Recent progress on engineering microbial alginate lyases towards their versatile role in biotechnological applications

Abstract

Biomass feedstock is an efficient and harmless source of energy. There are various sources of feedstock, such as plant, microbial, macro, and microalgae, and agricultural waste. The major component in biomass feedstock material is a polysaccharide, such as cellulose, cellobiose, starch, and alginate. Alginate is mainly found in macroalgae as one of the significant polysaccharide components. It is made up of β-d-mannuronate (M) and α-l-guluronate (G) blocks. Alginate lyase is an enzyme that degrades alginate by breaking the glycosidic linkage between the poly M and G blocks to liberate oligosaccharides. Several organisms, including bacteria, fungi, viruses, and algae can produce alginate lyases. The species of bacteria, such as Bacillus, Vibrio, Pseudomonas, and Microbulbifer, are some of the important sources of alginate lyases. They are industrially essential enzymes used in food, biofuel, and biomedical industries. There are various assays available to determine the alginate lyase activity qualitatively as well as quantitatively. Qualitatively, different dyes like Gram's iodine, cetyl pyridinium chloride, and rutanium red can be used to visualize the zone formed due to the alginate lyase activity. DNS assay, UV absorption, and the Somogyi-Nelson method help to determine the alginate lyase activity quantitatively. Since the alginate lyase production in the native organisms is relatively lower, the genes encoding alginate lyases are heterologously cloned and expressed in E. coli to maximize the production and to characterize the enzyme. Different chromatographic techniques like size exclusion, affinity, gel permeation, and ion-exchange chromatography are used to purify the protein. In this paper, the source of alginate and alginate lyases, the mechanism of action of the enzyme, the engineering approaches to enhance the enzyme production, its purification strategy, and the potential applications of alginate lyases has been discussed.