Production and purification of extracellular chitinases from Penicillium aculeatum NRRL 2129 under solid-state fermentation

Cactus Endophytic Fungi and Bioprospecting for their Enzymes and Bioactive Molecules: A Systematic Review

Endophytic fungi are associated with plant health and represent a remarkable source of potential of enzymes and bioactive compounds, but the diversity of endophytes remains uncertain and poorly explored, especially in Cactaceae, one of the most species-rich families adapted to growing in arid and semi-arid regions. The aim of this study was to conduct a systematic review on the diversity and bioprospecting of endophytic fungi from Cactaceae. We analysed peer-reviewed articles from seven databases using PRISMA guidelines. The results showed that the Cactaceae family is a source of new taxa, but the diversity of endophytic fungi of Cactaceae is little explored, mainly the diversity among tissues and by metagenomics. Bioprospecting studies have shown that these microorganisms can be used in the production of enzymes and larvicidal and antifungal compounds. Our results are relevant as a starting point for researchers to develop studies that expand the knowledge of plant mycobiota in arid and semi-arid ecosystems, as well as comprising a remarkable source of fungal compounds with several biotechnological applications.

Isolation, biochemical characterization, and genome sequencing of two high-quality genomes of a novel chitinolytic Jeongeupia species

Chitin is the second most abundant polysaccharide worldwide as part of arthropods' exoskeletons and fungal cell walls. Low concentrations in soils and sediments indicate rapid decomposition through chitinolytic organisms in terrestrial and aquatic ecosystems. The enacting enzymes, so-called chitinases, and their products, chitooligosaccharides, exhibit promising characteristics with applications ranging from crop protection to cosmetics, medical, textile, and wastewater industries. Exploring novel chitinolytic organisms is crucial to expand the enzymatical toolkit for biotechnological chitin utilization and to deepen our understanding of diverse catalytic mechanisms. In this study, we present two long-read sequencing-based genomes of highly similar Jeongeupia species, which have been screened, isolated, and biochemically characterized from chitin-amended soil samples. Through metabolic characterization, whole-genome alignments, and phylogenetic analysis, we could demonstrate how the investigated strains differ from the taxonomically closest strain Jeongeupia naejangsanensis BIO-TAS4-2T (DSM 24253). In silico analysis and sequence alignment revealed a multitude of highly conserved chitinolytic enzymes in the investigated Jeongeupia genomes. Based on these results, we suggest that the two strains represent a novel species within the genus of Jeongeupia, which may be useful for environmentally friendly N-acetylglucosamine production from crustacean shell or fungal biomass waste or as a crop protection agent.

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 and characterization of chitinase produced by thermophilic fungi Thermomyces lanuginosus

BACKGROUND

In the past few years, the production of shrimp shell waste from the seafood processing industries has confronted a significant surge. Furthermore, insignificant dumping of waste has dangerous effects on both nature and human well-being. This marine waste contains a huge quantity of chitin which has several applications in different fields. The chitinase enzyme can achieve degradation of chitin, and the chitin itself can be used as the substrate as well for production of chitinase. In the current study, the chitinase enzyme was produced by Thermomyces lanuginosus. The extracellular chitinase was purified from crude extract using ammonium sulfate precipitation followed by DEAE-cellulose ion-exchange chromatography and Sephadex G-100 gel filtration chromatography. The stability and activity of chitinase with different pH, temperature, different times for a reaction, in the presence of different metal ions, and different concentration of enzyme and substrate were analyzed.

RESULT

The chitinase activity was found to be highest at pH 6.5, 50 °C, and 60 min after the reaction began. and the chitinase showed the highest activity and stability in the presence of β-mercaptoethanol (ME). The SDS-PAGE of denatured purified chitinase showed a protein band of 18 kDa.

