Identification of cholesterol-assimilating actinomycetes strain and application of statistical modeling approaches for improvement of cholesterol oxidase production by Streptomyces anulatus strain NEAE-94

Abstract

Background: Cholesterol 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. Results: The 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 fifteen 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). Conclusions: Maximum cholesterol oxidase activity is obtained at the following fermentation conditions: g/L (cholesterol 4, yeast extract 5, NaCl 0.5, K 2 HPO 4 1, FeSO 4 .7H 2 O 0.01, MgSO 4 .7H 2 O 0.5), pH 7, inoculum size 4 % (v/v), temperature 37°C, agitation speed 150 rpm, medium volume 50 mL and incubation time 5 days.

Determination of In vitro lethality of actinomycetes antibiotic extracts from Menengai crater geothermal vents, Kenya

“…The results indicated that PAN 18 and PAN 117 caused partial hemolysis while PAN 9 and PAN 138 led to complete hemolysis of sheep blood erythrocytes. This concurred with previous studies carried out elsewhere El-Naggar and El-Shweihy, 2020). Blood erythrocytes bioassay is extremely sensitive to a wide range of antibiotic extracts from actinomycetes (Soyer and Tanul, 2020).…”