BA and PA was 95%, 92% and nearly 100%, when their inlet concentration was lower than 2200, 2400 and 370mgm−3, respectively. To maintain 90% removal of BA, n-BA and PA, acceptable maximum inlet loadings cannot exceed 373.4, 317.2 and 209.5gm−3h−1, respectively. The effluent from the secondary sedimentation tank of the pharmaceutical wastewater treatment plant can be used as spray water, and its optimal flow rate was determined to be 9.5–10.5Lh−1. The bio-trickling filter had significant ability to resist shock of high inlet loading while maintaining low resistances to air flow. Therefore, it can be operated for long-term without frequent backwashing.
Keywords: Bio-trickling filter; Butyl acetate; n; -Butyl alcohol; Phenylacetic acid; Volatile organic compounds
Nitrification of landfill leachate using immobilized nitrifying bacteria at low temperatures by Kazuichi Isaka; Sachiko Yoshie; Tatsuo Sumino; Yuhei Inamori; Satoshi Tsuneda (pp. 49-55).
A technology to achieve stable and high rates of nitrification of landfill leachate at low temperatures has been desired. Nitrifying bacteria entrapped in a polyethylene glycol (PEG) gel carrier produced high nitrification rates of 0.71kgN/m3/day at 10°C for more than 1 year. As a characteristic of nitrification, ammonium nitrogen at 16–35mg/L remained in effluent water irrespective of nitrogen load and nitrite accumulation was observed. Batch experiments clearly showed that the relationship between ammonium concentration and ammonium removal rate followed a Monod-type equation. It was also revealed that ammonium-oxidizing bacteria cultivated in a gel carrier had a low affinity for ammonium, leading to incomplete nitrification. Moreover, it was suggested that the remaining ammonium in the reactor produced free ammonium, which inhibited the activities of nitrite-oxidizing bacteria. Thus, only nitritation was observed. Molecular biological methods, such as denaturing gradient gel electrophoresis (DGGE) and fluorescence in situ hybridization (FISH), revealed that Nitrosomonas sp. was the dominant ammonium-oxidizing bacteria in the gel carrier at low temperature.
Keywords: Aerobic processes; Bioreactor; Immobilization; Wastewater treatment; Nitrification; Leachate
Optimization of distinction between viable and dead cells by fluorescent staining method and its application to bacterial consortia by Kazuhiko Miyanaga; Suguru Takano; Yuki Morono; Katsutoshi Hori; Hajime Unno; Yasunori Tanji (pp. 56-61).
A technique to distinguish viable and dead cells has long been considered necessary in various fields such as sterilization, toxicity assessment, sanitary evaluation and so on. A bacterial staining method using fluorescent dye is a popular tool, although the weakness of fluorescence intensity and its fading over time constitute notable drawbacks. In the process of esterase-active bacteria staining with carboxyfluorescein diacetate (CFDA), we have reported glutaraldehyde (GTA) affected the discriminative recognition of bacteria due to prevention of fluorescence leakage from the cell. In this study, CFDA was applied to four pure bacterial strains (two Gram-negative strains and two Gram-positive strains) during the exponential growth phase and to activated sludge as an indicator of microbial viability. GTA concentration was also optimized and the effect of GTA addition was compared to the conventional method using ethylenediamine tetraacetic acid (EDTA) and the control without pretreatment. At higher concentrations of GTA, microbial viability decreased because of GTA toxicity. In the case of all conditions where CFDA staining was carried out in the assay of microbial viability, the highest viability was achieved by using of 1g/L GTA.
Keywords: Carboxyfluorescein diacetate (CFDA); Cell viability; Glutaraldehyde; Activated sludge
Maximization of metabolite in fed-batch cultures by Hwa Sung Shin; Henry C. Lim (pp. 62-74).
Fed-batch fermentation for maximization of metabolite production at a final time is normally a singular control problem. The singular optimal feed rate strategy depends on relative position of peaks in the specific rates of cell growth μ, substrate consumption σ and product formation π. Regions in which singular feed rates exist are identified and variation of substrate concentration in the singular region is elucidated. Sufficient conditions for the existence of a singular arc are developed, which can be incorporated into an efficient and stable computational scheme to obtain the optimal feed rate profiles.
Keywords: Fed-batch culture; Control; Optimization; Modeling; Singular arc; Sufficient conditions
Immobilized algal cells used for hydrogen production by John J. Hahn; Maria L. Ghirardi; William A. Jacoby (pp. 75-79).
This paper explores the use of the photosynthetic green alga Chlamydomonas reinhardtii bound to solid support particles to produce hydrogen in a two-step cycle. Bound cells are more easily cycled between growth mode and hydrogen production mode. The data indicate that the presence of silica particles does not inhibit the growth of the algae in the sulfur rich growth media. Filtration experiments reveal that the algae effectively bind to the silica particles, as high removal efficiencies are observed. The silica particles appear to approach saturation algae at a mass-loading ratio of about 0.035. In hydrogen production mode, the bound algae perform about as well as free-floating algae in terms of cumulative hydrogen production. A full-factorial experiment is described in which algae concentration was deemed to have a significant effect on cumulative hydrogen production.