CONCLUSION

The characterization study concludes that Cu²⁺, Hg²⁺, and EDTA have an inhibitory effect on chitinase activity, whereas β-ME acts as an activator for chitinase activity. The utilization of chitin to produce chitinase and the degradation of chitin using that chitinase enzyme would be an opportunity for bioremediation of shrimp shell waste.

Polyextremophilic Chitinolytic Activity by a Marine Strain (IG119) of Clonostachys rosea

The investigation for novel unique extremozymes is a valuable business for which the marine environment has been overlooked. The marine fungus Clonostachys rosea IG119 was tested for growth and chitinolytic enzyme production at different combinations of salinity and pH using response surface methodology. RSM modelling predicted best growth in-between pH 3.0 and 9.0 and at salinity of 0-40‱, and maximum enzyme activity (411.137 IU/L) at pH 6.4 and salinity 0‱; however, quite high production (>390 IU/L) was still predicted at pH 4.5-8.5. The highest growth and activity were obtained, respectively, at pH 4.0 and 8.0, in absence of salt. The crude enzyme was tested at different salinities (0-120‱) and pHs (2.0-13.0). The best activity was achieved at pH 4.0, but it was still high (in-between 3.0 and 12.0) at pH 2.0 and 13.0. Salinity did not affect the activity in all tested conditions. Overall, C. rosea IG119 was able to grow and produce chitinolytic enzymes under polyextremophilic conditions, and its crude enzyme solution showed more evident polyextremophilic features. The promising chitinolytic activity of IG119 and the peculiar characteristics of its chitinolytic enzymes could be suitable for several biotechnological applications (i.e., degradation of salty chitin-rich materials and biocontrol of spoiling organisms, possibly solving some relevant environmental issues).

Colonization of Beauveria bassiana 08F04 in root-zone soil and its biocontrol of cereal cyst nematode (Heterodera filipjevi)

Cereal cyst nematodes cause serious yield losses of wheat in Hunaghuai winter wheat growing region in China. Beauveria bassiana 08F04 isolated from the surface of cysts is a promising biological control agent for cereal cyst nematodes. As the colonization capacity is a crucial criteria to assess biocontrol effectiveness for a microbial agent candidate, we aimed to label B. bassiana 08F04 for efficient monitoring of colonization in the soil. The binary pCAM-gfp plasmid containing sgfp and hph was integrated into B. bassiana 08F04 using the Agrobacterium tumefaciens-mediated transformation. The transformation caused a significant change in mycelial and conidial yields, and in extracellular chitinase activity in some transformants. The cultural filtrates of some transformants also decreased acetylcholinesterase activity and the survival of Heterodera filipjevi second-stage juveniles relative to the wild-type strain. One transformant (G10) had a growth rate and biocontrol efficacy similar to the wild-type strain, so it was used for a pilot study of B. bassiana colonization conducted over 13 weeks. Real-time PCR results and CFU counts revealed that the population of G10 increased quickly over the first 3 weeks, then decreased slowly over the following 4 weeks before stabilizing. In addition, the application of wild-type B. bassiana 08F04 and transformant G10 significantly reduced the number of H. filipjevi females in roots by 64.4% and 60.2%, respectively. The results of this study have practical applications for ecological, biological and functional studies of B. bassiana 08F04 and for bionematicide registration.

Talaromyces halophytorum sp. nov. Isolated from Roots of Limonium tetragonum in Korea

Talaromyces halophytorum sp. nov. was isolated from the roots of halophyte Limonium tetragonum collected from Seocheon-gun, Korea in November 2015. It showed a slow growth on yeast extract sucrose agar at 25 °C, no growth at 4 °C or 37 °C and produced smooth-walled and globose to sub-globose conidia. T. halophytorum is phylogenetically distinct from the other reported Talaromyces species of section Trachyspermi based on multi-locus sequence typing results using partial fragments of β-tubulin, calmodulin, ITS, and RNA polymerase II genes.

