Characterization ofStreptomyces sp. Strain DRS-1 and its ampicillin transformation product

Incubation of ampicillin with whole cells ofStreptomyces sp. DRS-1 resulted in accumulation of four compounds different from ampicillin. One of them was isolated, purified and partially characterized. On the basis of spectroscopic characteristics,R _F value and antibacterial activity the compound was identified as cephalexin. It could also be obtained from ampicillin by using crude protein extract of the strain.     

Palatinose production by free and Ca-alginate gel immobilized cells of Erwinia sp.

Palatinose is a non-cariogenic disaccharide obtained from the enzymatic conversion of sucrose, used in food industries as a sugar substitute. Free and Ca-alginate immobilized cells of Erwinia sp. D12 were used to produce palatinose from sucrose. Palatinose production was studied in a repeated-batch process using different immobilized biocatalysts: whole cells, disrupted cells and glucosyltransferase. Successive batches were treated with the immobilized biocatalyst, but a decrease in palatinose production was observed. A continuous process using a packed-bed reactor was investigated, and found to produce 55–66% of palatinose during 17 days using immobilized cells treated with glutaraldehyde and a substrate flow speed of 0.56 ml min⁻¹. However, immobilized cells in a packed-bed reactor failed to maintain the palatinose production for a prolonged period. The free cells showed a high conversion rate using batch fermentation, obtaining a palatinose yield of 77%. The cells remained viable for 16 cycles with high palatinose yields (65–77%). Free Erwinia sp. D12 cells supported high production levels in repeated-batch operations, and the results showed the potential for repeated reuse.     

Expandase-like activity mediated cell-free conversion of ampicillin to cephalexin by Streptomyces sp. DRS I

Cell-free extracts of Streptomyces sp. DRS I converted ampicillin to cephalexin, presumably due to the activity of the enzyme, expandase. The extract was fractionated and characterized by colorimetric and chromatographic measurements coupled with disc-agar diffusion bioassay against an ampicillin-resistant, cephalexin-sensitive E. coli strain. Though expandase could not be identified, the presence of a hitherto unreported expandase in Streptomyces sp. DRS I is suggested.     

Degradation of 2-methylnaphthalene by free and immobilized cells of Pseudomonas sp. strain NGK1

A Pseudomonas sp. strain NGK1 (NCIM 5120) capable of utilizing 2-methylnaphthalene (2-MN) was immobilized in various matrices namely, polyurethane foam (PUF), alginate, agar and polyvinyl alcohol (PVA) (1.5 × 10¹² c.f.u. g^–1 beads). The degradation rates of 25 and 50 mM 2-MN by freely suspended cells (2 × 10¹¹ c.f.u. ml^–1) and immobilized cells in batches, semi-continuous with shaken culture and continuous degradation in a packed-bed reactor were compared. The PUF-immobilized cells achieved higher degradation of 25 and 50 mM of 2-MN than freely suspended cells and the cells immobilized in alginate, agar or PVA. The PVA- and PUF-immobilized cells could be reused for more than 30 and 20 cycles respectively, without losing any degradation capacity. The effect of dilution rates on the rate of degradation of 25 and 50 mM 2-MN with freely suspended and immobilized cells were compared in the continuous system. Increase in dilution rate increased the degradation rate only up to 1 h^–1 in free cells with 25 mM 2-MN and no significant increase was observed with 50 mM 2-MN. With immobilized cells, the degradation rate increased with increase in dilution rate up to 1.5 h^–1 for 25 mM and 1 h^–1 for 50 mM 2-MN. These results revealed that the immobilized cell systems are more efficient than freely suspended cells for biodegradation of 2-MN.     

Steroid transformation using magnetically immobilized Mycobacterium sp.

Mycobacterium sp. (NRRL-B 3683) has been immobilized by adhesion of magnetic materials of submicron size to the bacterial surface. Preparations based on laboratory-prepared magnetic oxide that had been derivatized with hydrophobic octyltrichlorosilane showed the best properties. The magnetically immobilized bacteria were used for side-chain degradation of cholesterol into androsta-1,4-diene-3,17-dione. The magnetic bacteria behaved as free cells in the transformation media and no mass transfer limitations were observed. The magnetic bacteria could be used repeatedly without any cell loss, the cells being retrieved at the end of each transformation cycle by a magnet.     

Uranium accumulation by immobilized cells of aCitrobacter sp.

Uranium was removed from challenge flows presented to immobilized cells of aCitrobacter sp. In excess of 90% of the presented metal was recovered, giving high yields of accumulated metal which could be subsequently released from the immobilized cellsin situ.     

Strontium accumulation by immobilized cells of aCitrobacter sp.

Summary Immobilized cells of aCitrobacter sp. accumulated strontium at alkaline pH. Under optimum conditions in excess of 90% of the metal was removed from challenge flows.     

