Abstract
To obtain chitinase-producing microorganisms with high chitinolytic activity at low temperature, samples collected from Fildes Peninsula in Antarctica were used as sources for bioprospecting of chitinolytic microorganisms. A cold-adapted strain, designated as GWSMS-1, was isolated from marine sediment and further characterized as Pseudomonas. To improve the chitinase production, one-factor-at-a-time and orthogonal test approaches were adopted to optimize the medium components and culture conditions. The results showed that the highest chitinolytic activity (6.36 times higher than that before optimization) was obtained with 95.41 U L−1 with 15 g L−1 of glucose, 1 g L−1 of peptone, 15 g L−1 of colloid chitin and 0.25 g L−1 of magnesium ions contained in the medium, cultivated under pH 7.0 and a temperature of 20 °C. To better understand the application potential of this strain, the enzymatic properties and the antifungal activity of the crude chitinase secreted by the strain were further investigated. The crude enzyme showed the maximum catalytic activity at 35 °C and pH 4.5, and it also exhibited excellent low-temperature activity, which still displayed more than 50% of its maximal activity at 0 °C. Furthermore, the crude chitinase showed significant inhibition of fungi Verticillium dahlia CICC 2534 and Fusarium oxysporum f. sp. cucumerinum CICC 2532, which can cause cotton wilt and cucumber blight, respectively, suggesting that strain GWSMS-1 could be a competitive candidate for biological control in agriculture, especially at low temperature.
Highlights
Chitin is a polysaccharide consisting of β-N-acetyl-d-glucosamine (GlcNAc) units linked by β-1,4 glycosidic bonds [1]
Strain GWSMS-1 was classified into genus Pseudomonas by molecular identification using 16SrDNA
Strain GWSMS-1 was classified into genus Pseudomonas by molecular identification using 16S-rDNA
Summary
Chitin is a polysaccharide consisting of β-N-acetyl-d-glucosamine (GlcNAc) units linked by β-1,4 glycosidic bonds [1]. Chitin can be decomposed through physical, chemical or biological approaches [3]. Physical and chemical methods have been used broadly, both of them have many invincible drawbacks such as low yield, high cost, poor product uniformity and environmental pollution, while a biological method possesses the advantages of mild reaction condition, good yield, high product uniformity and environmental friendliness, especially for the enzymatic method implemented by chitinase [4]. Chitinases, which are capable of hydrolyzing chitin to release GlcNAc and N-acetyl chitin oligosaccharides [5], have been found in many organisms, including bacteria [6], fungi [7], plants [8], Mar. Drugs 2019, 17, 695; doi:10.3390/md17120695 www.mdpi.com/journal/marinedrugs [11] and preparation of chitin derivatives [4] in recent years. Plenty of chitinase-producing microorganisms have been discovered and characterized, such as Sanguibacter antarcticus KOPRI
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