Production and characterization of a thermostable antifungal chitinase secreted by the filamentous fungus Aspergillus niveus under submerged fermentation

The filamentous fungus Aspergillus niveus produced extracellular antifungal chitinase when cultured under submerged fermentation (SbmF) using crab shells as the carbon source. Maximal chitinase production was achieved at 192 h of cultivation using minimal medium containing 1% chitin. The enzyme was purified 1.97-fold with 40% recovery by ammonium sulfate precipitation and Sephadex G-100 gel filtration. The molecular mass was estimated to be 44 kDa by both 12% SDS-PAGE and Sepharose CL-6B gel filtration. Maximal A. niveus chitinase activity was obtained at 65 °C and pH 5.0. The enzyme was fully stable at 60 °C for up to 120 min and the enzymatic activity was increased by Mn²⁺. In the presence of reducing and denaturing compounds, the enzyme activity was not drastically affected. The chitinase was able to hydrolyze colloidal chitin, azure chitin, and 4-nitrophenyl N-acetyl-β-D glucosaminide; for the latter, the K_0.5 and maximal velocity (V_max) were 3.51 mM and 9.68 U/mg of protein, respectively. The A. niveus chitinase presented antifungal activity against Aspergillus niger (MIC = 84 µg/mL), A. fumigatus (MIC = 21 µg/mL), A. flavus (MIC = 24 µg/mL), A. phoenicis (MIC = 24 µg/mL), and Paecilomyces variotii (MIC = 21 µg/mL). The fungus A. niveus was able to produce a thermostable and denaturation-resistant chitinase able to inhibit fungal development, signaling its biotechnological potential.

Multilocus phylogenetic analysis of Talaromyces species isolated from cucurbit plants in China and description of two new species, T. cucurbitiradicus and T. endophyticus

During a survey of endophytic fungi from cucurbit plants in China, 21 Talaromyces strains were isolated from ten symptomless plants. Phylogenetic analysis of the partial RNA polymerase II largest subunit gene (RPB2) showed that the strains belong to Talaromyces sections Talaromyces and Islandici. Based on morphological characters and multilocus phylogenetic analysis of the nuc rDNA internal transcribed spacer region (ITS1-5.8S-ITS2 = ITS), calmodulin (CaM), and β-tubulin (TUB) genes, the strains were identified as four known species, T. cnidii, T. pinophilus, T. radicus, and T. wortmannii, and two new species. Two new species, T. cucurbitiradicus from pumpkin roots and T. endophyticus from cucumber stems, are described in this study. Talaromyces cucurbitiradicus is morphologically similar to T. funiculosus but differs in the number of phialides per metula and by the production of chlamydospores. Talaromyces endophyticus is morphologically similar to T. cerinus and T. chlamydosporus but differs by producing yellowish colonies and by lacking chlamydospores. Further analyses of polymorphisms in ITS and TUB sequences supported the distinctions among T. cucurbitiradicus, T. endophyticus, and similar species.

Production of antifungal chitinase by Aspergillus niger LOCK 62 and its potential role in the biological control

Aspergillus niger LOCK 62 produces an antifungal chitinase. Different sources of chitin in the medium were used to test the production of the chitinase. Chitinase production was most effective when colloidal chitin and shrimp shell were used as substrates. The optimum incubation period for chitinase production by Aspergillus niger LOCK 62 was 6 days. The chitinase was purified from the culture medium by fractionation with ammonium sulfate and affinity chromatography. The molecular mass of the purified enzyme was 43 kDa. The highest activity was obtained at 40 °C for both crude and purified enzymes. The crude chitinase activity was stable during 180 min incubation at 40 °C, but purified chitinase lost about 25 % of its activity under these conditions. Optimal pH for chitinase activity was pH 6-6.5. The activity of crude and purified enzyme was stabilized by Mg(2+) and Ca(2+) ions, but inhibited by Hg(2+) and Pb(2+) ions. Chitinase isolated from Aspergillus niger LOCK 62 inhibited the growth of the fungal phytopathogens: Fusarium culmorum, Fusarium solani and Rhizoctonia solani. The growth of Botrytis cinerea, Alternaria alternata, and Fusarium oxysporum was not affected.

