Characterization of a bifunctional alginate lyase as a new member of the polysaccharide lyase family 17 from a marine strain BP-2

Guiyuan Huang,Siming Liao,Shihan Pan,Jie Feng,Shushi Huang,Qiaozhen Wang,Shunhua Wen,Fu Lei,Rongcan Zhang,Wei Liao

doi:10.1007/s10529-019-02722-1

Abstract

ObjectivesBifunctional alginate lyase can efficiently saccharify alginate biomass and prepare functional oligosaccharides of alginate.ResultsA new BP-2 strain that produces alginate lyase was screened and identified from rotted Sargassum. A new alginate lyase, Alg17B, belonging to the polysaccharide lyase family 17, was isolated and purified from BP-2 fermentation broth by freeze-drying, dialysis, and ion exchange chromatography. The enzymatic properties of the purified lyase were investigated. The molecular weight of Alg17B was approximately 77 kDa, its optimum reaction temperature was 40–45 °C, and its optimum reaction pH was 7.5–8.0. The enzyme was relatively stable at pH 7.0–8.0, with a temperature range of 25–35 °C, and the specific activity of the purified enzyme reached 4036 U/mg. A low Na+ concentration stimulated Alg17B enzyme activity, but Ca2+, Zn2+, and other metal ions inhibited it. Substrate specificity analysis, thin-layer chromatography, and mass spectrometry showed that Alg17B is an alginate lyase that catalyses the hydrolysis of sodium alginate, polymannuronic acid (polyM) and polyguluronic acid to produce monosaccharides and low molecular weight oligosaccharides. Alg17B is also bifunctional, exhibiting both endolytic and exolytic activities toward alginate, and has a wide substrate utilization range with a preference for polyM.ConclusionsAlg17B can be used to saccharify the main carbohydrate, alginate, in the ethanolic production of brown algae fuel as well as in preparing and researching oligosaccharides.

Highlights

Using brown algae as a biomass feedstock to produce third-generation fuels has attracted public and scientific attention in recent years (Enquist-Newman et al 2014; Ji et al 2016; John et al 2011)
Strain BP-2 producing the alginate lyase with the highest activity was screened from 24 isolates using alginate as the sole carbon source
MEGA 5.1 (Xu et al 2014) was used to construct a phylogenetic tree using the neighbourjoining (NJ) method (Fig. 1), and the results showed that the BP-2 strain was on an independent evolutionary branch

Summary

Introduction

Using brown algae as a biomass feedstock to produce third-generation fuels has attracted public and scientific attention in recent years (Enquist-Newman et al 2014; Ji et al 2016; John et al 2011). Using brown algae as feedstock for biofuels does not face the same food issues as land-based biomass production (John et al 2011; Jang et al 2012; Kim et al 2011). Converting the main polysaccharide constituents in brown algae into bioethanol is more competitive than producing ethanol derived from terrestrial plants. This approach is one potential means of solving the energy crisis and future environmental problems (Enquist-Newman et al 2014; Ji et al 2016; Wargacki et al 2012). Alginate is the most abundant polysaccharide in marine organisms and is the world’s second most abundant biopolymer after cellulose; mannitol is ranked second in algal carbohydrates, with a content of 20% (w/w) in some brown algae (Ji et al 2016)

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