Abstract
BackgroundCholesterol oxidase biosensors have been used to determine the level of cholesterol in different serum and food samples. Due to a wide range of industrial and clinical applications of microbial cholesterol oxidase, isolation and identification of a new microbial source (s) of cholesterol oxidase are very important.ResultsThe local isolate Streptomyces sp. strain NEAE-94 is a promising source of cholesterol oxidase. It was identified based on cultural, morphological and physiological characteristics; in addition to the 16S rRNA sequence. The sequencing product had been deposited in the GenBank database under the accession number KC354803. Cholesterol oxidase production by Streptomyces anulatus strain NEAE-94 in shake flasks was optimized using surface response methodology. The different process parameters were first screened using a Plackett-Burman design and the parameters with significant effects on the production of cholesterol oxidase were identified. Out of the 15 factors screened, agitation speed, cholesterol and yeast extract concentrations had the most significant positive effects on the production of cholesterol oxidase. The optimal levels of these variables and the effects of their mutual interactions on cholesterol oxidase production were determined using Box-Behnken design. Cholesterol oxidase production by Streptomyces anulatus strain NEAE-94 was 11.03, 27.31 U/mL after Plackett-Burman Design and Box-Behnken design; respectively, with a fold of increase of 6.06 times compared to the production before applying the Plackett-Burman design (4.51 U/mL).ConclusionsMaximum cholesterol oxidase activity was obtained at the following fermentation conditions: g/L (cholesterol 4, yeast extract 5, NaCl 0.5, K2HPO4 1, FeSO4.7H2O 0.01, MgSO4.7H2O 0.5), pH 7, inoculum size 4% (v/v), temperature 37°C, agitation speed of 150 rpm, medium volume 50 mL and incubation time 5 days.
Highlights
Cholesterol oxidase biosensors have been used to determine the level of cholesterol in different serum and food samples
The objectives of this study were to identify robust cholesterol-assimilating actinomycetes strain with high cholesterol oxidase activity, and to optimize the fermentation conditions for enhanced production of cholesterol oxidase by Streptomyces anulatus strain NEAE-94 using response surface methodology
Actinomycete strain, Streptomyces sp. strain NEAE-94, has been tested for its cholesterol oxidase activity with a plate-based method, the formation of the pink areas around the colonies indicated the presence of cholesterol oxidase activity (Fig. 1)
Summary
Cholesterol oxidase biosensors have been used to determine the level of cholesterol in different serum and food samples. Cholesterol oxidase of microbial origin exhibits a wide range of industrial applications besides to its clinical applications in order to determine food and serum cholesterol levels which are important in the diagnosis of cardiovascular disease, atherosclerosis and other lipid disorders [2, 3]. It plays an essential role in macrophages and leukocytes lysis [4]. Cholesterol oxidase from Streptomyces natalensis is required for the biosynthesis of the polyene macrolide pimaricin (antifungal antibiotic) which is used as a mould inhibitor in the food industry [6] to prevent food contamination. It is used as an antibiotic effective in the treatment of keratitis because it interacts with the molecules of sterols present in fungal cell membranes which cause membrane disruption and leading to intracellular components leakage [7]
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