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Biochemical Engineering Journal (v.27, #1)
A novel bioflocculant produced by Enterobacter aerogenes and its use in defecating the trona suspension by Wen-Yu Lu; Tong Zhang; Dong-Yan Zhang; Cai-Hong Li; Jian-Ping Wen; Lian-Xiang Du (pp. 1-7).
In this paper, a bioflocculant-producing bacterium, named W-23, was isolated from soil and identified as Enterobacter aerogenes. The bioflocculant (named WF-1) produced by W-23 was an acidic polysaccharide composed mainly of uronic acid (13.2%), pyruvic acid (7.4%) and acetic acid (1.6%). The three components sugars of WF-1 were glucose, fructose and manose, and the molar ratio was 10.3:5.4:1 for glucose:fructose:manose. The influence of factors like temperature, bioflocculant dosage and concentration of positive ions on the flocculation were studied. The optimal conditions were as follows: temperature 45°C, WF-1 90mg/L and Zn2+ 0.03mol/L. As a result, the sedimentation rate was 2.96×10−4m/s, and the OD of supernatant reached 0.05. The efficiency of the bioflocculant was better than that of conventional chemically synthesized flocculants, such as anionic polyacrylamide or non-ionic polyacrylamide.
Keywords: Bioflocculant; Trona; Defecation; Enterobacter aerogenes
Insect cells–Baculovirus system: Factors affecting growth and low MOI infection by You H. Zhang; Giora Enden; José C. Merchuk (pp. 8-16).
The use of low multiplicity of infection (MOI) for the production of baculovirus in insect cell sytems is an attractive alternative for large-scale production processes. Such processes may be focused on the production of biological insecticides or on the expression of medically useful foreign genes. In the present study, the effect of MOI, cell inoculum age and inoculation procedure (carry-over of spent medium from the pre-culture) was studied. While some influences of inoculum age and medium were found, the overhelming effect is related to MOI. The data obtained describe the dynamics of the changes of non-occluded virus (NOV) in time, giving a useful insight into the mechanism of the cell–virus system.
Keywords: Insect cell culture; Baculovirus; Infection dynamics
Extraction of volatile fatty acids (VFAs) from water hyacinth using inexpensive contraptions, and the use of the VFAs as feed supplement in conventional biogas digesters with concomitant final disposal of water hyacinth as vermicompost by P. Sankar Ganesh; E.V. Ramasamy; S. Gajalakshmi; S.A. Abbasi (pp. 17-23).
A procedure has been developed for extracting volatile fatty acids (VFAs) from water hyacinth (WH) using simple and inexpensive equipment of the type commonly available in the rural households of the third world countries. The VFAs thus extracted were used as feed supplement in cow dung-fed floating-dome biogas digesters. As tens of thousands of such digesters are in operation across the third world, the aim of these studies has been to provide for such digesters feed derived from phytomass, especially for use whenever animal dung is in short supply or is unavailable. The VFA extraction was based on aerobic/facultative degradation of water hyacinth and significant quantities were extracted from each WH charge daily for upto 6 days. When cow-dung slurry was fortified with the VFAs and fed to a conventional biogas digester, it yielded about 22% higher quantity of biogas per unit feed than was obtained from equivalent mass (dry weight basis) of the unfortified cow-dung slurry.The technique developed by us enables phytomass to be utilized as feed supplement in biogas digesters without causing the problems of solids accumulation, frothing and clogging known to be associated with phytomass feed. After VFAs have been extracted from it, the ‘spent’ water hyacinth was vermicomposted and used as soil conditioner-cum-fertilizer.
Keywords: Volatile fatty acids; Anaerobic fermentation; Two phase system; Water hyacinth; Biogas; Vermicomposting; Eudrilus eugeniae
Enhanced phosphorus biological removal from wastewater—effect of microorganism acclimatization with different ratios of short-chain fatty acids mixture by Yinguang Chen; Yan Liu; Qi Zhou; Guowei Gu (pp. 24-32).
