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1	Cellular differentiation and antibiotic production by Streptomyces nodosus immobilised in alginate capsules Pereira, Tanya, University of Western Sydney, College of Health and Science, School of Natural Sciences January 2007 (has links) Encapsulation is a novel technique that involves the entrapment of materials such as cells, enzymes or chemicals within a semi-permeable matrix and is being explored as a drug delivery system. This project investigated the encapsulation of Streptomyces nodosus in alginate to assess whether this organism can produce the antifungal drug amphotericin B from within the matrix. New methods were developed to immobilise S. nodosus mycelia and spores in alginate capsules, assess bacterial viability and detect ng mL–1 quantities of amphotericin B in culture fluids. When capsules were cultured and cell proliferation was encouraged, organisms formed protrusions on the surface of the capsules. Differentiated branched hyphae that never progressed to sporogenic hyphae were observed on the surface of these structures. Viability was maintained for up to 30 days and low levels of amphotericin B were produced. The emergence of a co-existing free-dwelling population was also observed. Culturing immobilised organisms using conditioned media from an amphotericin deficient S. nodosus strain, augmented the development of the free-dwelling population resulting in the detection of amphotericin B in the culture fluid and full differentiation to sporogenic hyphae. This is the first report of sporulation of S. nodosus in liquid environments and demonstrates that immobilised S. nodosus can produce antibiotics. The sporulation of free-dwelling organisms was also induced using conditioned media and manipulation of quorum size, indicating a solid surface is not required for sporulation. Conditioned media from other Streptomyces spp. induced variable responses including sporulation, pigment formation and antibiotic production, possibly demonstrating communication between species and/or alteration in nutritional status. This new model for the life cycle of S. nodosus will permit the study of developmental pathways, antibiotic production, microbial community structure and inter-species and intra-species signalling. / Doctor of Philosophy (PhD) streptomyces nodosus streptomyces genetics antibiotics biotechnology Amphotericin B antifungal agents microencapsulation
2	In vitro polyketide biocatalysis : triketide building-blocks and enzymology Harper, Andrew David 08 October 2013 (has links) Polyketide products are useful compounds to research and industry but can be difficult to access due to their richness in stereogenic centers. Type I polyketide synthases offer unique engineering opportunities to access natural stereocontrol and resultant complex compounds. The development of a controlled in vitro platform based around type I polyketide synthases is described. It has been used to produce a small library of polyketide fragments on an unprecedented and synthetically-relevant scale and explore polyketide synthase enzymology. / text In vitro Cell-free Preparative Polyketide Polyketide synthase Ketoreductase Malonyl-CoA ligase MatB Enzymology Chiral building blocks Chiral synthons Diketide Triketide Lactone Ketolactone Natural products Secondary metabolism Secondary metabolite Modular Type I polyketide synthase Biosynthesis Streptomyces coelicolor Saccharopolyspora erythraea Bacillus subtilis Streptomyces nodosus Saccharomyces cerevisiae Streptomyces antibioticus Streptomyces venezuelae Saccharopolyspora spinosa Streptomyces fradiae

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Cellular differentiation and antibiotic production by Streptomyces nodosus immobilised in alginate capsules

In vitro polyketide biocatalysis : triketide building-blocks and enzymology