Overexpression, purification and characterization of the Trichoderma atroviride endochitinase, Ech42, in Pichia pastoris

A novel antifungal chitinase from Chaetomium globosum: column-free purification and characterization

A new chitinase gene, cloned from the biocontrol Chaetomium globosum W7, was designated Cgchi18. Recombinant protein Cgchi18 with 535 amino acids was expressed in Escherichia coli, and purified by means of a column-free purification method relying on split intein, achieving a 12.39-fold purification and a 15.61% recovery yield. The maximum activity of this approximately 60-kDa protein was observed at 45 °C and pH 5.0. Cgchi18 was activated by Mg2+ and Ba2+, but inhibited by Mn2+, Co2+, Cu2+, Zn2+, Ag+ and Hg2+. Cgchi18 showed high substrate specificity, only hydrolyzing β-1,4-glycoside bond in chitin and its derivatives, to liberate disaccharides or trisaccharides. For the degradation of colloidal chitin under optimal conditions, Vmax and Km of Cgchi18 were calculated as 8.05 μmol/min/mg and 3.18 mg/mL, respectively. Additionally, it exhibited antifungal activity and could have a degrading effect on the spread of hyphae of pathogenic fungi. In conclusion, the chitinase Cgchi18 identified from C. globosum has potential for industrial and agricultural applications.

Recombinant expression and characterization of the endochitinase Chit36-TA from Trichoderma asperellum in Komagataella phaffii for chitin degradation of black soldier fly exuviae

The natural polymer chitin is an abundant source for valuable N-acetylchitooligosaccharides and N-acetylglucosamine applicable in several industries. The endochitinase Chit36-TA from Trichoderma asperellum was recombinantly expressed in Komagataella phaffii for the enzymatic degradation of chitin from unused insect exuviae into N-acetylchitooligosaccharides. Chit36-TA was purified by Ni-NTA affinity chromatography and subsequently biochemically characterized. After deglycosylation, the endochitinase had a molecular weight of 36 kDa. The optimum pH for Chit36-TA was 4.5. The temperature maximum of Chit36-TA was determined to be 50 °C, while it maintained > 93% activity up to 60 °C. The chitinase was thermostable up to 45 °C and exhibited ~ 50% activity after a 15 min incubation at 57 °C. Chit36-TA had a maximum specific enzyme activity of 50 nkat/mg with a Km value of 289 µM with 4-methylumbelliferyl-N,N',N″-triacetyl-β-chitotrioside as substrate. Most tested cations, organic solvents and reagents were well-tolerated by the endochitinase, except for SDS (1 mM), Cu2+ (10 mM) and Mn2+ (10 mM), which had stronger inhibitory effects with residual activities of 3, 41 and 28%, respectively. With a degree of hydrolysis of 32% applying colloidal shrimp chitin (1% (w/v)) and 12% on insect larvae (1% (w/v)) after 24 h, the endochitinase was found to be suitable for the conversion of colloidal chitin as well as chitin from black soldier fly larvae into water-soluble N-acetylchitooligosaccharides. To prove scalability, a bioreactor process was developed in which a 55-fold higher enzyme activity of 49 µkat/l and a tenfold higher protein expression of 1258 mg/l were achieved.

An overview of fungal chitinases and their potential applications

Chitin, the world's second most abundant biopolymer after cellulose, is composed of β-1,4-N-acetylglucosamine (GlcNAc) residues. It is the key structural component of many organisms, including crustaceans, mollusks, marine invertebrates, algae, fungi, insects, and nematodes. There has been a significant increase in the generation of chitinous waste from seafood businesses, resulting in a big amount of scrap. Although several organisms, such as plants, crustaceans, insects, nematodes, and animals, produce chitinases, microorganisms are promising candidates and a sustainable option that mediates chitin degradation. Fungi are the dominant group of chitinase producers among microorganisms. In fungi, chitinases are involved in morphogenesis, cell division, autolysis, chitin acquisition for nutritional purposes, and mycoparasitism. Many efficient chitinolytic fungi with potential applications have been identified in a variety of environments, including soil, water, marine wastes, and plants. The current review highlights the key sources of chitinolytic fungi and the characterization of fungal chitinases. It also discusses the applications of fungal chitinases and the cloning of fungal chitinase genes.

