title: Quantification of the contribution of surface outgrowth to biocatalysis in sol-gels: oxytetracycline production by Streptomyces rimosus.
abstract: A technique was developed for differentiating the activity of microbes solely within sol gels by using the contribution of biomass outgrowth. Streptomyces rimosus was immobilised in colloidal silica gels and biomass growth, oxytetracycline synthesis, pH and carbohydrate consumption were compared for UV surface-sterilised gels, untreated gels, and liquid cultures. Absolute and biomass specific oxytetracycline yields were higher for non-sterile gels than for liquid culture. Biomass solely within colloidal silica gels (1.7 mg ml(-1)), and gels obtained from colloidal silica modified by addition of larger silica particles (1.2 mg ml(-1)) yielded 27 and 21 microg ml(-1) oxytetracycline compared with 97 and 104 microg ml(-1) for unsterilised gels (3.6 and 5.2 mg ml(-1) biomass) displaying outgrowth. It was therefore apparent that biomass and antibiotic production within the gels was limited and that optimisation requires gel modification.
authors.affiliation: Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, Sydney, Australia. apt@ansto.gov.au
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Taylor
authors.forename: Kim S
authors.initials: KS
authors.lastname: Finnie
authors.forename: John R
authors.initials: JR
authors.lastname: Bartlett
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Holden
mesh_terms: D019149:Bioreactors / Q000382:microbiology; D018929:Cell Culture Techniques / Q000379:methods*; D049109:Cell Proliferation; D006863:Hydrogen-Ion Concentration; D010118:Oxytetracycline / Q000096:biosynthesis*; D058428:Silica Gel; D012822:Silicon Dioxide / Q000737:chemistry* / Q000528:radiation effects*; D013242:Sterilization / Q000379:methods*; D013302:Streptomyces / Q000166:cytology* / Q000502:physiology*; D013499:Surface Properties; D014466:Ultraviolet Rays
chemical_list: D058428:Silica Gel; D012822:Silicon Dioxide; D010118:Oxytetracycline