Two activated sludge was acclimatized respectively with a lower and a higher ratio of propionic/acetic acid wastewater (i.e. biomass A and biomass P), and the effect of biomass acclimatization on enhanced phosphorus biological removal from acetic acid enriched wastewater was investigated. Due to biomass P having a higher biomass polyphosphate content, less glycogen degradation, and probably greater phosphorus accumulating organisms (PAO) fraction, it exhibited a greater phosphorus release (1.18mmol versus 0.94mmol) and PHB accumulation (2.66mmol-C versus 2.54mmol-C) than biomass A per gram mixed liquor volatile suspended solids (MLVSS) in anaerobic phase. During the aerobic stage, it took up much higher phosphorus (1.54mmol/g-MLVSS versus 1.17mmol/g-MLVSS) but degraded slightly less PHA (3.67mmol-C/g-MLVSS against 3.73mmol-C/g-MLVSS) than biomass A. Further studies revealed that since biomass P consumed less energy for the aerobic glycogen synthesis and cell growth, its lower PHA degradation did not result in a lower phosphorus uptake. Thus, the biomass acclimatized with a higher propionic/acetic acid wastewater displayed a much greater PHA utilization efficiency for phosphorus uptake (0.42mol-phosphorus/mol-C-PHA versus 0.31mol-phosphorus/mol-C-PHA) and a much higher phosphorus removal efficiency than with a lower one (95.76% against 65.75%).
Keywords: Phosphorus biological removal; Wastewater; Acetic acid; Propionic acid; AcclimatizationAbbreviations; AB; Active biomass; ATP; Adenosine triphosphate; DO; Dissolved oxygen; EBPR; Enhanced biological phosphorus removal; GAO; Glycogen accumulating organisms; Gly; Glycogen; MCRT; Mean cell residence time; MLSS; Mixed liquor suspended solids; MLVSS; Mixed liquor volatile suspended solids; NADH; 2; Reduced nicotinamide adenine dinucleotide; PAO; Phosphorus accumulating organisms; PHA; Polyhydroxyalkanoates; PHB; Poly-3-hydroxybutyrate; PHV; Poly-3-hydroxyvalerate; Poly-P; Polyphosphate; SBR; Sequence batch reactor; SCFA; Short-chain fatty acids; SOP; Soluble ortho-phosphate; TCA; Tricarboxylic acid; TP; Total phosphate
High-speed chromatographic purification of plasmid DNA with a customized biporous hydrophobic adsorbent by Yuan Li; Xiao-Yan Dong; Yan Sun (pp. 33-39).
Interest in producing large quantities of plasmid DNA has recently increased as a result of the rapid evolution of gene therapy and DNA vaccines. Hydrophobic chromatography is a popular technique in the downstream processing of plasmid DNA. However, the low capacity and the high mass transfer resistance of most commercially available packings for bio-macromolecules limit their application in a large-scale process. In this work, a hydrophobic absorbent with wide pores was synthesized by the solid porogenic method. Analyses by scanning electron microscopy and mercury intrusion porosimetry revealed that the matrix contained two families of pores, i.e., micropores smaller than 100nm and superpores of 500–7300nm. The superpores provided not only convective flow channels for the mobile phase, but also a large surface for biomolecules binding. So the chromatographic process can be operated at high flow rate with high column efficiency and low backpressure as identified on a 2-mL column (5mm i.d., 2cm length). With a loading up to 2.6mg of 5.4kb plasmid (pcDNA3) in 8mL feedstock and operated at a flow rate as high as 20cm/min, nearly 100% of plasmid was recovered with a purity of 100%. The results indicate that the hydrophobic medium is promising for high-speed purification of plasmid DNA.
Keywords: Plasmid DNA; Hydrophobic interaction chromatography; Biporous medium; Purification; High speed
The pilot study for oil refinery wastewater treatment using a gas–liquid–solid three-phase flow airlift loop bioreactor by Liu Xianling; Wen Jianping; Yuan Qing; Zhao Xueming (pp. 40-44).
Aerobic bio-treatment of the refinery wastewater was carried out in a 170m3 pilot-scale gas–liquid–solid three-phase flow airlift loop bioreactor (ALR) with a low ratio of height to diameter ( s), in which biological membrane replaced the activated sludge. The influences of pH value, air flow rate (AFR) and hydraulic residence time (HRT) on COD and ammonia nitrogen (NH4–N) reductions were investigated and discussed. The optimum operation condition was obtained as pH value 7.0–8.0, AFR 3.2m3 air (m3liquidh)−1 and HRT 6.5h. Under the optimum operation condition, the effluent COD and NH4–N were lower than 100 and 15mgL−1, respectively for more than 40 days, which have achieved the national primary discharge standard of PR China (GB 8978-1996). Furthermore, this pilot-scale airlift loop bioreactor generated only one-third of the sludge waste compared to the traditional activated sludge process.
