Cloning, expression, and characterization of a highly thermostable family 18 chitinase from Rhodothermus marinus

A novel bi-functional cold-adaptive chitinase from Chitinilyticum aquatile CSC-1 for efficient synthesis of N-acetyl-D-glucosaminidase

In order to better utilize chitinolytic enzymes to produce high-value N-acetyl-D-glucosamine (GlcNAc) from chitinous waste, there is an urgent need to explore bi-functional chitinases with exceptional properties of temperature, pH and metal tolerance. In this study, we cloned and characterized a novel bi-functional cold-adaptive chitinase called CaChi18A from a newly isolated strain, Chitinilyticum aquatile CSC-1, in Bama longevity village of Guangxi Province, China. The activity of CaChi18A at 50 °C was 4.07 U/mg. However, it exhibited significant catalytic activity even at 5 °C. Its truncated variant CaChi18A_ΔChBDs, containing only catalytic domain, demonstrated significant activity levels, exceeding 40 %, over a temperature range of 5-60 °C and a pH range of 3 to 10. It was noteworthy that it displayed tolerance towards most metal ions at a final concentration of 0.1 mM, including Fe3+ and Cu2+ ions, retaining 122.52 ± 0.17 % and 116.42 ± 1.52 % activity, respectively. Additionally, it exhibited favorable tolerance towards organic solvents with the exception of formic acid. Interestedly, CaChi18A and CaChi18A_ΔChBDs had a low Km value towards colloidal chitin (CC), 0.94 mg mL-1 and 2.13 mg mL-1, respectively. Both enzymes exhibited chitobiosidase and N-acetyl-D-glucosaminidase activities, producing GlcNAc as the primary product when hydrolyzing CC. The high activities across a broader temperature and pH range, strong environmental adaptability, and hydrolytic properties of CaChi18A_ΔChBDs suggested that it could be a promising candidate for GlcNAc production.

Mining thermophiles for biotechnologically relevant enzymes: evaluating the potential of European and Caucasian hot springs

The development of sustainable and environmentally friendly industrial processes is becoming very crucial and demanding for the rapid implementation of innovative bio-based technologies. Natural extreme environments harbor the potential for discovering and utilizing highly specific and efficient biocatalysts that are adapted to harsh conditions. This review focuses on extremophilic microorganisms and their enzymes (extremozymes) from various hot springs, shallow marine vents, and other geothermal habitats in Europe and the Caucasus region. These hot environments have been partially investigated and analyzed for microbial diversity and enzymology. Hotspots like Iceland, Italy, and the Azores harbor unique microorganisms, including bacteria and archaea. The latest results demonstrate a great potential for the discovery of new microbial species and unique enzymes that can be explored for the development of Circular Bioeconomy.Different screening approaches have been used to discover enzymes that are active at extremes of temperature (up 120 °C), pH (0.1 to 11), high salt concentration (up to 30%) as well as activity in the presence of solvents (up to 99%). The majority of published enzymes were revealed from bacterial or archaeal isolates by traditional activity-based screening techniques. However, the latest developments in molecular biology, bioinformatics, and genomics have revolutionized life science technologies. Post-genomic era has contributed to the discovery of millions of sequences coding for a huge number of biocatalysts. Both strategies, activity- and sequence-based screening approaches, are complementary and contribute to the discovery of unique enzymes that have not been extensively utilized so far.

A Contemporary Appraisal on Impending Industrial and Agricultural Applications of Thermophilic-Recombinant Chitinolytic Enzymes from Microbial Sources

The ability of chitinases to degrade the second most abundant polymer, chitin, into potentially useful chitooligomers and chitin derivatives has not only rendered them fit for chitinous waste management but has also made them important from industrial point of view. At the same time, they have also been recognized to have an imperative role as promising biocontrol agents for controlling plant diseases. As thermostability is an important property for an industrially important enzyme, various bacterial and fungal sources are being exploited to obtain such stable enzymes. These stable enzymes can also play a role in agriculture by maintaining their stability under adverse environmental conditions for longer time duration when used as biocontrol agent. Biotechnology has also played its role in the development of recombinant chitinases with enhanced activity, thermostability, fungicidal and insecticidal activity via recombinant DNA techniques. Furthermore, a relatively new approach of generating pathogen-resistant transgenic plants has opened new ways for sustainable agriculture by minimizing the yield loss of valuable crops and plants. This review focuses on the potential applications of thermostable and recombinant microbial chitinases in industry and agriculture.