Biochemical Properties of a Cold-Active Chitinase from Marine Trichoderma gamsii R1 and Its Application to Preparation of Chitin Oligosaccharides

The enzymatic degradation of different chitin polymers into chitin oligosaccharides (COSs) is of great significance given their better solubility and various biological applications. Chitinase plays a pivotal role in the enzymatic preparation of COSs. Herein, a cold-adapted and efficient chitinase (ChiTg) from the marine Trichoderma gamsii R1 was purified and characterized. The optimal temperature of ChiTg was 40 °C, and the relative activity at 5 °C was above 40.1%. Meanwhile, ChiTg was active and stable from pH 4.0 to 7.0. As an endo-type chitinase, ChiTg exhibited the highest activity with colloidal chitin, then with ball-milled and powdery chitin. In addition, ChiTg showed high efficiency when hydrolyzing colloidal chitin at different temperatures, and the end products were mainly composed of COSs with one to three degrees of polymerization. Furthermore, the results of bioinformatics analysis revealed that ChiTg belongs to the GH18 family, and its acidic surface and the flexible structure of its catalytic site may contribute to its high activity in cold conditions. The results of this study provide a cold-active and efficient chitinase and ideas for its application regarding the preparation of COSs from colloidal chitin.

Effectors with chitinase activity (EWCAs), a family of conserved, secreted fungal chitinases that suppress chitin-triggered immunity

In plants, chitin-triggered immunity is one of the first lines of defense against fungi, but phytopathogenic fungi have developed different strategies to prevent the recognition of chitin. Obligate biotrophs such as powdery mildew fungi suppress the activation of host responses; however, little is known about how these fungi subvert the immunity elicited by chitin. During epiphytic growth, the cucurbit powdery mildew fungus Podosphaera xanthii expresses a family of candidate effector genes comprising nine members with an unknown function. In this work, we examine the role of these candidates in the infection of melon (Cucumis melo L.) plants, using gene expression analysis, RNAi silencing assays, protein modeling and protein-ligand predictions, enzymatic assays, and protein localization studies. Our results show that these proteins are chitinases that are released at pathogen penetration sites to break down immunogenic chitin oligomers, thus preventing the activation of chitin-triggered immunity. In addition, these effectors, designated effectors with chitinase activity (EWCAs), are widely distributed in pathogenic fungi. Our findings reveal a mechanism by which fungi suppress plant immunity and reinforce the idea that preventing the perception of chitin by the host is mandatory for survival and development of fungi in plant environments.

Endo-chitinase Chit33 specificity on different chitinolytic materials allows the production of unexplored chitooligosaccharides with antioxidant activity

The biological activity of chitooligosaccharides (COS) has made them targets for industrial and medical sectors. In this work, endo-chitinase Chit33 from Trichoderma harzianum CECT 2413 was expressed in Pichia pastoris GS115 to levels never achieved before (630 mg/L; 3.3 U/mL), without its biochemical characteristics being substantially affected. Chit33 produced a mixture of fully and partially acetylated COS from different chitin derivatives. HPAEC-PAD Chromatography and mass spectrometry analyses showed that (GlcNAc)₄ and GlcN-(GlcNAc)₂ were mainly produced from colloidal chitin and chitosan, respectively. COS in reaction mixtures were fragmented according to their size and their antioxidant activity analyzed by reducing power and free radical scavenging activity essays. The highest antioxidant activity was achieved with COS in the range of 0.5-2 and 2-10 kDa produced from colloidal chitin and chitosan, respectively, which gives biotechnological potential to both the chitin derivatives of 0.5-10 kDa and the biocatalyst producing them.

