Isolation and identification of two novel SDS-resistant secreted chitinases from Aeromonas schubertii

Function analysis and characterisation of a novel chitinase, MdCht9, in Musca domestica

Insect chitinases have been proposed as potential targets for pest control. In this work, a novel group IV chitinase gene, MdCht9, from Musca domestica was found to have multiple functions in the physiological activity, including chitin regulation, development and antifungal immunity. The MdCht9 gene was cloned and sequenced, its phylogeny was analysed and its expression was determined in normal and 20E treated larvae. Subsequently, RNA interference (RNAi)-mediated MdCht9 knockdown was performed, followed by biochemical assays, morphological observations and transcriptome analysis. Finally, the recombinant protein MdCht9 (rMdCht9) was purified and tested for anti-microbial activity and enzyme characteristics. The results showed that MdCht9 consists of three domains, highly expressed in a larval salivary gland. RNAi silencing of MdCht9 resulted in significant down-regulation of chitin content and expression of 15 chitin-binding protein (CBP) genes, implying a new insight that MdCht9 might regulate chitin content by influencing the expression of CBPs. In addition, more than half of the lethality and partial wing deformity appeared due to the dsMdCht9 treatment. In addition, the rMdCht9 exhibited anti-microbial activity towards Candida albicans (fungus) but not towards Escherichia coli (G-) or Staphylococcus aureus (G+). Our work expands on previous studies of chitinase while providing a potential target for pest management.

Microbial production of N-acetyl-D-glucosamine (GlcNAc) for versatile applications: Biotechnological strategies for green process development

N-acetyl-d-glucosamine (GlcNAc) is a commercially important amino sugar for its wide range of applications in pharmaceutical, food, cosmetics and biofuel industries. In nature, GlcNAc is polymerised into chitin biopolymer, which is one of the major constituents of fungal cell wall and outer shells of crustaceans. Sea food processing industries generate a large volume of chitin as biopolymeric waste. Because of its high abundance, chitinaceous shellfish wastes have been exploited as one of the major precursor substrates of GlcNAc production, both in chemical and enzymatic means. Nevertheless, the current process of GlcNAc extraction from shellfish wastes generates poor turnover and attracts environmental hazards. Moreover, GlcNAc isolated from shellfish could not be prescribed to certain groups of people because of the allergic nature of shell components. Therefore, an alternative route of GlcNAc production is advocated. With the advancement of metabolic construction and synthetic biology, microbial synthesis of GlcNAc is gaining much attention nowadays. Several new and cutting-edge technologies like substrate co-utilization strategy, promoter engineering, and CRISPR interference system were proposed in this fascinating area. The study would put forward the potential application of microbial engineering in the production of important pharmaceuticals. Very recently, autotrophic fermentation of GlcNAc synthesis has been proposed. The metabolic engineering approaches would offer great promise to mitigate the issues of low yield and high production cost, which are major challenges in microbial bio-processes industries. Further process optimization, optimising metabolic flux, and efficient recovery of GlcNAc from culture broth, should be investigated in order to achieve a high product titer. The current study presents a comprehensive review on microbe-based eco-friendly green methods that would pave the way towards the development of future research directions in this field for the designing of a cost-effective fermentation process on an industrial setup.

Microbial chitinases and their relevance in various industries

Chitin, the second most abundant biopolymer on earth after cellulose, is composed of β-1,4-N-acetylglucosamine (GlcNAc) units. It is widely distributed in nature, especially as a structural polysaccharide in the cell walls of fungi, the exoskeletons of crustaceans, insects, and nematodes. However, the principal commercial source of chitin is the shells of marine or freshwater invertebrates. Microbial chitinases are largely responsible for chitin breakdown in nature, and they play an important role in the ecosystem's carbon and nitrogen balance. Several microbial chitinases have been characterized and are gaining prominence for their applications in various sectors. The current review focuses on chitinases of microbial origin, their diversity, and their characteristics. The applications of chitinases in several industries such as agriculture, food, the environment, and pharmaceutical sectors are also highlighted.