Biotechnological Eminence of Chitinases: A Focus on Thermophilic Enzyme Sources, Production Strategies and Prominent Applications

BACKGROUND

Chitin, the second most abundant polysaccharide in nature, is a constantly valuable and renewable raw material after cellulose. Due to advancement in technology, industrial interest has grown to take advantage of the chitin.

OBJECTIVE

Now, biomass is being treated with diverse microbial enzymes or cells for the production of desired products under best industrial conditions. Glycosidic bonds in chitin structure are degraded by chitinase enzymes, which are characterized into number of glycoside hydrolase (GHs) families.

METHODS

Thermophilic microorganisms are remarkable sources of industrially important thermostable enzymes, having ability to survive harsh industrial processing conditions. Thermostable chitinases have an edge over mesophilic chitinases as they can hydrolyse the substrate at relatively high temperatures and exhibit decreased viscosity, significantly reduced contamination risk, thermal and chemical stability and increased solubility. Various methods are employed to purify the enzyme and increase its yield by optimizing various parameters such as temperature, pH, agitation, and by investigating the effect of different chemicals and metal ions etc. Results: Thermostable chitinase enzymes show high specific activity at elevated temperature which distinguish them from mesophiles. Genetic engineering can be used for further improvement of natural chitinases, and unlimited potential for the production of thermophilic chitinases has been highlighted due to advancement in synthetic biological techniques. Thermostable chitinases are then used in different fields such as bioremediation, medicine, agriculture and pharmaceuticals.

CONCLUSION

This review will provide information about chitinases, biotechnological potential of thermostable enzyme and the methods by which they are being produced and optimized for several industrial applications. Some of the applications of thermostable chitinases have also been briefly described.

Thermophilic Chitinases: Structural, Functional and Engineering Attributes for Industrial Applications

Chitin is the second most widely found natural polymer next to cellulose. Chitinases degrade the insoluble chitin to bioactive chitooligomers and monomers for various industrial applications. Based on their function, these enzymes act as biocontrol agents against pathogenic fungi and invasive pests compared with conventional chemical fungicides and insecticides. They have other functional roles in shellfish waste management, fungal protoplast generation, and Single-Cell Protein production. Among the chitinases, thermophilic and thermostable chitinases are gaining popularity in recent years, as they can withstand high temperatures and maintain the enzyme stability for longer periods. Not all chitinases are thermostable; hence, tailor-made thermophilic chitinases are designed to enhance their thermostability by direct evolution, genetic engineering involving mutagenesis, and proteomics approach. Although research has been done extensively on cloning and expression of thermophilic chitinase genes, there are only few papers discussing on the mechanism of chitin degradation using thermophiles. The current review discusses the sources of thermophilic chitinases, improvement of protein stability by gene manipulation, metagenomics approaches, chitin degradation mechanism in thermophiles, and their prospective applications for industrial, agricultural, and pharmaceutical purposes.

Purification and characterization of chitinase from Paenibacillus sp.

The chitinase-producing bacteria Paenibacillus sp. was isolated from soil samples. The chitinase was purified successively by ammonia sulfate fractional precipitation followed by chromatography on DEAE 52-cellulose column and then on Sephadex G-75 column. The chitinase has a molecular weight of ca. 30 kDa as measured by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis. Its optimum pH is 4.5, and its optimum temperature is 50 °C with colloidal chitin as a substrate. The enzyme is stable below 45 °C and in pH ranges between 4.5 and 5.5. It is activated by glucosamine, glucose, N-acetylglucosamine, and metal ions including Ca²⁺ , Fe²⁺ , Fe³⁺ , and Ni²⁺ . It is inhibited by SDS, H₂ O₂ , ascorbic acid, Cu²⁺ , Mg²⁺ , Ba²⁺ , Sn²⁺ , Cr³⁺ , and K⁺ . With colloidal chitin as substrate, the K_m and the V_max of the chitinase are 4.28 mg/mL and 14.29 μg/(Min·mL), respectively, whereas the end products of the enzymatic hydrolysis are 14.33% monomer and 85.67% dimer of N-acetylglucosamine. The viscosity of carboxymethyl chitin decreased rapidly at the initial stages when subjected to chitinase hydrolysis, which indicates that the chitinase acts in an endosplitting pattern.

