New lipase-producing Streptomyces isolated from halo-alkaline habitat in Wadi El Natrun: polyphasic identification and statistical optimization of enzyme production

Bioprospecting lipase producers in non-conventional habitats are the way to find special enzymes of diverse applications. Halo-alkaline marshes in Wadi El Natrun in Egypt are some of the most stable ecological systems in the world, and because of the double extremities of alkalinity and salinity, they harbor individual microbes capable of adapting stress conditions. Eight strains were recovered from the coastline soil of Al-Beida Lake in Wadi El Natrun and have been tested for lipase production. Among the eight isolates, the strain SBLWN_MH2 was the most active producer of lipase (7.5 U/ml). The crude SBLWN_MH2 lipase showed activity over a wide pH range (3.5 to 13) with an optimum pH at 10.5, and it was able to show more than 75% of its highest activity at pH elevated up to 13. The identification using phenotypic and genotypic methods strongly indicated that the strain SBLWN_MH2 belonged to the genus Streptomyces with a similarity of 99%. Thus, it has been given the suggested name Streptomyces sp. SBLWN_MH2 (MG593538). SBLWN_MH2 produced extracellular lipase in modified starch casein medium supplemented with different oils or Tween-80, and the potential production rate has been attained in the case of linseed oil after 3 days. Further experiments have been carried out to optimize medium composition through Box-Behnken design and response surface methodology, and it was possible to achieve more than 3.5-fold increase in lipase production. The present study indicates that Streptomyces sp. SBLWN_MH2 is a potential lipase producer and could be fruitfully employed in the large-scale production of highly alkaline lipase.