Biological particles of given size, shape, and density for use in biological reactors

Scale-up of PUF-immobilized fungal chitosanase-lipase preparation production

Mucor circinelloides IBT-83 mycelium that exhibits both lipolytic (A_L) and chitosanolytic (A_CH) activities was immobilized into polyurethane foam in a 30 L laboratory fermenter. The process of immobilization was investigated in terms of the carrier porosity, its type, amount, and shape, location inside the fermenter, mixing, and aeration parameters during the culture, as well as downstream processing operations. The selected conditions allowed for immobilization of approximately 7 g of defatted and dried mycelium in 1 g of carrier, i.e., seven times more than achievable in 1 L shake-flasks. Enzymatic preparation obtained by this method exhibited both the chitosanolytic (A_CH 432.5 ± 6.8 unit/g) and lipolytic (A_L 150.0 ± 9.3 U/g) activities. The immobilized preparation was successfully used in chitosan hydrolysis to produce chitooligosaccharides and low molecular weight chitosan, as well as in waste fats degradation and in esters synthesis in nonaqueous media. It was found that the half-life of immobilized preparations stored at room temperature is on average of 200 days.

Application of biofilm bioreactors in white biotechnology

The production of valuable compounds in industrial biotechnology is commonly done by cultivation of suspended cells or use of (immobilized) enzymes rather than using microorganisms in an immobilized state. Within the field of wastewater as well as odor treatment the application of immobilized cells is a proven technique. The cells are entrapped in a matrix of extracellular polymeric compounds produced by themselves. The surface-associated agglomerate of encapsulated cells is termed biofilm. In comparison to common immobilization techniques, toxic effects of compounds used for cell entrapment may be neglected. Although the economic impact of biofilm processes used for the production of valuable compounds is negligible, many prospective approaches were examined in the laboratory and on a pilot scale. This review gives an overview of biofilm reactors applied to the production of valuable compounds. Moreover, the characteristics of the utilized materials are discussed with respect to support of surface-attached microbial growth.

Biocatalysis for biobased chemicals

The design and development of greener processes that are safe and friendly is an irreversible trend that is driven by sustainable and economic issues. The use of Biocatalysis as part of a manufacturing process fits well in this trend as enzymes are themselves biodegradable, require mild conditions to work and are highly specific and well suited to carry out complex reactions in a simple way. The growth of computational capabilities in the last decades has allowed Biocatalysis to develop sophisticated tools to understand better enzymatic phenomena and to have the power to control not only process conditions but also the enzyme's own nature. Nowadays, Biocatalysis is behind some important products in the pharmaceutical, cosmetic, food and bulk chemicals industry. In this review we want to present some of the most representative examples of industrial chemicals produced in vitro through enzymatic catalysis.

Current and future trends for biofilm reactors for fermentation processes

Biofilms in the environment can both cause detrimental and beneficial effects. However, their use in bioreactors provides many advantages including lesser tendencies to develop membrane fouling and lower required capital costs, their higher biomass density and operation stability, contribution to resistance of microorganisms, etc. Biofilm formation occurs naturally by the attachment of microbial cells to the support without use of any chemicals agent in biofilm reactors. Biofilm reactors have been studied and commercially used for waste water treatment and bench and pilot-scale production of value-added products in the past decades. It is important to understand the fundamentals of biofilm formation, physical and chemical properties of a biofilm matrix to run the biofilm reactor at optimum conditions. This review includes the principles of biofilm formation; properties of a biofilm matrix and their roles in the biofilm formation; factors that improve the biofilm formation, such as support materials; advantages and disadvantages of biofilm reactors; and industrial applications of biofilm reactors.

Recycle in fermentation processes

Until recently, the recycle of the solid (microbial), liquid, or gaseous phases in microbiological processes has only been practiced rarely, with the notable exception of activated sludge processes for wastewater treatment, where recycling of a large fraction of the microbial phase is essential for process stability and performance. During the last decade, the economic impact of a number of politically motivated changes with respect to energy and feedstock costs and availability, and legislation directed towards markedly higher levels of environmental protection have encouraged the evaluation and subsequent development of recycle technology in the fermentation industry. Many of the developments have occurred in isolation and some have failed to result in either an improvement in process economics or any reduction in the quantity of pollutants discharged. This article seeks to review the present diversity of approaches to recycle technology in fermentation processes in order to provide a sensible basis for future developments.