Enzymatic Modification of Native Chitin and Conversion to Specialty Chemical Products

: Chitin is one of the most abundant biomolecules on earth, occurring in crustacean shells and cell walls of fungi. While the polysaccharide is threatening to pollute coastal ecosystems in the form of accumulating shell-waste, it has the potential to be converted into highly profitable derivatives with applications in medicine, biotechnology, and wastewater treatment, among others. Traditionally this is still mostly done by the employment of aggressive chemicals, yielding low quality while producing toxic by-products. In the last decades, the enzymatic conversion of chitin has been on the rise, albeit still not on the same level of cost-effectiveness compared to the traditional methods due to its multi-step character. Another severe drawback of the biotechnological approach is the highly ordered structure of chitin, which renders it nigh impossible for most glycosidic hydrolases to act upon. So far, only the Auxiliary Activity 10 family (AA10), including lytic polysaccharide monooxygenases (LPMOs), is known to hydrolyse native recalcitrant chitin, which spares the expensive first step of chemical or mechanical pre-treatment to enlarge the substrate surface. The main advantages of enzymatic conversion of chitin over conventional chemical methods are the biocompability and, more strikingly, the higher product specificity, product quality, and yield of the process. Products with a higher Mw due to no unspecific depolymerisation besides an exactly defined degree and pattern of acetylation can be yielded. This provides a new toolset of thousands of new chitin and chitosan derivatives, as the physio-chemical properties can be modified according to the desired application. This review aims to provide an overview of the biotechnological tools currently at hand, as well as challenges and crucial steps to achieve the long-term goal of enzymatic conversion of native chitin into specialty chemical products.

A potent chitin-hydrolyzing enzyme from Myrothecium verrucaria affects growth and development of Helicoverpa armigera and plant fungal pathogens

Chitin, a crucial structural and functional component of insects and fungi, serves as a target for pest management by utilizing novel chitinases. Here, we report the biocontrol potential of recombinant Myrothecium verrucaria endochitinase (rMvEChi) against insect pest and fungal pathogens. A complete ORF of MvEChi (1185 bp) was cloned and heterologously expressed in Escherichia coli. Structure based sequence alignment of MvEChi revealed the presence of conserved domains SXGG and DXXDXDXE specific for GH-18 family, involved in substrate binding and catalysis, respectively. rMvEChi (46.6 kDa) showed optimum pH and temperature as 7.0 and 30 °C, respectively. Furthermore, rMvEChi remained stable within the pH range of 6.0 to 8.0 and up to 40 °C. rMvEChi exhibited k_cat/K_m values of 129.83 × 10³ [(g/L)^-1 s^-1] towards 4MU chitotrioside. Hydrolysis of chitooligosaccharides with various degrees of polymerization (DP) using rMvEChi indicated the release of DP2 as main end product with order of reaction as DP6 > DP5 > DP4 > DP3. Bioassay of rMvEChi against Helicoverpa armigera displayed potent anti-feedant activity and induced mortality. In vitro antifungal activity against plant pathogenic fungi (Ustilago maydis and Bipolaris sorokiniana) exhibited significant inhibition of mycelium growth. These results suggest that MvEChi has significant potential in enzyme-based pest and pathogen management.

Microbial contamination in methanol biofilters inoculated with a pure strain of Pichia pastoris: A potential limitation for waste revalorization

Novel biotechnologies to valorize waste emissions are based on the use of specialized microbial groups that produce different compounds of industrial interest. On this scenario, the retention of such specific microorganisms in the system is of critical interest; however, the potential limitations of working with simplified cultures in a competitive open environment are neither fully explored nor well understood. In this work, a series of biofilters treating methanol vapors coupled with heterologous endochitinase production were used to evaluate the performance of a specialized microbial population during a typical open-to-environment operation. The biofilters were inoculated with a transformed strain of Pichia pastoris and were operated identically for about 90 days. The results showed that the biofiltration performance became diverse with time in terms of the elimination capacity (EC) shifting from a variation coefficient of 1.5% (EC = 274 ± 24, 279 ± 5, and 281.9 ± 25 g/[m³ h]) at the beginning of the operation to 33% (EC = 297 ± 9, 338 ± 7, and 341 ± 2 g/[m³ h]) at the end of operation. Epifluorescence analysis and cloning-sequencing suggested that P. pastoris remained as the dominant microorganism of methanol degradation, whereas diverse airborne bacteria, including Ochrobactrum spp. and Klebsiella oxytoca, played a secondary role possibly associated with the consumption of intermediates. Overall, this study found that low diversity systems operated under non-sterile conditions could be susceptible to contamination with external microorganisms causing a diversifying behavior at the performance and microbial community levels. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2715, 2019.