Keywords: Immobilized cells; Bioreactors; Filtration; Kinetic parameters
A simple and accurate method for simulation of hollow fiber biocatalyst membrane reactors by Elio E. Gonzo; Juan C. Gottifredi (pp. 80-85).
A recently developed technique to estimate effectiveness factor in catalytic pellets [J.C. Gottifredi, E.E. Gonzo, On the effectiveness factor calculation for a reaction-diffusion process in an immobilized biocatalyst pellet, Biochem. Eng. J. 24 (2005) 235–242] is used to greatly simplify the simulation of membrane biocatalyst reactors. The whole problem is reduced to well-known plug flow packed bed reactor after an appropriate definition of an effectiveness factor ( η) that takes into account chemical consumption in the catalytic region and mass transfer resistances of the reactive component. A standard R–K routine can then be applied since, at each mesh point, η is calculated through a non-linear algebraic equation.Results produced with this procedure compare fairly well with previous findings. Moreover some experimental results of kinetics studies related with enzyme immobilization are used to simulate membrane hollow fiber reactors and conversion, concentrations and η profiles along reactor axial position.The procedure can be applied to any biocatalytic system provided a single chemical reaction takes place although the kinetic expression can be arbitrary.
Keywords: Hollow fiber reactor; Effectiveness factor; Mass transport resistances; Immobilized enzyme; Reactor simulation
Multi-rate model predictive control of a chemical reactor based on three neural models by D.W. Yu; D.L. Yu (pp. 86-97).
This paper describes a multi-rate model predictive control for a chemical reactor rig. Three multi-input single-output neural network models are developed with different sampling times; each for one reactor output. A multi-rate control strategy is proposed based on the multi-rate models, which enables reduced dimension optimisations to be used in majority of searching for optimal controls. In addition, some practical control techniques are also applied. Effectiveness of the proposed method is evaluated by both simulations and on-line control. A comparison with three decentralised PID controllers is presented.
Keywords: Multi-rate control; Non-linear model predictive control; Adaptive neural networks; Chemical reactors; On-line implementation
Modeling of membrane-aerated biofilm: Effects of C/N ratio, biofilm thickness and surface loading of oxygen on feasibility of simultaneous nitrification and denitrification by Shinya Matsumoto; Akihiko Terada; Satoshi Tsuneda (pp. 98-107).
A multipopulation model of a membrane-aerated biofilm (MAB) considering heterotrophic bacteria (HB), ammonia-oxidizing bacteria (AOB), and nitrite-oxidizing bacteria (NOB) was constructed with the simulation software AQUASIM 2.1 to corroborate the process concept of the membrane-aerated biofilm reactor (MABR) and to reveal an operational range for high chemical oxygen demand (COD) and nitrogen removal efficiencies. The modeling results confirm that simultaneous nitrification and denitrification (SND) is feasible in the MAB but not in a top-down aerated biofilm (conventional biofilm) due to the absence of oxygen for AOB and NOB. The model precisely predicts the COD, NH4+-N, and T-N removal efficiencies and determines operating parameters like COD/nitrogen (C/N) ratio, biofilm thickness and surface loading of oxygen, which significantly affect SND efficiency. High nitrogen removal efficiency (more than 70%) is attained at ranges of C/N ratio from 3.0 to 5.25 and of biofilm thickness from 600 to 1200μm. In addition, it was clearly demonstrated that nitrogen removal not via nitrate but via nitrite could be achieved by controlling the relative surface loadings of oxygen and ammonia, supporting the feasibility of short-cut SND with MABs.
Keywords: AQUASIM; Biofilm modeling; Membrane-aerated biofilm (MAB); Simultaneous nitrification and denitrification (SND)
Direct purification and immobilization of recombinant hyaluronan lyase from unclarified feedstock using immobilized metal affinity magnetite for oligo-hyaluronan preparation by Pei-Fen Yang; Cheng-Kang Lee (pp. 108-115).
Submicron-size magnetite with metal chelating capability was prepared to directly and specifically recover recombinant hyaluronan (HA) lyase from unclarified E. coli cells lysate. The unclarified contaminants did not have significant effect on reducing the yield and purity of the recovered 6xHis tagged HA lyase. The recombinant HA lyase recovered on this immobilized metal affinity magnetite (IMAM) (12.0mg/g magnetite) was used as an immobilized enzyme to digest high molecular weight HA for the preparation of oligo-HA. Once immobilized, HA lyase activity decreased significantly to about 10% of its free activity. After an abrupt activity decrease in the first two batch reaction, 40% of the initial activity of IMAM immobilized HA lyase was maintained at the following three repeated batch reaction. The average size of the oligo-HA prepared was estimated to be about 1660Da by using the unsaturated oligo-HA concentration measured at OD232. However, the average molar mass of oligo-HA determined by MALDI-TOF-MS was around 1400.
Keywords: Magnetite; Metal chelator; Hyaluronan lyase; Immobilization; Hyaluronic acid; Oligosaccharides