Biodegradation of shrimp processing bio-waste and concomitant production of chitinase enzyme and N-acetyl-D-glucosamine by marine bacteria: production and process optimization

A total of 250 chitinolytic bacteria from 68 different marine samples were screened employing enrichment method that utilized native chitin as the sole carbon source. After thorough screening, five bacteria were selected as potential cultures and identified as; Stenotrophomonas sp. (CFR221 M), Vibrio sp. (CFR173 M), Phyllobacteriaceae sp. (CFR16 M), Bacillus badius (CFR198 M) and Bacillus sp. (CFR188 M). All five strains produced extracellular chitinase and GlcNAc in SSF using shrimp bio-waste. Scanning electron microscopy confirmed the ability of these marine bacteria to adsorb onto solid shrimp bio-waste and to degrade chitin microfibers. HPLC analysis of the SSF extract also confirmed presence of 36-65 % GlcNAc as a product of the degradation. The concomitant production of chitinase and GlcNAc by all five strains under SSF using shrimp bio-waste as the solid substrate was optimized by 'one factor at a time' approach. Among the strains, Vibrio sp. CFR173 M produced significantly higher yields of chitinase (4.8 U/g initial dry substrate) and GlcNAc (4.7 μmol/g initial dry substrate) as compared to other cultures tested. A statistically designed experiment was applied to evaluate the interaction of variables in the biodegradation of shrimp bio-waste and concomitant production of chitinase and GlcNAc by Vibrio sp. CFR173 M. Statistical optimization resulted in a twofold increase of chitinase, and a 9.1 fold increase of GlcNAc production. These results indicated the potential of chitinolytic marine bacteria for the reclamation of shrimp bio-waste, as well as the potential for economic production of chitinase and GlcNAc employing SSF using shrimp bio-waste as an ideal substrate.

Expression of chitinase genes of Metarhizium anisopliae isolates in lepidopteran pests and on synthetic media

Pathogenecity of the well characterized entomopathogenic fungus Metarhizium anisopliae used for biocontrol of a wide range of insect pests secretes hydrolytic enzymes that degrade the host cuticle. The chitinolytic activity of high and low virulent isolates of M. anisopliae was assayed on minimal medium (MM) + colloidal chitin and MM supplemented with insect cuticles. Ex- pression pattern of four chitinase genes (chitinase (chi), chi 1, chi 2, chi 3) was profiled during pathogenic stages of the entomopathogen under in vitro and in vivo conditions. Reverse-transcription polymerase chain reaction (RT-PCR) analysis confirmed that chitinase cDNAs were expressed during the germination of fungus under nutrient-deprived conditions. RT-PCR analysis performed for the four chitinase genes on the two insect hosts Spodoptera litura and Helicoverpa armigera at six developmental stages of the pathogen displayed up-regulation in S. litura at mycosed and conidiated condition while with H. armigera there was expression only after 48 h of incubation. Differential expression of chi, chi 1 and chi 2 genes in vitro (nitrogen rich and nitrogen limiting media) and in vivo (live insect hosts S. litura and H. armigera) implicate the role of substrate differences in pathogenesis.