Keywords: Gas–liquid–solid three-phase; Fluidized bed bioreactor; Pilot-scale; Low ratio of height to diameter; Wastewater treatment
Diffusion of substrate and oxygen in aerobic granule by Yong Li; Yu Liu (pp. 45-52).
In this study, one-dimensional models were developed to simultaneously describe diffusion of substrate and dissolved oxygen in aerobic granule under various conditions in sequencing batch reactor (SBR), meanwhile the models were further applied to predict changes of the bulk substrate concentration in the course of SBR operation. The proposed models were solved numerically by the Numerical Finite Difference Methods without making any additional assumptions. Results showed that diffusions of substrate and dissolved oxygen in aerobic granule would be a dynamic process, and they were closely interrelated. For aerobic granules with a size smaller than 0.4mm, no diffusion limitation of substrate and dissolved oxygen occurred. However, when aerobic granules grew to a size larger than 0.5mm, dissolved oxygen became a major limiting factor of metabolic activity of aerobic granule over substrate. These imply that the optimal size of aerobic granule would be less than 0.5mm in the sense of mass transfer. It was revealed that the substrate removal rate was inversely related to the size of aerobic granules, the substrate removal rate by aerobic granules with a size of 0.5mm was almost three times of that by aerobic granules with a size of 1mm.
Keywords: Diffusion; Dissolved oxygen; Modeling; Kinetic parameters; Substrate; Aerobic granule
A strategy of phosphorus feeding for repeated fed-batch fermentation of penicillin G by Xiao-Bing Li; Guang-Rong Zhao; Ying-Jin Yuan (pp. 53-58).
The critical “withdraw and fill� procedure is adopted for the efficient industrial fermentation of Penicillium chrysogenum to produce penicillin G. In order to maintain the elemental balance of the growing mycelia and to provide optimal conditions for penicillin G biosynthesis, a novel strategy of phosphorus feeding is reported. The required phosphorus to feed was calculated by the mass flow distribution and the phosphorus composition of the growing mycelia. The optimal amount of supplied phosphorus was experimentally determined for repeated fed-batch process. Initially, inorganic phosphorus source, such as KH2PO4, was effective. But, a combination of inorganic KH2PO4 with organic phosphorus, such as corn steep liquor, showed the best results. Feeding KH2PO4 together with corn steep liquor after the first withdrawal improved the penicillin titers by 16.1% on average. Our fermentation experiments and validation processes showed that feeding phosphorus was an efficient way to improve the production of penicillin G. This phosphorus feeding strategy might also be useful to improve the fermentation processes of other industrial biological products.
Keywords: Penicillin; Filamentous fungi; Fermentation; Fed-batch culture; Optimization; Phosphorus-feeding
Residence time distribution in microbial fuel cell and its influence on COD removal with electricity generation by Hyunsoo Moon; In Seop Chang; Jae Kyung Jang; Byung Hong Kim (pp. 59-65).
The liquid flow characteristics in a microbial fuel cell (MFC) were determined using a residence time distribution (RTD) test, and its effects on the performance of the MFC were investigated in terms of electricity generation and chemical oxygen demand (COD) removal. A membrane-less MFC was used with two different anode structures; normal graphite felt disk (“Normal� MFC) and perforated graphite felt disk (“Perforated� MFC). The RTD results showed that there exists nonideal flows such as channeling and tailing in the “Normal� MFC and the flow characteristics were much better in the “Perforated� MFC with the improved electricity generation. COD removal rate was similar between the MFCs. These results show that the flow characterization is an important area of study for the optimization of an MFC.
Keywords: Biodegradation; Bioprocess design; Mass transfer; Microbial fuel cell; Residence time distribution; Waste-water treatment
Novel enzymatic route for kinetic resolution of (±)1,4-benzodioxan-2-carboxylic acid by Sangita M. Kasture; Rita Varma; Uttam R. Kalkote; Sanjay Nene; Bhaskar D. Kulkarni (pp. 66-71).