Purification, characterization and cloning of a chitinase from Stenotrophomonas rhizophila G22

In the presented research the extracellular chitinase of Stenotrophomonas rhizophila G22 was biochemically and molecularly characterized. The studied enzyme was purified from a 72-h bacterial culture about 14 times, with a recovery of 63%. The molecular weight of the purified protein was estimated at 50 kDa by SDS-PAGE. The enzyme showed high activity against colloidal chitin. Significantly lower activities were observed with native chitin powder and chitosan. Adsorption of the enzyme to colloidal chitin and to powdered chitin at the level of 75% and 37%, respectively, was observed after 30 min of reaction. Optimum temperature and pH were 37 °C and 5.9, respectively. The enzyme demonstrated higher activity against nitrophenyl-β d N, N', N″-triacetylchitotriose and approx. 5 times lower activity for 4-nitrophenyl-N, N'-diacetyl-β-d-chitobiose. The enzyme is an endochitinase, which is confirmed by the K _m and V _max values determined in the studies. S. rhizophila G22 endochitinase was inhibited in the presence of cysteine-specific inhibitors, which indicates the role of cysteine moieties in the mechanism of catalysis or in stabilisation of the enzyme molecule. Also Ca²⁺ and Mn²⁺ ions may stabilise the protein's spatial structure. SDS and ions: Fe²⁺, Cu²⁺, Co²⁺, Zn²⁺ inhibited the activity of enzyme. A full-length (2109 bp) gene coding chitinase from S. rhizophila G22 was obtained. Four domains typical for glycoside hydrolase family 18 (GH 18) chitinases were identified: catalytic Gly_18, chitin-binding-ChtBD3, type-III fibronectin-FN3 and polycystic kidney disease domain-PKD domain.

Antifungal performance of extracellular chitinases and culture supernatants of Streptomyces galilaeus CFFSUR-B12 against Mycosphaerella fijiensis Morelet

The tropical and mycoparasite strain Streptomyces galilaeus CFFSUR-B12 was evaluated as an antagonist of Mycosphaerella fijiensis Morelet, causal agent of the Black Sigatoka Disease (BSD) of banana. On zymograms of CFFSUR-B12 culture supernatants, we detected four chitinases of approximately 32 kDa (Chi32), 20 kDa (Chi20), and two with masses well over 170 kDa (ChiU) that showed little migration during denaturing electrophoresis at different concentrations of polyacrylamide. The thymol-sulphuric acid assay showed that the ChiU were glycosylated chitinases. Moreover, matrix assisted laser desorption ionization time-of-flight MS analysis revealed that the ChiU are the same protein and identical to a family 18 chitinase from Streptomyces sp. S4 (gi|498328075). Chi32 was similar to an extracellular protein from Streptomyces albus J1074 (gi|478687481) and Chi20 was non-significantly similar to chitinases from five different strains of Streptomyces (P > 0.05). Subsequently, Chi32 and Chi20 were partially purified by anion exchange and hydrophobic interaction chromatography and tested against M. fijiensis. Chitinases failed to inhibit ascospore germination, but inhibited up to 35 and 62% of germ tube elongation and mycelial growth, respectively. We found that crude culture supernatant and living cells of S. galilaeus CFFSUR-B12 were the most effective in inhibiting M. fijiensis and are potential biocontrol agents of BSD.

Purification and characterization of a novel chitinase from Trichosanthes dioica seed with antifungal activity

Chitinases are a group of enzymes that show differences in their molecular structure, substrate specificity, and catalytic mechanism and widely found in organisms like bacteria, yeasts, fungi, arthropods actinomycetes, plants and humans. A novel chitinase enzyme (designated as TDSC) was purified from Trichosanthes dioica seed with a molecular mass of 39±1 kDa in the presence and absence of β-mercaptoethanol. The enzyme was a glycoprotein in nature containing 8% neutral sugar. The N-terminal sequence was determined to be EINGGGA which did not match with other proteins. Amino acid analysis performed by LC-MS revealed that the protein was rich in leucine. The enzyme was stable at a wide range of pH (5.0-11.0) and temperature (30-90 °C). Chitinase activity was little bit inhibited in the presence of chelating agent EDTA (ethylenediaminetetraaceticacid), urea and Ca(2+). A strong fluorescence quenching effect was found when dithiothreitol and sodium dodecyl sulfate were added to the enzyme. TDSC showed antifungal activity against Aspergillus niger and Trichoderma sp. as tested by MTT assay and disc diffusion method.

Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry: an update for 2009-2010

This review is the sixth update of the original article published in 1999 on the application of MALDI mass spectrometry to the analysis of carbohydrates and glycoconjugates and brings coverage of the literature to the end of 2010. General aspects such as theory of the MALDI process, matrices, derivatization, MALDI imaging, arrays and fragmentation are covered in the first part of the review and applications to various structural typed constitutes the remainder. The main groups of compound that are discussed in this section are oligo and polysaccharides, glycoproteins, glycolipids, glycosides and biopharmaceuticals. Many of these applications are presented in tabular form. Also discussed are medical and industrial applications of the technique, studies of enzyme reactions and applications to chemical synthesis.

