Physiological aspects of immobilised Aspergillus niger cells producing polymethylgalacturonase

Monascus Yellow Pigment Production by Coupled Immobilized-Cell Fermentation and Extractive Fermentation in Nonionic Surfactant Micelle Aqueous Solution

Microbial fermentation with immobilized cells possesses many advantages. However, this fermentation mode is restricted to the production of extracellular products. Our previous study demonstrated that the extractive fermentation of Monascus spp. in nonionic surfactant micelle aqueous solution can export Monascus pigments that are supposed to be mainly intracellular products to extracellular culture broth and, in the meantime, extracellularly enhance the production of yellow pigments at a low pH condition; consequently, this makes the continuous production of yellow pigments with immobilized Monascus cells feasible. In this study, immobilized-cell fermentation and extractive fermentation in Triton X-100 micelle aqueous solution were successfully combined to continuously produce Monascus yellow pigments extracellularly. We examined the effects of cell immobilization and Triton X-100 on cell growth, pigment production, and pigment composition. In the repeated-batch extractive fermentation with immobilized cells, the biomass in Ca-alginate gel beads continued to grow and reached 21.2 g/L after seven batches, and dominant yellow pigments were produced extracellularly and stable for each batch. The mean productivity of the extracellular yellow pigments reached up to 22.31 AU410 nm/day within the first four batches (13 days) and 19.7 AU410 nm/day within the first seven batches (25 days). The results also provide a new strategy for producing such intracellular products continuously and extracellularly.

Effective bioconversion of sophoricoside to genistein from Fructus sophorae using immobilized Aspergillus niger and Yeast

In this study, sophoricoside from Fructus sophorae was highly bioconversed to genistein by co-immobilized Aspergillus niger and Yeast. Bioconversion conditions for genistein were optimized with single-factor experiments. The optimal conditions were as follows: microbial concentration 1.5 × 10(7) cells/mL, wet weight of microorganisms beads 10.0 g/g material, pH 5, ratio of liquid to solid 25:1 (mL/g), temperature 32 °C and time 24 h. Under these conditions, a 34.45-fold increase in production of genistein was observed with a bioreactor. Moreover, the antioxidant activities of the extracts from the fermented and untreated F. sophorae were 0.287 ± 0.11, 0.384 ± 0.08 mg/mL (IC50) and 1.84 ± 0.13, 1.28 ± 0.25 mmol Fe(II)/g, according to the DPPH test and FRAP assay, respectively. The results indicated that the method described in the current work were valuable procedure for the production of genistein, which is of most importance for industrial scale applications as well as food industry.

Production of glucose oxidase and catalase by Aspergillus niger free and immobilized in alginate-polyvinyl alcohol beads

The production of glucose oxidase (GOX) and catalase (CAT) by submerged fermentation of the free and immobilized xerophytic fungus Aspergillus niger under equal conditions was compared. To immobilize fungal spores, entrapment in PVA/alginate beads treated with NaNO3/CaCl2 was performed. The yield of immobilization in the beads with a diameter less than 1mm was equal to 100%. Fungus growth and substrate consumption were evaluated in both fermentation systems, demonstrating the lag-period presence in the case of the first cycle of immobilized fungus use. The enzyme production by immobilized fungus reuse was carried out. In these cases, greater enzymatic GOX activity was detected, while CAT activity decreased. SEM micrographs for the beads with immobilized fungus applied in the first and second fermentation cycles were obtained, presenting fungus spreading inside the sphere, spore presence and branching hyphae. Immobilization of A. niger on PVA/alginate beads is effective for GOX and CAT production at least on 2-3 repeated fermentative cycles. Thus, immobilization enables repeated use of microbial cells.

Preparation of Microbiological Agents for Organic Pollutants Removal in Wastewater

The authors have investigated the biochemical aspects of degradation processes of persistent organic compound benzothiazole by immobilized Rhodococcus rhodochrous cells, such as entrapped in Ca-alginate beads, or as being immobilized on some solid carries. The mineralization of toxicant was complete and biodestructive capacity of entrapped in alginate bacteria increased with each new experimental cycle.

Immobilized viable microbial cells: from the process to the proteome… or the cart before the horse

Biotechnological processes based on immobilized viable cells have developed rapidly over the last 30 years. For a long time, basic studies of the physiological behaviour of immobilized cells (IC) have remained in the shadow of the applications. Natural IC structures, i.e. biofilms, are being increasingly investigated at the cellular level owing to their definite importance for human health and in various areas of industrial and environmental relevance. This review illustrates this paradoxical development of research on ICs, starting from the initial rationale for IC emergence and main application fields of the technology--with particular emphasis on those that exploit the extraordinary resistance of ICs to antimicrobial compounds--to recent advances in the proteomic approach of IC physiology.

Comparison of antioxidant enzyme biosynthesis by free and immobilized Aspergillus niger cells*

Effect of immobilization on antioxidant enzyme synthesis by growing and non-growing cell culture of Aspergillus niger 26 was studied. Entrapped cells showed a greater than 1.5-fold increase in the superoxide dismutase (SOD) activity and a moderate elevation in catalase activity. The immobilization did not cause changes in the spectrum of SOD isoenzymes. The observed increase in SOD activity required de novo synthesis of this enzyme, because it was suppressed by inhibitors of the transcription and translation. The addition of various viscous substances (agar, Na-alginate and pectin) stimulated the SOD synthesis. Despite these results, it was found that the changes in SOD activity are induced in response to growth in the state of immobilization rather than to presence of alginate. Immobilized A. niger cells exhibited about a 4- to 5-fold higher level of cyanide-resistant respiration. This latter phenomenon might use as an indicator of intracellular oxy-intermediate generation in cell culture growing under stress conditions. The results are discussed relative to association between physiological stress caused by immobilization and oxidative stress.