Gellan oligosaccharide can be degraded from gellan gum, and which has many biological functions such as prebiotic activity, plant induced disease resistance and so on. This study focused on the heterologous expression of gellan lyase by constructing recombinant Pichia pastoris and applied to the preparation of gellan oligosaccharide. After screening and identification, the recombinant strain of P. pastoris GS115-pPIC9K-nGL1 was first induced to express the gellan lyase at shake flask level, and the highest enzyme activity was 266.4 U/L; then, high-density fermentation was carried out in a 7 L bioreactor, and the enzyme activity reached 954.6 U/L, which was 3.58 times higher than that of shaking flask. The enzymatic properties were studied after the recombinant gellan lyase was isolated and purified. The analysis results indicated that the optimal temperature and pH of hydrolysis reaction were 45 ℃ and 7.5. The activity of gellan lyase was relatively stable at 45-50 ℃, pH 7.0-9.0, and it was slightly enhanced by Zn2+. In addition, Al3+ had a strong inhibitory effect on enzymatic reaction. The degradation product was analyzed by thin-layer chromatography combining with matrix-assisted laser analysis ionization time-of-flight mass spectrometry, the result showed that the polymerization degree of gellan oligosaccharide was 4. The gellan lyase derived from Bacillus sp. GL1 was heterologous expressed in P. pastoris GS115 for the first time, and the specific degradation of gellan gum to produce gellan oligosaccharide may have certain potential in industrial applications.
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