Functional analysis of a novel lytic polysaccharide monooxygenase from Streptomyces griseus on cellulose and chitin

Identification of chitinase from Bacillus velezensis strain S161 and its antifungal activity against Penicillium digitatum

Previous studies have demonstrated the presence of chitinase in Bacillus velezensis through extensive genomic sequencing and experimental analyses. However, the detailed structure, functional roles, and antifungal activity of these chitinases remain poorly characterized. In this study, genomic screening identified three genes-chiA, chiB, and lpmo10-associated with chitinase degradation in B. velezensis S161. These genes encode chitinases ChiA and ChiB, and lytic polysaccharide monooxygenase LPMO10. Both ChiA and ChiB contain two CBM50 binding domains and one catalytic domain, whereas LPMO10 includes a signal peptide and a single catalytic domain. The chitinases ChiA, its truncated variant ChiA2, and ChiB were heterologously expressed in Escherichia coli. The purified enzymes efficiently degraded colloidal chitin and inhibited the spore germination of Penicillium digitatum. Notably, even after losing one CBM50 domain, the resultant enzyme, consisting of the remaining CBM50 domain and the catalytic domain, maintained its colloidal chitin hydrolysis and antifungal activity, indicating commendable stability. These results underscore the role of B. velezensis chitinases in suppressing plant pathogenic fungi and provide a solid foundation for developing and applying chitinase-based biocontrol strategies.

Heterologous Expression and Characterization of a pH-Stable Chitinase from Micromonospora aurantiaca with a Potential Application in Chitin Degradation

To promote the bioconversion of marine chitin waste into value-added products, we expressed a novel pH-stable Micromonospora aurantiaca-derived chitinase, MaChi1, in Escherichia coli and subsequently purified, characterized, and evaluated it for its chitin-converting capacity. Our results indicated that MaChi1 is of the glycoside hydrolase (GH) family 18 with a molecular weight of approximately 57 kDa, consisting of a GH18 catalytic domain and a cellulose-binding domain. We recorded its optimal activity at pH 5.0 and 55 °C. It exhibited excellent stability in a wide pH range of 3.0-10.0. Mg2+ (5 mM), and dithiothreitol (10 mM) significantly promoted MaChi1 activity. MaChi1 exhibited broad substrate specificity and hydrolyzed chitin, chitosan, cellulose, soluble starch, and N-acetyl chitooligosaccharides with polymerization degrees ranging from three to six. Moreover, MaChi1 exhibited an endo-type cleavage pattern, and it could efficiently convert colloidal chitin into N-acetyl-D-glucosamine (GlcNAc) and (GlcNAc)2 with yields of 227.2 and 505.9 mg/g chitin, respectively. Its high chitin-degrading capacity and exceptional pH tolerance makes it a promising tool with potential applications in chitin waste treatment and bioactive oligosaccharide production.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: An update for 2019-2020

This review is the tenth update of the original article published in 1999 on the application of matrix-assisted laser desorption/ionization (MALDI) mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2020. Also included are papers that describe methods appropriate to analysis by MALDI, such as sample preparation techniques, even though the ionization method is not MALDI. The review is basically divided into three sections: (1) general aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, fragmentation, quantification and the use of arrays. (2) Applications to various structural types such as oligo- and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals, and (3) other areas such as medicine, industrial processes and glycan synthesis where MALDI is extensively used. Much of the material relating to applications is presented in tabular form. The reported work shows increasing use of incorporation of new techniques such as ion mobility and the enormous impact that MALDI imaging is having. MALDI, although invented nearly 40 years ago is still an ideal technique for carbohydrate analysis and advancements in the technique and range of applications show little sign of diminishing.

Lytic polysaccharide monooxygenase - A new driving force for lignocellulosic biomass degradation

Lytic polysaccharide monooxygenases (LPMOs) can catalyze polysaccharides by oxidative cleavage of glycosidic bonds and have catalytic activity for cellulose, hemicellulose, chitin, starch and pectin, thus playing an important role in the biomass conversion of lignocellulose. The catalytic substrates of LPMOs are different and the specific catalytic mechanism has not been fully elucidated. Although there have been many studies related to LPMOs, few have actually been put into industrial biomass conversion, which poses a challenge for their expression, regulation and application. In this review, the origin, substrate specificity, structural features, and the relationship between structure and function of LPMOs are described. Additionally, the catalytic mechanism and electron donor of LPMOs and their heterologous expression and regulation are discussed. Finally, the synergistic degradation of biomass by LPMOs with other polysaccharide hydrolases is reviewed, and their current problems and future research directions are pointed out.

Heterologous expression and characterization of a novel lytic polysaccharide monooxygenase from Natrialbaceae archaeon and its application for chitin biodegradation

Lytic polysaccharide monooxygenases could enhance the enzymatic conversion of recalcitrant polysaccharides by glycoside hydrolases. This study reports the expression and identification of a novel AA10 LPMO from Natrialbaceae archaeon, named NaLPMO10A, as a C1 oxidizer of chitin. The optimal temperature and pH for NaLPMO10A activity were 40 °C and 9.0, respectively, and NaLPMO10A exhibited high thermostability and pH stability under alkaline conditions. NaLPMO10A was also highly tolerant and stable when treated with high concentration of metal ions (1 M). Moreover, metal ions (Na⁺, K⁺, Ca²⁺ and Mg²⁺) significantly promoted NaLPMO10A activity and improved the saccharification efficiency of chitin by 22.6%, 45.9%, 36.7% and 53.9%, respectively, compared to commercial chitinase alone. Together, the findings of this study fill a gap in archaeal LPMO research, and for the first time demonstrate that archaeal NaLPMO10A could be a promising enzyme for improving saccharification under extreme condition, with potential applications in biorefineries.

Harnessing microbial wealth for lignocellulose biomass valorization through secretomics: a review

The recalcitrance of lignocellulosic biomass is a major constraint to its high-value use at industrial scale. In nature, microbes play a crucial role in biomass degradation, nutrient recycling and ecosystem functioning. Therefore, the use of microbes is an attractive way to transform biomass to produce clean energy and high-value compounds. The microbial degradation of lignocelluloses is a complex process which is dependent upon multiple secreted enzymes and their synergistic activities. The availability of the cutting edge proteomics and highly sensitive mass spectrometry tools make possible for researchers to probe the secretome of microbes and microbial consortia grown on different lignocelluloses for the identification of hydrolytic enzymes of industrial interest and their substrate-dependent expression. This review summarizes the role of secretomics in identifying enzymes involved in lignocelluloses deconstruction, the development of enzyme cocktails and the construction of synthetic microbial consortia for biomass valorization, providing our perspectives to address the current challenges.