Ferrous iron oxidation by foam immobilized Acidithiobacillus ferrooxidans: Experiments and modeling

Ferrous iron bio-oxidation by Acidithiobacillus ferrooxidans immobilized on polyurethane foam was investigated. Cells were immobilized on foams by placing them in a growth environment and fully bacterially activated polyurethane foams (BAPUFs) were prepared by serial subculturing in batches with partially bacterially activated foam (pBAPUFs). The dependence of foam density on cell immobilization process, the effect of pH and BAPUF loading on ferrous oxidation were studied to choose operating parameters for continuous operations. With an objective to have high cell densities both in foam and the liquid phase, pretreated foams of density 50 kg/m(3) as cell support and ferrous oxidation at pH 1.5 to moderate the ferric precipitation were preferred. A novel basket-type bioreactor for continuous ferrous iron oxidation, which features a multiple effect of stirred tank in combination with recirculation, was designed and operated. The results were compared with that of a free cell and a sheet-type foam immobilized reactors. A fivefold increase in ferric iron productivity at 33.02 g/h/L of free volume in foam was achieved using basket-type bioreactor when compared to a free cell continuous system. A mathematical model for ferrous iron oxidation by Acidithiobacillus ferrooxidans cells immobilized on polyurethane foam was developed with cell growth in foam accounted by an effectiveness factor. The basic parameters of simulation were estimated using the experimental data on free cell growth as well as from cell attachment to foam under nongrowing conditions. The model predicted the phase of both oxidation of ferrous in shake flasks by pBAPUFs as well as by fully activated BAPUFs for different cell loadings in foam. Model for stirred tank basket bioreactor predicted within 5% both transient and steady state of the experiments closely for the simulated dilution rates. Bio-oxidation at high Fe(2+) concentrations were simulated with experiments when substrate and product inhibition coefficients were factored into cell growth kinetics.

Optimization of biodiesel production catalyzed by fungus cells immobilized in fibrous supports

A circulating packed-bed bioreactor system using fibrous nonwoven fabric as the immobilization matrix was suitable for simultaneous cell growth and immobilization of Rhizopus oryzae fungus cells, which could be used for lipase-mediated production of biodiesel by methanolysis of soybean oil. Response surface methodology and 5-level-5-factor central composite rotatable design was proved to be a powerful tool for the optimization of methanolysis conditions catalyzed by immobilized R. oryzae whole cell biocatalyst. A quadratic polynomial regression model was used to analyze the relationship between the yield and the significant reaction parameters. The analysis confirmed that water content, molar ratio of methanol to oil, cell weight, and reaction time were the significant factors affecting the yield at a 95% confidence level (p < 0.05). Under the optimum condition at 10.97% (w/w) water content, 0.64 molar ratio of methanol to oil, 2.25% (w/w) cell weight, and 23.3 h reaction time, the predicted value of yield was 72.6%. Validation experiments with yields of 70.77 +/- 2.46% verified the availability and the accuracy of the model.

Use of a whole-cell biocatalyst to produce biodiesel in a water-containing system

This study examined the use of a whole-cell biocatalyst to transesterify triglycerides, including high-Free Fatty Acid (FFA) waste greases, in a water-containing system. The whole-cell biocatalyst derived from Rhizopus oryzae (ATCC10260) was grown and reacted at room temperature without immobilization. The effectiveness of improving biodiesel yield through alteration of reaction temperature, additional alcohol, and additional transesterification reaction was also examined. Results showed that whole-cell biocatalyst was able to produce biodiesel with a yield of about 75% for virgin canola oil, 80% for waste vegetable oil and 55% for brown grease with a 72-hr transesterification reaction using no excess methanol. Elevating the reaction temperature to 35 degrees C significantly diminished the yield. An additional dose of methanol with another 24 hours of reaction time or a second 72-hr reaction resulted in biodiesel yield approaching 90% and only 3% residual glycerides (mono-, di- and tri-glycerides). These results suggest that whole-cell biocatalysts are able to transesterify waste oils or greases that are high in FFA and contain water. Brown (trap) grease and similar degraded or complex greases may be good candidates for further whole-cell biocatalyst research.

Whole-cell biocatalysts for biodiesel fuel production

Biodiesel fuel (BDF), which refers to fatty acid alkyl esters, has attracted considerable attention as an environmentally friendly alternative fuel for diesel engines. Alkali catalysis is widely applied for the commercial production of BDF. However, enzymatic transesterification offers considerable advantages, including reducing process operations in biodiesel fuel production and an easy separation of the glycerol byproduct. The high cost of the lipase enzyme is the main obstacle for a commercially feasible enzymatic production of biodiesel fuels. To reduce enzyme associated process costs, the immobilization of fungal mycelium within biomass support particles (BSPs) as well as expression of the lipase enzyme on the surface of yeast cells has been developed to generate whole-cell biocatalysts for industrial applications.

