Abstract
There has been a recent increase in the exploration of cold-active β-galactosidases, as it offers new alternatives for the dairy industry, mainly in response to the current needs of lactose-intolerant consumers. Since extremophilic microbial compounds might have unique physical and chemical properties, this research aimed to study the capacity of Antarctic bacterial strains to produce cold-active β-galactosidases. A screening revealed 81 out of 304 strains with β-galactosidase activity. The strain Se8.10.12 showed the highest enzymatic activity. Morphological, biochemical, and molecular characterization based on whole-genome sequencing confirmed it as the first Rahnella inusitata isolate from the Antarctic, which retained 41–62% of its β-galactosidase activity in the cold (4 °C–15 °C). Three β-galactosidases genes were found in the R. inusitata genome, which belong to the glycoside hydrolase families GH2 (LacZ and EbgA) and GH42 (BglY). Based on molecular docking, some of these enzymes exhibited higher lactose predicted affinity than the commercial control enzyme from Aspergillus oryzae. Hence, this work reports a new Rahnella inusitata strain from the Antarctic continent as a prominent cold-active β-galactosidase producer.
Highlights
IntroductionAntarctica is possibly one of the most hostile habitats on Earth
Screenings based on cleaved X-Gal in agar plates revealed that 56% of Arctic bacteria were capable of milk degradation, and 40% of the Pseudoalteromonas sp. strains showed β-galactosidase activity [24]
New β-galactosidase alternatives with activity in cold and wide-range thermostability are currently needed in the glycoside hydrolases industry, for the preparation of lactose-free dairy products
Summary
Antarctica is possibly one of the most hostile habitats on Earth. It can be defined as a polyextreme environment, given the multiple harsh conditions for life, such as low temperatures, low humidity, limited bioavailability of water, high solar radiation intervals, extended periods of darkness, and freeze–thaw cycles [1]. Various organisms, mainly microorganisms, have adapted to colonize and proliferate under these extreme conditions and are of great interest as a source of novel bioactive biotechnological compounds [2,3]. There has been a great interest in discovering new enzymes from extremophilic microorganisms, called extremozymes, for industrial purposes [4]
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