Ethyl 1,4-benzodioxan-2-carboxylate is used as an intermediate compound for the production of drug doxazosin mesylate. The title compound was kinetically resolved to get S-enantiomer of ethyl 1,4-benzodioxan 2-carboxylate in a simple lipase catalyzed transesterification reaction. Ethyl acetate was used as reaction medium as well as acyl donor. The influence of the enzyme source and time of reaction on the enantio selectivity of product were studied. Lipase from Candida antartica-B (Novozyme A/S) catalyzed transesterification reaction with good enantio selectivity towards S-enantiomer. The high enantiomeric ratio, E=160, provided S-2 an acceptable chemical yield (50%) and enantiomeric excess (>95%).
Keywords: Lipases; Ethyl 1,4-benzodioxan-2-carboxylate; 1,4-Benzodioxan-2-carboxylic acid; Doxazosin; Transesterfication; Ethyl acetate; Enantio selectivity; Enantiomeric ratio
Manipulation of morphological transition in Saccharomyces cerevisiae mutant J19 by Jaruwan Maneesri; Masayuki Azuma; Koichi Igarashi; Akio Sugihara; Hiroshi Ooshima (pp. 72-76).
Saccharomyces cerevisiae has the potential for morphological differentiation. In order to positively utilize the morphological transition of S. cerevisiae for the separation of cells from culture broth, the cell settling of mutant J19 having pseudohyphal form was examined. Mutant cells settled faster in stationary test tubes than those of the parental strain having yeast-like form. Furthermore, in an attempt to establish a basis for manipulation of the morphological transition between the yeast-like and pseudohyphal forms, a plasmid harboring the SCL1 gene under the control of the GAL1 promoter was constructed. The SCL1 gene complements the morphological phenotype of mutant J19. The plasmid was transformed into mutant J19, and the morphological transition of the transformant by changes in carbon source was examined. It was found that partial manipulation of the morphological transition was possible.
Keywords: Yeast; Control; Separation; Microbial growth; Morphogenetic transition; Cell shape
Two-stage process design for the biodesulphurisation of a model diesel by a newly isolated Rhodococcus globerulus DAQ3 by Jianzhong Yang; Ian W. Marison (pp. 77-82).
New bacteria were enriched and isolated from oil-contaminated soils and desulphurisation activity was compared with reported bacterial strains. Of the six different bacterial strains, a newly isolated Rhodococcus globerulus DAQ3 showed the highest activity and stability for desulphurisation of dibenzothiophene (DBT) in a two-phase system. The overall average production rate of 2-hydroxybiphenyl was 18μmol/g DCW/h during 9h, which was over two-fold higher than the reference strain Rhodococcus erythropolis IGTS8. Based on the activity analysis, metabolite inhibition in the aqueous phase was proven, then a two-stage bioprocess was developed for the desulphurisation of a model diesel, and as a result, the new strain DAQ3 reduced the total sulphur in the model diesel by 33%, with DBT conversion of 65%, within 48h.
Keywords: Biodesulphurisation; Resting cell activity; Product inhibition; Process integration; Rhodococcus globerulus; Model diesel
Removal of methylene blue by mango seed kernel powder by K. Vasanth Kumar; A. Kumaran (pp. 83-93).
Batch experiments were carried out for the sorption of methylene blue onto mango seed kernel particles. The operating variables studied were initial solution pH, temperature, adsorbent mass, initial dye concentration and contact time. Equilibrium data were fitted to Freundlich and Langmuir isotherm equation and the equilibrium data were found to well represented by Langmuir isotherm equation. The monolayer sorption capacity of mango seed kernel for methylene blue sorption was found to be 142.857mg/g at 303K. The sorption kinetics was found to follow pseudo first order kinetic model. The methylene blue uptake process was found to be controlled by both surface and pore diffusion with surface diffusion at the earlier stages followed by pore diffusion at later stages. The average effective diffusion coefficient was calculated and found to be 5.66×10−4cm2/s. Analysis of sorption data using Boyd plot confirms that the external mass transfer as the rate limiting step in the sorption process. Various thermodynamic parameters such as enthalpy of sorption Δ H, free energy change Δ G and entropy Δ S were estimated. The positive value of Δ H and negative values of Δ G shows the sorption process is exothermic and spontaneous. The positive value of entropy Δ S shows the increased randomness at the solid–liquid interface during the sorption of dye ions onto mango seed kernel particles.
Keywords: Sorption; Mango seed kernel; Methylene blue; Kinetics; Equilibrium; Mechanism; Thermodynamic