Characterization and diversity of the complete set of GH family 3 enzymes from Rhodothermus marinus DSM 4253

The genome of Rhodothermus marinus DSM 4253 encodes six glycoside hydrolases (GH) classified under GH family 3 (GH3): RmBgl3A, RmBgl3B, RmBgl3C, RmXyl3A, RmXyl3B and RmNag3. The biochemical function, modelled 3D-structure, gene cluster and evolutionary relationships of each of these enzymes were studied. The six enzymes were clustered into three major evolutionary lineages of GH3: β-N-acetyl-glucosaminidases, β-1,4-glucosidases/β-xylosidases and macrolide β-glucosidases. The RmNag3 with additional β-lactamase domain clustered with the deepest rooted GH3-lineage of β-N-acetyl-glucosaminidases and was active on acetyl-chitooligosaccharides. RmBgl3B displayed β-1,4-glucosidase activity and was the only representative of the lineage clustered with macrolide β-glucosidases from Actinomycetes. The β-xylosidases, RmXyl3A and RmXyl3B, and the β-glucosidases RmBgl3A and RmBgl3C clustered within the major β-glucosidases/β-xylosidases evolutionary lineage. RmXyl3A and RmXyl3B showed β-xylosidase activity with different specificities for para-nitrophenyl (pNP)-linked substrates and xylooligosaccharides. RmBgl3A displayed β-1,4-glucosidase/β-xylosidase activity while RmBgl3C was active on pNP-β-Glc and β-1,3-1,4-linked glucosyl disaccharides. Putative polysaccharide utilization gene clusters were also investigated for both R. marinus DSM 4253 and DSM 4252^T (homolog strain). The analysis showed that in the homolog strain DSM 4252^TRmar_1080 (RmXyl3A) and Rmar_1081 (RmXyl3B) are parts of a putative polysaccharide utilization locus (PUL) for xylan utilization.

Cultivation technology development of Rhodothermus marinus DSM 16675

This work presents an evaluation of batch, fed-batch, and sequential batch cultivation techniques for production of R. marinus DSM 16675 and its exopolysaccharides (EPSs) and carotenoids in a bioreactor, using lysogeny broth (LB) and marine broth (MB), respectively, in both cases supplemented with 10 g/L maltose. Batch cultivation using LB supplemented with maltose (LB_malt) resulted in higher cell density (OD₆₂₀ = 6.6) than use of MB_malt (OD₆₂₀ = 1.7). Sequential batch cultivation increased the cell density threefold (OD₆₂₀ = 20) in LB_malt and eightfold (OD₆₂₀ = 14) in MB_malt. In both single and sequential batches, the production of carotenoids and EPSs using LB_malt was detected in the exponential phase and stationary phase, respectively, while in MB_malt formation of both products was detectable in both the exponential and stationary phases of the culture. Heteropolymeric EPSs were produced with an overall volumetric productivity (Q_E) of 0.67 (mg/L h) in MB_malt and the polymer contained xylose. In LB, Q_E was lower (0.1 mg/L h) and xylose could not be detected in the composition of the produced EPSs. In conclusion, this study showed the importance of a process design and medium source for production of R. marinus DSM 16675 and its metabolites.

