A novel finding that Streptomyces clavuligerus can produce the antibiotic clavulanic acid using olive oil as a sole carbon source.

AIMS: This study aims to establish whether commercially available food oils can be used by Streptomyces clavuligerus as sole carbon sources for growth and clavulanic acid production. METHODS AND RESULTS: Batch cultures in bioreactors showed that Strep. clavuligerus growth and clavulanic acid yields in a P-limited medium containing 0.6% (v/v) olive oil were respectively 2.5- and 2.6-fold higher than in a glycerol-containing medium used as control. Glycerol- and olive oil-grown cells present different macromolecular composition, particularly lipid and protein content. CONCLUSIONS: Streptomyces clavuligerus uses olive oil as the sole carbon and energy source for growth and clavulanic acid production. Yields and production rates in olive oil are comparable to those reported for oil-containing complex media. Differences in yields and in the macromolecular composition indicate that different metabolic pathways convert substrate into product. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first report of oils being used as the sole carbon source by Strep. clavuligerus. Apart from economic benefits, interesting questions are raised about Strep. clavuligerus physiology. Defined culture media allow physiological studies to be performed in the absence of interference by other compounds. Understanding how Strep. clavuligerus catabolises oils may have an economic impact in clavulanic acid production.

Characterization of the metabolic burden on Escherichia coli DH1 cells imposed by the presence of a plasmid containing a gene therapy sequence.

The presence of a plasmid, containing gene sequences for DNA immunotherapy that are not expressed in microbial culture, imposed a degradation in bioreactor performance in cultures of the host E. coli strain. Significant decreases in growth rate (24%) and biomass yield (7%) and a corresponding increase in overflow metabolism were observed in a strain containing a therapeutic sequence (a hepatitis B antigen under the control of a CMV promotor). The observed increase in overflow metabolism was incorporated into a Metabolic Flux Analysis (MFA) model (as acetate secretion). Metabolic flux analysis revealed an increase in TCA cycle flux, consistent with an increased respiration rate observed in plasmid-containing cells. These effects are thought to result from increased ATP synthesis requirements (24%) arising from the expression of the Kanr plasmid marker gene whose product accounted for 18% of the cell protein of the plasmid-containing strain. These factors will necessitate significantly higher aeration and agitation rates or lower nutrient feed rates in high-density cultures than would be expected for plasmid-free cultures.

Cyclic fed-batch culture for production of human serum albumin in Pichia pastoris.

Simple cyclic fed-batch culture (cfbc), consisting of a constant medium feed with periodic withdrawals of culture, resulted in a product yield (13.4 mg protein per gram biomass) similar to that obtained using the complex multiphase industrial production strategy (13.7 mg protein per gram biomass). In cfbc, productivity was ultimately limited by the rate at which the cells could assimilate methanol. Glycerol was inhibitory to growth at high concentrations. However, product yield continued to increase as the glycerol concentration was increased. In chemostat culture, dissolved oxygen concentration influenced product yield independently of any detectable influence on cell growth.

Organic and inorganic nitrogen source ratio effects onBacillus thuringiensis var.israelensis delta-endotoxin production.

The influence of different organic and inorganic nitrogen source combinations and C∶N ratios was studied in connection with growth and protein production ofBacillus thuringiensis var.israelensis. Protein production was assumed to be proportional to delta-endotoxin production. Delta-endotoxin concentration increased when media were supplemented with (NH4)2SO4, but the delta-endotoxin: biomass dry weight ratio was unaffected by different C∶N ratios. Organic nitrogen source, yeast extract, could be partially replaced by (NH4)2SO4 with a significant increase in delta-endotoxin production.