Microbial transformation of validamycin A to valienamine by immobilized cells

Immobilized Pseudomonas sp. HZ519 cells have been used for transformation of validamycin A to valienamine and the degradation pathway of validamycin A by Pseudomonas sp. HZ519 has also been studied. Substrate inhibition in immobilized cell system was avoided. An average of 8.6 g L^?1 valienamine concentration was obtained when concentration of validamycin A was increased up to 120 g L^?1. Through a treatment of the immobilized cells with 0.3 mol L^?1 substrate, the activity of the immobilized cells was increased distinctly. Compared with free cells, the productivity of valienamine by CA-immobilized cells was improved about three times. The reusability of the immobilized cells was evaluated with repeated–batch degradation experiments. The Tiele modulus was obtained from the experimental effectiveness factor. The result showed that the degradation process in the immobilized system was governed by intraparticle diffusion and chemical reaction.     

Microbial transformation of validamycin A to valienamine by immobilized cells

Immobilized Pseudomonas sp. HZ519 cells have been used for transformation of validamycin A to valienamine and the degradation pathway of validamycin A by Pseudomonas sp. HZ519 has also been studied. Substrate inhibition in immobilized cell system was avoided. An average of 8.6 g L^-1 valienamine concentration was obtained when concentration of validamycin A was increased up to 120 g L^-1. Through a treatment of the immobilized cells with 0.3 mol L^-1 substrate, the activity of the immobilized cells was increased distinctly. Compared with free cells, the productivity of valienamine by CA-immobilized cells was improved about three times. The reusability of the immobilized cells was evaluated with repeated-batch degradation experiments. The Tiele modulus was obtained from the experimental effectiveness factor. The result showed that the degradation process in the immobilized system was governed by intraparticle diffusion and chemical reaction.     

In vitro transformation of mouse testis cells by oncogene transfection

Germ cell tumors (GCTs) are unique in that they exhibit diverse biological characteristics and pathological features. Although several in vivo GCT models are available, studies on GCTs are hampered because in vivo development of GCTs is time consuming and prevents a detailed molecular analysis of the transformation process. Here we developed a novel strategy to transform mouse testis cells in vitro. Lentivirus-mediated transfection of dominant negative Trp53, Myc, and activated Hras1 into a CD9-expressing testis cells caused tumorigenic conversion in vitro. Although these cells resembled embryonic stem (ES) cells, they were aneuploid and lacked Nanog expression, which is involved in the maintenance of the undifferentiated state in ES cells. Euploid ES-like cells were produced by transfecting the Yamanaka factors (Pou5f1, Myc, Klf4, and Sox2) into the same cell population. Although these cells expressed Nanog, they were distinct from ES cells in that they expressed CD44, a cancer stem cell antigen. Both treatments induced similar changes in the DNA methylation patterns in differentially methylated regions of imprinted genes. Moreover, despite the differences in their phenotype and karyotype, both cell types similarly produced mixed GCTs on transplantation, which were composed of teratomas, seminomas, and embryonal carcinomas. Thus, in vitro testis cell transformation facilitates an analysis of the GCT formation process, and our results also suggest the close similarity between GCT formation and reprogramming.     

Bench scale production of butyramide using free and immobilized cells of Bacillus sp. APB-6

Bioprocess and Biosystems Engineering - Butyramide is a commodity chemical having wide range of applications from material science to biological sciences including synthesis of therapeutic drugs,...     

Trimethyl lead degradation by free and immobilized cells of an Arthrobacter sp. and by the wood decay fungus Phaeolus schweinitzii

Summary The continuing production of leaded petrol generates liquid wastes containing recalcitrant trialkyl lead, for which no suitable chemical treatment has been formulated. This investigation explores the feasibility of using microorganisms to catalyse the rate-limiting step of trimethyl lead degradation to dialkyl lead; this disproportionates chemically to give, ultimately, Pb²⁺ which is treatable by classical methods. An Arthrobacter sp. and a wood decay macrofungus, Phaeolus schweinitzii provide novel evidence for metabolic trimethyl lead (Me₃Pb⁺) degradation. The retention of this activity in immobilized cell column reactors challenged with Me₃Pb⁺-supplemented flows suggests that a future biotreatment process may be possible. Offprint requests to: M. E. Macaskie     

Heavy metal accumulation by immobilized cells of a Citrobacter sp.

Summary Immobilized cells of a strain of a Citrobacter sp. were effective in the removal of cadmium, lead and copper from single and mixed metal flows, and from synthetic effluents. About 80% of the presented metal was removed, and this was increased to nearly 100% by the incorporation of additional immobilized cell column units.     

Biosorption of Malathion by immobilized cells of Bacillus sp. S14

Abstract

Biosorption is potentially an attractive technology for the treatment of wastewater by removing pesticide molecules from dilute solutions. This study investigated the feasibility of an isolated Bacillus sp. S₁₄ immobilized in calcium alginate that was used as a biosorbent for Malathion removal from aqueous solutions in batch mode. The highest value of Malathion uptake by isolated Bacillus sp. S14 (1.33g L^?1, dry basis) immobilized in 3% calcium alginate was 64.4% at 25°C and pH7.0 when the initial Malathion concentration was 50 mg L^?1. Equilibrium was attained at 8h. The sorption data conformed well to the Fruendlich isotherm model.