Thermozymes: Adaptive strategies and tools for their biotechnological applications

In today's scenario of global climate change, there is a colossal demand for sustainable industrial processes and enzymes from thermophiles. Plausibly, thermozymes are an important toolkit, as they are known to be polyextremophilic in nature. Small genome size and diverse molecular conformational modifications have been implicated in devising adaptive strategies. Besides, the utilization of chemical technology and gene editing attributions according to mechanical necessities are the additional key factor for efficacious bioprocess development. Microbial thermozymes have been extensively used in waste management, biofuel, food, paper, detergent, medicinal and pharmaceutical industries. To understand the strength of enzymes at higher temperatures different models utilize X-ray structures of thermostable proteins, machine learning calculations, neural networks, but unified adaptive measures are yet to be totally comprehended. The present review provides a recent updates on thermozymes and various interdisciplinary applications including the aspects of thermophiles bioengineering utilizing synthetic biology and gene editing tools.

Enzymatic and molecular characterization of an acidic and thermostable chitinase 1 from Streptomyces thermodiastaticus HF 3-3

Chitinase 1 (Chi1) is an acidic and thermostable hydrolytic enzyme capable of the breakdown of chitin, a resilient biopolymer that is the primary building block of fungi cell walls and marine exoskeletons. In this study, Chi1 was purified from the bacterium Streptomyces thermodiastaticus HF 3-3, and its properties were carefully characterized. The molecular mass of Chi1 was estimated to be approximately 46 kDa and, through sequencing, its N-terminal amino acid sequence was identified as ADSGKVKL. Although the optimal operating temperature and pH for Chi1 were determined to be 65°C and pH 5.5, respectively, the purified enzyme was stable over wide pH (1.5-9) and temperature ranges. Moreover, Chi1 retained 87% of its activity in the presence of 15% NaCl. While Chi1 activity was inhibited by Ag⁺ and Mn²⁺, other chemicals tested had no significant effect on its enzymatic activity. The K_m and V_max values of Chi1 for the substrate colloidal chitin were 1.23 ± 0.7 mg/mL and 6.33 ± 1.0 U/mg, respectively. Thin-layer chromatography analysis of the enzymatic reaction end products mainly detected diacetylchitobiose. We also cloned the Chi1 gene and purified the recombinant protein; the properties of the recombinant enzyme were nearly identical to those of the native enzyme. Therefore, Chi1 purified from S. thermodiastaticus HF 3-3 is unique, as it is highly stable under broad range of pH values, temperatures, and chemical exposures. Combined, these properties make this enzyme attractive for use in the industrial bioconversion of chitin.

Metagenome Analysis: a Powerful Tool for Enzyme Bioprospecting

Microorganisms are found throughout every corner of nature, and vast number of microorganisms is difficult to cultivate by classical microbiological techniques. The advent of metagenomics has revolutionized the field of microbial biotechnology. Metagenomics allow the recovery of genetic material directly from environmental niches without any cultivation techniques. Currently, metagenomic tools are widely employed as powerful tools to isolate and identify enzymes with novel biocatalytic activities from the uncultivable component of microbial communities. The employment of next-generation sequencing techniques for metagenomics resulted in the generation of large sequence data sets derived from various environments, such as soil, the human body and ocean water. This review article describes the state-of-the-art techniques and tools in metagenomics and discusses the potential of metagenomic approaches for the bioprospecting of industrial enzymes from various environmental samples. We also describe the unusual novel enzymes discovered via metagenomic approaches and discuss the future prospects for metagenome technologies.

Thermostable chitinase from Cohnella sp. A01: isolation and product optimization

Twelve bacterial strains isolated from shrimp farming ponds were screened for their growth activity on chitin as the sole carbon source. The highly chitinolytic bacterial strain was detected by qualitative cup plate assay and tentatively identified to be Cohnella sp. A01 based on 16S rDNA sequencing and by matching the key morphological, physiological, and biochemical characteristics. The cultivation of Cohnella sp. A01 in the suitable liquid medium resulted in the production of high levels of enzyme. The colloidal chitin, peptone, and K₂HPO₄ represented the best carbon, nitrogen, and phosphorus sources, respectively. Enzyme production by Cohnella sp. A01 was optimized by the Taguchi method. Our results demonstrated that inoculation amount and temperature of incubation were the most significant factors influencing chitinase production. From the tested values, the best pH/temperature was obtained at pH 5 and 70°C, with K_m and V_max values of chitinase to be 5.6mg/mL and 0.87μmol/min, respectively. Ag⁺, Co²⁺, iodoacetamide, and iodoacetic acid inhibited the enzyme activity, whereas Mn²⁺, Cu²⁺, Tweens (20 and 80), Triton X-100, and EDTA increased the same. In addition, the study of the morphological alteration of chitin treated by enzyme by SEM revealed cracks and pores on the chitin surface, indicating a potential application of this enzyme in several industries.