Endochitinase 1 (Tv-ECH1) from Trichoderma virens has high subsite specificities for acetylated units when acting on chitosans

Chitosans with defined characteristics have been shown to possess reproducible bioactivities for numerous applications. A promising approach for producing chitosans with defined degrees of polymerization (DP), degrees of acetylation (DA), and patterns of acetylation (PA) involves using chitin-modifying enzymes. One such enzyme, the chitinase Tv-ECH1 belonging to the glycoside hydrolase (GH) family 18, seems to have an important role in the biocontrol properties of the fungus Trichoderma virens, suggesting its potential in generating novel chitosans for plant health applications. In this study, the Tv-ECH1 enzyme was overexpressed in the methylotrophic yeast Pichia pastoris, yielding large amounts (up to 2mgmL^-1) of purified recombinant enzyme of high activity, high purity, and high stability, making the system promising for industrial production of Tv-ECH1. The purified Tv-ECH1 chitinase displayed a wide optimal pH range from 4.5 to 6 and an optimal temperature of 37°C. Detailed subsite specificity analyses revealed high preference for acetylated residues at all four subsites analyzed (-2, -1, +1, +2), making Tv-ECH1 a promising candidate for the biotechnological production of specific chitosan oligomers and for the characterization of chitosan polymers via enzymatic fingerprinting.

Use of chitin and chitosan to produce new chitooligosaccharides by chitinase Chit42: enzymatic activity and structural basis of protein specificity

Background

Chitinases are ubiquitous enzymes that have gained a recent biotechnological attention due to their ability to transform biological waste from chitin into valued chito-oligomers with wide agricultural, industrial or medical applications. The biological activity of these molecules is related to their size and acetylation degree. Chitinase Chit42 from Trichoderma harzianum hydrolyses chitin oligomers with a minimal of three N-acetyl-d-glucosamine (GlcNAc) units. Gene chit42 was previously characterized, and according to its sequence, the encoded protein included in the structural Glycoside Hydrolase family GH18.

Results

Chit42 was expressed in Pichia pastoris using fed-batch fermentation to about 3 g/L. Protein heterologously expressed showed similar biochemical properties to those expressed by the natural producer (42 kDa, optima pH 5.5–6.5 and 30–40 °C). In addition to hydrolyse colloidal chitin, this enzyme released reducing sugars from commercial chitosan of different sizes and acetylation degrees. Chit42 hydrolysed colloidal chitin at least 10-times more efficiently (defined by the k_cat/K_m ratio) than any of the assayed chitosan. Production of partially acetylated chitooligosaccharides was confirmed in reaction mixtures using HPAEC-PAD chromatography and mass spectrometry. Masses corresponding to (d-glucosamine)_1–8-GlcNAc were identified from the hydrolysis of different substrates. Crystals from Chit42 were grown and the 3D structure determined at 1.8 Å resolution, showing the expected folding described for other GH18 chitinases, and a characteristic groove shaped substrate-binding site, able to accommodate at least six sugar units. Detailed structural analysis allows depicting the features of the Chit42 specificity, and explains the chemical nature of the partially acetylated molecules obtained from analysed substrates.

Conclusions

Chitinase Chit42 was expressed in a heterologous system to levels never before achieved. The enzyme produced small partially acetylated chitooligosaccharides, which have enormous biotechnological potential in medicine and food. Chit42 3D structure was characterized and analysed. Production and understanding of how the enzymes generating bioactive chito-oligomers work is essential for their biotechnological application, and paves the way for future work to take advantage of chitinolytic activities.

Electronic supplementary material

The online version of this article (10.1186/s12934-018-0895-x) contains supplementary material, which is available to authorized users.