Purification and properties of a Meloidogyne-antagonistic chitinase from Lysobacter capsici YS1215

The root-knot nematodes, Meloidogyne spp., cause serious diseases in various plants and their chemical control may lead to environmental problems. Therefore, alternative control measures against the phytopathogenic nematodes are being sought. One of the potential targets against Meloidogyne spp. may be the chitinolysis and degradation of nematode eggs. Therefore, in the present study, a chitinolytic and nematicidal strain of Lysobacter capsici YS1215 was isolated from an agricultural field in Korea. The aim of this study was to purify chitinase secreted by L. capsici YS1215 and investigate its nematicidal role against Meloidogyne incognita. The chitinase secreted by L. capsici YS1215 was purified by protein precipitation with 80% ammonium sulphate, anion-exchange chromatography with DEAE-cellulose and gel-filtration chromatography with Sephadex G-100. By chitinase-active staining of the purified enzyme, a single band was obtained with an estimated molecular mass of 43.6 kDa. The optimal pH and optimal temperature for the highest chitinase activity were 6.0 and 40°C, respectively. The purified chitinase degraded the chitin layer of the eggshells and significantly reduced hatch of second-stage juveniles. The activity of chitinase secreted by L. capsici YS1215 was not affected by CoCl2, MnCl2, MgCl2, CuSO4, CaCl2 or EDTA. The purified enzyme could also hydrolyse swollen chitin, glycol chitin, glycol chitosan and chitin powder. Thus, the role of chitinase secreted by L. capsici YS1215 against Meloidogyne spp. may be useful for further development of a biocontrol agent.

Optimization of recombinant hexaoligochitin-producing chitinase production with response surface methodology

Hexaoligochitin produced by chitinase, ASCHI61, from Aeromonas schubertii was recently expressed. In this work, the optimal conditions for the mass production of ASCHI61 were investigated. The efficiency of recombinant protein expression in Escherichia coli was determined by various parameters, including the pH of the culture medium, induction temperature, shaking speed, inducer concentration, and induction period. The optimization experiments could be simplified through a statistical design of experiments (response surface methodology). From the fractional factorial design, the interactive effect of induction temperature and time was the most significant. The total activity of the enzyme was 32,092 U at 23.9 °C with 115 min of induction. Under those conditions, the total activity of the recombinant protein was 30,650 U in the fermentation experiments, with an error of only 4.8%. The total activity of ASCHI61 increased 1.54-fold under the optimal conditions. Based on the results, ASCHI61 can be expressed more for hexaoligochitin production.

A novel neutral xylanase with high SDS resistance from Volvariella volvacea: characterization and its synergistic hydrolysis of wheat bran with acetyl xylan esterase

A neutral xylanase (XynII) from Volvariella volvacea was identified and characterized. Unlike other modular xylanases, it consists of only a single GH10 catalytic domain with a unique C-terminal sequence (W-R-W-F) and a phenylalanine and proline-rich motif (T-P-F-P-P-F) at N-terminus, indicating that it is a novel GH10 xylanase. XynII exhibited optimal activity at pH 7 and 60 °C and stability over a broad range of pH 4.0–10.0. XynII displayed extreme highly SDS resistance retaining 101.98, 92.99, and 69.84 % activity at the presence of 300 mM SDS on birchwood, soluble oat spelt, and beechwood xylan, respectively. It remained largely intact after 24 h of incubation with proteinase K at a protease to protein ratio of 1:50 at 37 °C. The kinetic constants K  m value towards beechwood xylan was 0.548 mg ml−1, and the k  cat/K  m ratio, reflecting the catalytic efficiency of the enzyme, was 126.42 ml mg−1 s−1 at 60 °C. XynII was a true endo-acting xylanase lacking cellulase activity. It has weak activity towards xylotriose but efficiently hydrolyzed xylans and xylooligosaccharides larger than xylotriose mainly to xylobiose. Synergistic action with acetyl xylan esterase (AXEI) from V. volvacea was observed for de-starched wheat bran. The highest degree of synergy (DS 1.42) was obtained in sequential reactions with AXEI digestion preceding XynII. The high SDS resistance and intrinsic stability suggested XynII may have potential applications in various industrial processes especially for the detergent and textile industries and animal feed industries.