Genome Analysis of a New Rhodothermaceae Strain Isolated from a Hot Spring

A bacterial strain, designated RA, was isolated from water sample of a hot spring on Langkawi Island of Malaysia using marine agar. Strain RA is an aerophilic and thermophilic microorganism that grows optimally at 50–60°C and is capable of growing in marine broth containing 1–10% (w/v) NaCl. 16S rRNA gene sequence analysis demonstrated that this strain is most closely related (<90% sequence identity) to Rhodothermaceae, which currently comprises of six genera: Rhodothermus (two species), Salinibacter (three species), Salisaeta (one species), Rubricoccus (one species), Rubrivirga (one species), and Longimonas (one species). Notably, analysis of average nucleotide identity (ANI) values indicated that strain RA may represent the first member of a novel genus of Rhodothermaceae. The draft genome of strain RA is 4,616,094 bp with 3630 protein-coding gene sequences. Its GC content is 68.3%, which is higher than that of most other genomes of Rhodothermaceae. Strain RA has genes for sulfate permease and arylsulfatase to withstand the high sulfur and sulfate contents of the hot spring. Putative genes encoding proteins involved in adaptation to osmotic stress were identified which encode proteins namely Na⁺/H⁺ antiporters, a sodium/solute symporter, a sodium/glutamate symporter, trehalose synthase, malto-oligosyltrehalose synthase, choline-sulfatase, potassium uptake proteins (TrkA and TrkH), osmotically inducible protein C, and the K⁺ channel histidine kinase KdpD. Furthermore, genome description of strain RA and comparative genome studies in relation to other related genera provide an overview of the uniqueness of this bacterium.

Integrated (Meta) Genomic and Synthetic Biology Approaches to Develop New Biocatalysts

In recent years, the marine environment has been the subject of increasing attention from biotechnological and pharmaceutical industries as a valuable and promising source of novel bioactive compounds. Marine biodiscovery programmes have begun to reveal the extent of novel compounds encoded within the enormous bacterial richness and diversity of the marine ecosystem. A combination of unique physicochemical properties and spatial niche-specific substrates, in wide-ranging and extreme habitats, underscores the potential of the marine environment to deliver on functionally novel biocatalytic activities. With the growing need for green alternatives to industrial processes, and the unique transformations which nature is capable of performing, marine biocatalysts have the potential to markedly improve current industrial pipelines. Furthermore, biocatalysts are known to possess chiral selectivity and specificity, a key focus of pharmaceutical drug design. In this review, we discuss how the explosion in genomics based sequence analysis, allied with parallel developments in synthetic and molecular biology, have the potential to fast-track the discovery and subsequent improvement of a new generation of marine biocatalysts.

Purification and characterisation of an acidic and antifungal chitinase produced by a Streptomyces sp

An extremely acidic extracellular chitinase produced by a Streptomyces sp. was purified 12.44-fold by ammonium sulphate precipitation, ion-exchange chromatography and gel-permeation chromatography and further characterised. The molecular mass of the enzyme was estimated to be about 40 kDa by SDS-PAGE. The optimum pH and temperature of the purified enzyme were pH 2 and 6, and 50 °C respectively. The enzyme showed high stability in the acidic pH range of 2-6 and temperature stability of up to 50 °C. Additionally, the effect of some cations and other chemical compounds on the chitinase activity was studied. The activity of the enzyme was considerably retained under salinity conditions of up to 3%. The Km and Vmax values of the enzyme were determined to be 6.74 mg mL(-1) and 61.3 U mg(-1) respectively using colloidal chitin. This enzyme exhibited antifungal activity against phytopathogens revealing a potential biocontrol application in agriculture.