Constitutive expression of the active fragment of human vasostatin Vs30 in Pichia pastoris SMD1168H

Vasostatin 30 (Vs30) is an active fragment derived from the N-terminal region (135-164 aa) of human calreticulin and has the ability to inhibit angiogenesis. In this work, the expression of Vs30 was performed using a protease-deficient strain of the methylotrophic yeast Pichia pastoris. The vs30 gene was optimized for P. pastoris preferential codon usage and inserted into constitutive expression vector pGAPZαA. In addition, a plasmid with four copies of the expression cassette was obtained and transformed into P. pastoris. The flask fermentation conditions were: culture volume of 25 mL in 250 mL baffled flasks at 28 °C, pH 6 and harvest time of 48 h. Up to 21.07 mg/L Vs30 were attained and purified by ultrafiltration with a 30-kDa cut-off membrane and the recovery was 49.7%. Bioactivity of Vs30 was confirmed by the inhibition of cell proliferation, as well as the inhibition of the capillary-like structures formation of EA.hy926 cells in vitro. This work constitutes the first report on the expression of Vs30 in Pichia pastoris using a constitutive promoter and multi-copy approach such as strategies to improve the recombinant Vs30 expression.

Expression of grape class IV chitinase in Spodoptera frugiperda (Sf9) insect cells

INTRODUCTION

Most of pathogenesis related (PR) proteins possess complicated structures; hence their active recombinant forms are usually produced in eukaryotic systems. In this study, we employed an insect cell line to express a recombinant form of a previously identified grape PR3 allergen categorised as class IV chitinase.

METHODS

Grape chitinase cDNA was amplified by RT-PCR and inserted into pFastBacHTA using restriction enzymes. The recombinant pFastBacHTA was applied for the transformation of Escherichia coli DH10Bac cells. The purified recombinant bacmid was used for transfection of Sf9 cells. Finally, the IgE-immunoreactivity of purified recombinant protein was evaluated using grape allergic patient's sera. Moreover, polyclonal anti-6His-tag and monoclonal anti-chitinase antibodies were used for further assessment of recombinant protein.

RESULTS

SDS-PAGE analysis of the transfected Sf9 cells showed expression of a monomeric 25kDa and a dimeric 50 kDa recombinant protein. Western blotting revealed considerable IgE reactivity of the recombinant protein with grape allergic patients' sera. Furthermore, confirmatory assays showed specific reactivity of the recombinant protein with anti-His tag and anti-chitinase antibodies.

CONCLUSION

This study showed that, in contrast to E. coli, insect cells are suitable hosts for the production of a soluble and IgE-reactive recombinant form of grape class IV chitinase. This recombinant allergen could be used for component resolved diagnosis of grape allergy or other immunodiagnostic purposes.

Codon optimisation improves the expression of Trichoderma viride sp. endochitinase in Pichia pastoris

The mature cDNA of endochitinase from Trichoderma viride sp. was optimised based on the codon bias of Pichia pastoris GS115 and synthesised by successive PCR; the sequence was then transformed into P. pastoris GS115 via electroporation. The transformant with the fastest growth rate on YPD plates containing 4 mg/mL G418 was screened and identified. This transformant produced 23.09 U/mL of the recombinant endochitinase, a 35% increase compared to the original strain bearing the wild-type endochitinase cDNA. The recombinant endochitinase was sequentially purified by ammonia sulphate precipitation, DE-52 anion-exchange chromatography and Sephadex G-100 size-exclusion chromatography. Thin-layer chromatography indicated that the purified endochitinase could hydrolyse chito-oligomers or colloidal chitin to generate diacetyl-chitobiose (GlcNAc)₂ as the main product. This study demonstrates (1) a means for high expression of Trichoderma viride sp. endochitinase in P. pastoris using codon optimisation and (2) the preparation of chito-oligomers using endochitinase.

High-yield production of a chitinase from Aeromonas veronii B565 as a potential feed supplement for warm-water aquaculture