Solid state fermentation production of chitin deacetylase by Colletotrichum lindemuthianum ATCC 56676 using different substrates

Production of extracellular chitin deacetylase by Colletotrichum lindemuthianum ATCC 56676 under solid substrate fermentation was studied. The suitability of shrimp shell chitin waste (SSCW) and commercial wheat bran (CWB) was evaluated for maximal enzyme production. CWB medium (pH 6.4 ± 0.2) supplemented with chitosan favoured maximal chitin deacetylase yield of 460.4 ± 14.7 unit/g initial dry substrate (U/g IDS) at 96 h as compared to maximal yield of 392.0 ± 6.4 U/g IDS at 192 h in SSCW medium (pH 8.7 ± 0.2) at 25 °C incubation temperature and 60% (w/w) initial moisture content of medium. Along with chitin deacetylase, C. lindemuthianum ATCC 56676 produced maximum endo-chitinase (0.28 ± 0.03 U/g IDS at 144 h) and β-N-acetylhexosaminidase (0.79 ± 0.009 U/g IDS at 192 h) in CWB medium and 0.49 ± 0.05 U/g IDS of endo-chitinase at 264 h and 0.38 ± 0.04 U/g IDS of β-N-acetylhexosaminidase at 96 h of incubation in SSCW medium. SEM studies indicated the difference in the morphology of mycelia and hyphae of C. lindemuthianum ATCC 56676 when grown on different solid substrates. Production of chitin deacetylase by SSF is being reported for the first time.

The extracellular β-1,3-endoglucanase EngA is involved in autolysis of Aspergillus nidulans

AIMS

To elucidate the roles of the β-1,3-endoglucanase EngA in autolysis of the filamentous fungus Aspergillus nidulans and to identify the common regulatory elements of autolytic hydrolases.

METHODS AND RESULTS

A β-1,3-endoglucanase was purified from carbon-starving cultures of A. nidulans. This enzyme is found to be encoded by the engA gene (locus ID: AN0472.3). Functional and gene-expression studies demonstrated that EngA is involved in the autolytic cell wall degradation resulting from carbon starvation of the fungus. Moreover, regulation of engA is found to be dependent on the FluG/BrlA asexual sporulation signalling pathway in submerged culture. The deletion of either engA or chiB (encoding an endochitinase) caused highly reduced production of hydrolases in general.

CONCLUSIONS

The β-1,3-endoglucanase EngA plays a pivotal role in fungal autolysis, and activities of both EngA and ChiB are necessary to orchestrate the expression of autolytic hydrolases. The production of cell wall-degrading enzymes was coordinately controlled in a highly sophisticated and complex manner.

SIGNIFICANCE AND IMPACT OF THE STUDY

No information was available on the autolytic glucanase(s) of the euascomycete A. nidulans. This study demonstrates that EngA is a key element in fungal autolysis, and normal activities of both EngA and ChiB are crucial for balanced production of hydrolases.

Exploitation of biological wastes for the production of value-added products under solid-state fermentation conditions

Biological wastes contain several reusable substances of high value such as soluble sugars and fibre. Direct disposal of such wastes to soil or landfill causes serious environmental problems. Thus, the development of potential value-added processes for these wastes is highly attractive. These biological wastes can be used as support-substrates in solid-state fermentation (SSF) to produce industrially relevant metabolites with great economical advantage. In addition, it is an environmentally friendly method of waste management. This paper reviews the reutilization of biological wastes for the production of value-added products using the SSF technique.

Comparative studies of differential expression of chitinolytic enzymes encoded by chiA, chiB, chiC and nagA genes in Aspergillus nidulans

N-Acetyl-D-glucosamine, chito-oligomers and carbon starvation regulated chiA, chiB, and nagA gene expressions in Aspergillus nidulans cultures. The gene expression patterns of the main extracellular endochitinase ChiB and the N-acetyl-beta-D-glucosaminidase NagA were similar, and the ChiB-NagA enzyme system may play a morphological and/or nutritional role during autolysis. Alterations in the levels of reactive oxygen species or in the glutathione-glutathione disulfide redox balance, characteristic physiological changes developing in ageing and autolyzing fungal cultures, did not affect the regulation of either the growth-related chiA or the autolysis-coupled chiB genes although both of them were down-regulated under diamide stress. The transcription of the chiC gene with unknown physiological function was repressed by increased intracellular superoxide concentration.