Heterologous expression, purification and biochemical characterization of endochitinase ChiA74 from Bacillus thuringiensis

ChiA74 is a secreted endochitinase produced by Bacillus thuringiensis. Previously we have partially characterized the physical parameters that affect enzymatic activity of ChiA74 in crude preparations of bacterial secretomes. In the present study, we cloned the chiA74 open reading frame (ORF) lacking the 5' sequence coding for its secretion signal peptide (chiA74Δsp) into a cold shock expression vector (pColdI) for production of the enzyme in Escherichia coli BL21-Rosetta 2. As a result, the N-terminal end of ChiA74Δsp ORF was fused to an artificial sequence of 28 amino acid, including a 6× histidine tag for purification of recombinant 6×His tagged-ChiA74Δsp (rChiA74, ∼74kDa). Along with a protein of ∼74kDa, we co-purified its ∼55kDa processed form which was confirmed by Western blot analysis. Optimal endochitinase activity of purified rChiA74 occurred at pH 7 and 40°C. Most divalent cations (e.g. Ba(+2), Ca(+2), Mn(+2), Mg(+2), Zn(+2) and Cu(+2)) at concentration of 10mM reduced chitinase activity by ∼30%, and Hg(+2) (10mM) drastically inhibited ChiA74 activity by ∼75-100%. The Vmax, Km and kcat for rChiA74 were 0.11±0.01nmol/min, 2.15μM±0.45 and 3.81s(-1), respectively, using 4-MU-GlcNAc3 as substrate. Using purified rChiA74 and colloidal chitin as substrate, chitin-derived oligosaccharides with degree of polymerization of 2 and 1 were detected.

Characterization of a thermophilic 4-O-β-D-mannosyl-D-glucose phosphorylase from Rhodothermus marinus

4-O-β-D-Mannosyl-D-glucose phosphorylase (MGP), found in anaerobes, converts 4-O-β-D-mannosyl-D-glucose (Man-Glc) to α-D-mannosyl phosphate and D-glucose. It participates in mannan metabolism with cellobiose 2-epimerase (CE), which converts β-1,4-mannobiose to Man-Glc. A putative MGP gene is present in the genome of the thermophilic aerobe Rhodothermus marinus (Rm) upstream of the gene encoding CE. Konjac glucomannan enhanced production by R. marinus of MGP, CE, and extracellular mannan endo-1,4-β-mannosidase. Recombinant RmMGP catalyzed the phosphorolysis of Man-Glc through a sequential bi-bi mechanism involving ternary complex formation. Its molecular masses were 45 and 222 kDa under denaturing and nondenaturing conditions, respectively. Its pH and temperature optima were 6.5 and 75 °C, and it was stable between pH 5.5-8.3 and below 80 °C. In the reverse reaction, RmMGP had higher acceptor preferences for 6-deoxy-D-glucose and D-xylose than R. albus NE1 MGP. In contrast to R. albus NE1 MGP, RmMGP utilized methyl β-D-glucoside and 1,5-anhydro-D-glucitol as acceptor substrates.

Vogel T, Simonet P. Soil bacterial community shifts after chitin enrichment: an integrative metagenomic approach

Chitin is the second most produced biopolymer on Earth after cellulose. Chitin degrading enzymes are promising but untapped sources for developing novel industrial biocatalysts. Hidden amongst uncultivated micro-organisms, new bacterial enzymes can be discovered and exploited by metagenomic approaches through extensive cloning and screening. Enrichment is also a well-known strategy, as it allows selection of organisms adapted to feed on a specific compound. In this study, we investigated how the soil bacterial community responded to chitin enrichment in a microcosm experiment. An integrative metagenomic approach coupling phylochips and high throughput shotgun pyrosequencing was established in order to assess the taxonomical and functional changes in the soil bacterial community. Results indicate that chitin enrichment leads to an increase of Actinobacteria, γ-proteobacteria and β-proteobacteria suggesting specific selection of chitin degrading bacteria belonging to these classes. Part of enriched bacterial genera were not yet reported to be involved in chitin degradation, like the members from the Micrococcineae sub-order (Actinobacteria). An increase of the observed bacterial diversity was noticed, with detection of specific genera only in chitin treated conditions. The relative proportion of metagenomic sequences related to chitin degradation was significantly increased, even if it represents only a tiny fraction of the sequence diversity found in a soil metagenome.