Immobilization of Escherichia coli cells using porous support particles coated with cationic polymers

The technique of cell immobilization using porous biomass support particles (BSPs), which is attractive from the point of view of simplicity and convenience, relies on the inherent ability of adhesive cells, as a consequence of their growth, to form films around the support material or the ability of flocculent cells to create flocs within the porous structure. In the present study, the immobilization of Escherichia coli cells using BSPs was investigated in shake-flask culture. The density of the cells immobilized within the BSPs was evaluated by measuring their intracellular lactate dehydrogenase (LDH) activity. Since E. coli K12 cells were not successfully retained within reticulated polyvinyl formal (PVF) resin BSPs with matrices of relatively small pores (pore diameter 60 microm), coating the surface of the BSPs with various polymers was examined as a way of promoting cell attachment. When positively charged polyamino acids such as poly-L-lysine, poly-L-arginine, poly-L-histidine, and poly-L-ornithine were adsorbed onto the particle surface, they were found to increase the immobilized cell density, while neutral and negatively charged polyamino acids including poly-L-asparagine and poly-L-glutamic acid were not effective. These results indicate that E. coli cells can be efficiently immobilized in PVF resin BSPs by electrostatic interaction between the negatively charged ions of the cell surface and the positively charged polymers adsorbed onto the BSP surface. A significantly high immobilized cell density was also achieved by coating the surface of the BSPs with the synthetic polymeric amine polyethyleneimine.

Lipase localization in Rhizopus oryzae cells immobilized within biomass support particles for use as whole-cell biocatalysts in biodiesel-fuel production

To identify the lipase responsible for the methanolysis activity of fungus whole-cell biocatalysts, the lipase localization of Rhizopus oryzae cells was determined. Western blot analysis showed that R. oryzae cells produce two types of lipase with different molecular masses of 34 and 31 kDa; the former (ROL34) was bound to the cell wall, whereas the latter (ROL31) was mainly bound to the cell membrane. It was found that cell immobilization within reticulated polyurethane foam biomass support particles strongly inhibits the secretion of membrane-bound lipase into the culture medium. An investigation of the relationship between ROL34 and ROL31 suggested that ROL31 originates from the cleavage of a 28-amino-acid residue at the N-terminus of ROL34. The addition of olive oil to the culture medium led to the retention of increased amounts of lipase within the cell. This phenomenon was further confirmed by an immunofluorescence labeling of hyphal cells. When cells were cultivated with various substrate-related compounds, such as olive oil and oleic acid, the intracellular methanolysis activity strongly correlated with the relative amounts of the membrane-bound lipase, which suggests that ROL31 localized in the membrane plays a crucial role in the methanolysis activity of R. oryzae cells.

Production of recombinant protein by baculovirus-infected insect cells in immobilized culture using porous biomass support particles

Immobilization of insect cells using porous biomass support particles (BSPs) and production of a recombinant protein by the immobilized cells after infection with a baculovirus were investigated in a shake-flask culture. Sf9 cells were passively immobilized in reticulated polyvinyl formal (PVF) resin BSPs (2 x 2 x 2 mm cubes) with matrices of 60 mum mean pore diameter in situ in shake-flasks. The cell density in the BSPs was over 5 x 10(7) cells/cm3-BSP in cultures with regular replacement of the culture medium, as estimated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. After infection with a recombinant baculovirus carrying the beta-galactosidase gene, immobilized cells within the BSPs showed a high specific productivity, comparable to the maximum productivity in shake-flask cultures of non-immobilized cells, as long as nutrients in the medium were not depleted. Even when immobilized cells at a high density of 5 x 10(7) cells/cm3-BSP were infected with the baculovirus, efficient beta-galactosidase production with a high specific productivity was possible by replacing the medium at appropriate intervals to avoid nutrient depletion.

Effect of support materials on antibiotic MSW2000 production by immobilized Streptomyces violatus

The production of an antibiotic by free and immobilized cells of Streptomyces violatus through entrapment or adsorption on different materials was investigated. S. violatus entrapped in Ca-alginate beads gave low antibiotic activity compared to the free cell or adsorbed cell, while the adsorption of S. violatus on sponge cubes yielded the highest antibiotic concentration after 4 days of incubation in static cultures. A starch concentration of 10 g/L was optimum for the production of the antibiotic by adsorbed cells. The weight and size of the sponge cubes used for immobilization influenced production of the antibiotic and the optimum weight and size of the sponge were 0.8 g and 1.0 cm(3), respectively, yielding a maximum antibiotic production of 280 mg/ml. Maximum antibiotic production was obtained at an initial pH value of 7.5 and in an inoculum size of 3 ml (spore suspension) per 50 ml. The production of the antibiotic in a fixed-bed bioreactor reached a maximum value after 2 days of incubation at a circulation rate of 30 ml/h. The immobilized cells in the bioreactor were reused seven successive times over a period of 14 days.

Manipulating secondary metabolism in cultured plant cells

This review attempts to present an overall strategy for the production of useful secondary metabolites by cultured plant cells. After consideration of the nature and utility of secondary metabolites and the possible role of these substances to the plant, the review focuses attention on the properties of the plant cells in culture and how the cell populations and their physical and chemical environment can be manipulated to encourage the synthesis and accumulation of secondary products. Finally, consideration is given to the involvement of genetic engineering in the production of cells to perform particular metabolic tasks and how these techniques might contribute to the development of a new strategy to enable the production of useful secondary metabolites on a commercial scale. CONTENTS Summary 553 I. Introduction 553 II. Development of a strategy 555 III. Concluding remarks 565 Acknowledgements 565 References 565.