Expression and production of thermophilic alginate lyases in Bacillus and direct application of culture supernatant for seaweed saccharification

• Published in: Algal research (Amsterdam) Vol. 60; p. 102512
• Main Authors: Rhein-Knudsen, Nanna, Guan, Chengran, Mathiesen, Geir, Horn, Svein Jarle
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.12.2021
• Subjects: Alginate lyase; Bacillus; Macroalgae; Seaweed biorefining; Seaweed saccharification; Alginate lyase; Seaweed biorefining; Seaweed saccharification; Macroalgae; Bacillus
• ISSN: 2211-9264; 2211-9264
• DOI: 10.1016/j.algal.2021.102512

Brown seaweeds are rich in carbohydrates and may be used as a source of fermentable sugars. Saccharification of the seaweed biomass can be carried out enzymatically by a combination of cellulases and alginate lyases. In this study, thermotolerant exo- and endo alginate lyases were cloned and expressed in Bacillus subtilis. The lyases were secreted to the culture supernatant and used directly together with a commercial cellulase preparation to saccharify Saccharina latissima biomass. The results showed that the strategy of using the culture supernatants directly as a source of alginate lyases worked very well, releasing glucose, mannitol, and uronic acids. The ratio between the exo- and endo-acting alginate lyases proved to be very important for saccharification yield, and under optimal reaction conditions the use of culture supernatants containing alginate lyases improved final glucose concentration by 73%, when compared to only applying cellulases. This direct use of culture supernatants as a source of alginate lyases shows that enzyme purification steps are not needed, saving seaweed processing costs and points to the possibility of a relatively simple on-site enzyme production for seaweed biorefining. •Thermotolerant exo- and endo alginate lyases can be expressed in Bacillus subtilis.•Culture supernatants can be used directly as a source of enzymes.•Alginate lyases improve glucose yields up to 73% compared to only using cellulases.•The ratio between exo- and endo alginate lyases affects saccharification yield.