Abstract
Pleurotus ostreatus is a species of white-rot fungi that effectively degrades lignin. In this study, we aimed to efficiently express the lac-2 gene of Pleurotus ostreatus in the Pichia pastoris X33 yeast strain. The enzymatic properties of recombinant yeast were determined, and its ability to degrade corn stover lignin was determined. The results showed the optimum pH values of recombinant laccase for 2,2’-Azinobis-3-ethylbenzothiazoline-6-sulfonic acid, 2,6-dimethoxyphenol, and 2-methoxyphenol were 3.0, 3.0, and 3.5, respectively. The optimum reaction temperature was 50 °C, and it had good thermal stability and acid and alkali resistance. The degradation rate of lignin in corn stover by recombinant laccase was 18.36%, and the native Pleurotus ostreatus degradation rate was 14.05%, the difference between them is significant (p < 0.05). This experiment lays a foundation for the study of the degradation mechanism of lignin by laccase.
Highlights
Laccases (EC 1.10.3.2) are polyphenol copper blue proteases containing four copper ions and exist in plants, fungi, insects, and a small number of bacteria [1,2,3,4,5]
Laccase can degrade the complex structure of lignin that makes up the cell wall of stover, which makes it an excellent candidate to biodegrade renewable biological resources for reuse
The white-rot fungus strain Pleurotus ostreatus was provided by the microorganism of Heilongjiang Province and cultured on potato dextrose Agar (PDA) medium at 25 ◦C
Summary
Laccases (EC 1.10.3.2) are polyphenol copper blue proteases containing four copper ions (except Phlebia radiata laccase, which has two copper ions) and exist in plants, fungi, insects, and a small number of bacteria [1,2,3,4,5]. It has been found that the application value of laccase is very high, as it can be used for paper bleaching, medical and health purposes, as bio-fertilizer, and to degrade stubborn pollutants. Among these uses, the degradation of environmental pollutants by laccase has been widely studied [13,14]. White-rot fungi have been widely studied as one of the most effective producers of fungal laccase; So far, the heterologous expression of most laccases has been successful, for example, laccase genes have been cloned from Fome lignosus [17], Pycnoporus cinnabarinus [18], and various Trametes strains [19,20,21]. Recombinant laccase was used to degrade lignin, and the its ability was determined from qualitative and quantitative methods, which were not available in previous studies; 2) in the previous research on the degradation of lignin, the most studied was woody lignin, such as the research of Wei [24], Liu [25], etc., in this study, herbal lignin was used as the research object, to explore the effect of recombinant laccase on the degradability of herbal lignin
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