Chitin, present in crustacean shells, insects, and fungi, is the second most plentiful natural organic fiber after wood. To effectively use chitin in a cost-saving and environmentally friendly way in aquaculture, crustacean shells (e.g., shrimp-shell meal) are supplemented into aquafeed after degradation by chemical methods. Herein, we describe a chitinase from Aeromonas veronii B565, designated ChiB565, which potently degrades shrimp-shell chitin and resists proteolysis. We isolated recombinant ChiB565 of the expected molecular mass in large yield from Pichia pastoris. ChiB565 is optimally active at pH 5.0 and 50 °C and stable between pH 4.5 and 9.0 at 50 °C and below. Compared with the commercial chitinase C-6137, which cannot degrade shrimp-shell chitin, ChiB565 hydrolyzes shrimp-shell chitin in addition to colloidal chitin, powdered chitin, and β-1,3-1,4-glucan. The optimal enzyme concentration and reaction time for in vitro degradation of 0.1 g of powdered shrimp shell are 30 U of ChiB565 and 3 h, respectively. A synergistic protein-release effect occurred when ChiB565 and trypsin were incubated in vitro with shrimp shells. Tilapia were fed an experimental diet containing 5% (w/w) shrimp bran and 16.2 U/kg ChiB565, which significantly improved growth and feed conversion compared with a control diet lacking ChiB565. Dietary ChiB565 enhanced nitrogen digestibility and downregulated intestinal IL-1β expression. The immunologically relevant protective effects of dietary ChiB565 were also observed for 2 to 3 days following exposure to pathogenic Aeromonas hydrophila.

Fungal chitinases: diversity, mechanistic properties and biotechnological potential

Chitin derivatives, chitosan and substituted chito-oligosaccharides have a wide spectrum of applications ranging from medicine to cosmetics and dietary supplements. With advancing knowledge about the substrate-binding properties of chitinases, enzyme-based production of these biotechnologically relevant sugars from biological resources is becoming increasingly interesting. Fungi have high numbers of glycoside hydrolase family 18 chitinases with different substrate-binding site architectures. As presented in this review, the large diversity of fungal chitinases is an interesting starting point for protein engineering. In this review, recent data about the architecture of the substrate-binding clefts of fungal chitinases, in connection with their hydrolytic and transglycolytic abilities, and the development of chitinase inhibitors are summarized. Furthermore, the biological functions of chitinases, chitin and chitosan utilization by fungi, and the effects of these aspects on biotechnological applications, including protein overexpression and autolysis during industrial processes, are discussed in this review.

Expression of recombinant endochitinase from the Antarctic bacterium, Sanguibacter antarcticus KOPRI 21702 in Pichia pastoris by codon optimization

An endochitinase was previously purified and the gene was cloned from the psychrophilic Antarctic bacterium, Sanguibacter antarcticus (KCTC 13143). In the present study, recombinant endochitinase, rChi21702, was expressed using a yeast expression system (Pichia pastoris) and codon optimization. The expressed rChi21702 was purified by Phenyl-Sepharose column chromatography. Optimal expression yielded 1-mg purified enzyme from 1-L bioreactor culture. When p-NP-(GlcNAc)(2) was used as a substrate, the specific activity of the enzyme was determined to be 20U/mg. In vitro assays and thin-layer chromatography demonstrated that the recombinant enzyme has endochitinase activity that produces diacetyl-chitobiose as a dominant end product when chitooligomers, colloidal chitin, and the chromogenic p-NP-(GlcNAc)(2) are used as substrates. Optimal activity for rChi21702 was observed at 37 degrees C and a pH of 7.6. Interestingly, rChi21702 exhibited 63% of optimal activity at 10 degrees C and 44% activity at 0 degrees C. Taken together, the results indicate that rChi21702 has psychrotolerant endochitinase activity even after recombinant expression in yeast cells.

Expression, purification, and analyses of glycosylation and disulfide bonds of Stereum purpureum endopolygalacturonase I in Pichia pastoris

We have succeeded in the expression of Stereum purpureum endopolygalacturonase I (EndoPG I) using the Pichia expression system and in purification of the three kinds of recombinant EndoPG I, which have one to three sugar chains by using CM52 column chromatography. The sugar chains which were added to EndoPG I were the M8, M9, and/or M10 high-mannose type. The results of LC-MS analysis showed that recombinant EndoPG Is were randomly glycosylated at four N-glycosylation sites. From the thermal denaturation curves of the recombinant enzymes, it was suggested that EndoPG I differing in thermal stability was included in the sample after purification. Therefore, we investigated the disulfide bonds of recombinant EndoPG I by LC-MS analysis. As a result, peptides without a second or third disulfide bond were detected. This result is the first indicating that there are incomplete enzymes in terms of disulfide bonds in the Pichia expression system.