The identification and characterization of chitotriosidase activity in pancreatin from porcine pancreas

The versatile oligosaccharide biopolymers, chitin and chitosan, are typically produced using enzymatic processes. However, these processes are usually costly because chitinases and chitosanases are available in limited quantities. Fortunately, a number of commercial enzymes can hydrolyze chitin and chitosan to produce long chain chitin or chitosan oligosaccharides. Here, a platform to screen for enzymes with chitinase and chitosanase activities using a single gel with glycol chitin or glycol chitosan as a substrate was applied. SDS-resistant chitinase and chitosanase activities were observed for pancreatin. Its chitotriosidase had an optimal hydrolysis pH of 4 in the substrate specificity assay. This activity was thermally unstable, but independent of 2-mercaptoethanol. This is the first time a chitotriosidase has been identified in the hog. This finding suggests that oligochitosaccharides can be mass-produced inexpensively using pancreatin.

Chitosan, the marine functional food, is a potent adsorbent of humic acid

Chitosan is prepared by the deacetylation of chitin, the second-most abundant biopolymer in nature, and has applicability in the removal of dyes, heavy metals and radioactive waste for pollution control. In weight-reduction remedies, chitosan is used to form hydrogels with lipids and to depress the intestinal absorption of lipids. In this study, an experimental method was implemented to simulate the effect of chitosan on the adsorption of humic acid in the gastrointestinal tract. The adsorption capacity of chitosan was measured by its adsorption isotherm and analyzed using the Langmuir equation. The results showed that 3.3 grams of humic acid was absorbed by 1 gram of chitosan. The adsorption capacity of chitosan was much greater than that of chitin, diethylaminoethyl-cellulose or activated charcoal. Cellulose and carboxymethyl-cellulose, a cellulose derivative with a negative charge, could not adsorb humic acid in the gastrointestinal tract. This result suggests that chitosan entraps humic acid because of its positive charge.

N-acetyl glucosamine obtained from chitin by chitin degrading factors in Chitinbacter tainanesis

A novel chitin-degrading aerobe, Chitinibacter tainanensis, was isolated from a soil sample from southern Taiwan, and was proved to produce N-acetyl glucosamine (NAG). Chitin degrading factors (CDFs) were proposed to be the critical factors to degrade chitin in this work. When C. tainanensis was incubated with chitin, CDFs were induced and chitin was converted to NAG. CDFs were found to be located on the surface of C. tainanensis. N-Acetylglucosaminidase (NAGase) and endochitinase activities were found in the debris, and the activity of NAGase was much higher than that of endochitinase. The optimum pH of the enzymatic activity was about 7.0, while that of NAG production by the debris was 5.3. These results suggested that some factors in the debris, in addition to NAGase and endochitinase, were crucial for chitin degradation.

N-acetylglucosamine: production and applications

N-Acetylglucosamine (GlcNAc) is a monosaccharide that usually polymerizes linearly through (1,4)-β-linkages. GlcNAc is the monomeric unit of the polymer chitin, the second most abundant carbohydrate after cellulose. In addition to serving as a component of this homogeneous polysaccharide, GlcNAc is also a basic component of hyaluronic acid and keratin sulfate on the cell surface. In this review, we discuss the industrial production of GlcNAc, using chitin as a substrate, by chemical, enzymatic and biotransformation methods. Also, newly developed methods to obtain GlcNAc using glucose as a substrate in genetically modified microorganisms are introduced. Moreover, GlcNAc has generated interest not only as an underutilized resource but also as a new functional material with high potential in various fields. Here we also take a closer look at the current applications of GlcNAc, and several new and cutting edge approaches in this fascinating area are thoroughly discussed.

Colloid chitin azure is a dispersible, low-cost substrate for chitinase measurements in a sensitive, fast, reproducible assay

Chitin and its derivatives are widely used as biomedical materials because of their versatility and biocompatibility. Chitinases are enzymes that produce chito-oligosaccharides from chitin. The assay of chitinase activity is difficult because few appropriate substrates are available. In this study, the authors developed an efficient and low-cost chitinase assay using colloidal chitin azure. The assay feasibility is evaluated and compared with traditional assays employing colloidal chitin and chitin azure. The authors found that the optimum pH for determining chitinase activity using colloid chitin azure was pH 5 or 8. The method was sensitive, and the assay was complete within 30 min. When the assay was used to measure chitinase activities produced by 2 strains of chitinolytic bacteria, BCTS (an Escherichia coli BL21 [DE3] expressing a secretory recombinant chitinase) and AS1 (a chitinolytic bacterium with low levels of chitinase), it was shown that cultivation in Bushnell-Haas selection medium caused AS1 to secrete a higher level of chitinase than was secreted when the bacterium grew in other media. In summary, colloid chitin azure is a sensitive, feasible, reproducible, and low-cost substrate for the assay of chitinase activity.