From bacteria to human: a journey into the world of chitinases

Chitinases, the enzymes responsible for the biological degradation of chitin, are found in a wide range of organisms from bacteria to higher plants and animals. They participate in numerous physiological processes such as nutrition, parasitism, morphogenesis and immunity. Many organisms, in addition to chitinases, produce inactive chitinase-like lectins that despite lacking enzymatic activity are involved in several regulatory functions. Most known chitinases belong to families 18 and 19 of glycosyl hydrolases, however a few chitinases that belong to families 23 and 48 have also been identified in recent years. In this review, different aspects of chitinases and chi-lectins from bacteria, fungi, insects, plants and mammals are discussed.

Chitinases: An update

Chitin, the second most abundant polysaccharide in nature after cellulose, is found in the exoskeleton of insects, fungi, yeast, and algae, and in the internal structures of other vertebrates. Chitinases are enzymes that degrade chitin. Chitinases contribute to the generation of carbon and nitrogen in the ecosystem. Chitin and chitinolytic enzymes are gaining importance for their biotechnological applications, especially the chitinases exploited in agriculture fields to control pathogens. Chitinases have a use in human health care, especially in human diseases like asthma. Chitinases have wide-ranging applications including the preparation of pharmaceutically important chitooligosaccharides and N-acetyl D glucosamine, preparation of single-cell protein, isolation of protoplasts from fungi and yeast, control of pathogenic fungi, treatment of chitinous waste, mosquito control and morphogenesis, etc. In this review, the various types of chitinases and the chitinases found in different organisms such as bacteria, plants, fungi, and mammals are discussed.

Optimization of nutrition factors on chitinase production from a newly isolated Chitiolyticbacter meiyuanensis SYBC-H1

The present study reports statistical medial optimization for chitinase production by a novel bacterial strain isolated from soil recently, which the name Chitinolyticbacter meiyuanensis SYBC-H1 is proposed. A sequential statistical methodology comprising of Plackett-Burman and response surface methodology (RSM) was applied to enhance the fermentative production of chitinase, in which inulin was firstly used as an effective carbon source. As a result, maximum chitinase activity of 5.17 U/mL was obtained in the optimized medium, which was 15.5-fold higher than that in the basal medium. The triplicate verification experiments were performed under the optimized nutrients levels which indicated that it well agreed with the predicted value.

Marine metagenomics: new tools for the study and exploitation of marine microbial metabolism

The marine environment is extremely diverse, with huge variations in pressure and temperature. Nevertheless, life, especially microbial life, thrives throughout the marine biosphere and microbes have adapted to all the divergent environments present. Large scale DNA sequence based approaches have recently been used to investigate the marine environment and these studies have revealed that the oceans harbor unprecedented microbial diversity. Novel gene families with representatives only within such metagenomic datasets represent a large proportion of the ocean metagenome. The presence of so many new gene families from these uncultured and highly diverse microbial populations represents a challenge for the understanding of and exploitation of the biology and biochemistry of the ocean environment. The application of new metagenomic and single cell genomics tools offers new ways to explore the complete metabolic diversity of the marine biome.

Marine metagenomics: strategies for the discovery of novel enzymes with biotechnological applications from marine environments

Metagenomic based strategies have previously been successfully employed as powerful tools to isolate and identify enzymes with novel biocatalytic activities from the unculturable component of microbial communities from various terrestrial environmental niches. Both sequence based and function based screening approaches have been employed to identify genes encoding novel biocatalytic activities and metabolic pathways from metagenomic libraries. While much of the focus to date has centred on terrestrial based microbial ecosystems, it is clear that the marine environment has enormous microbial biodiversity that remains largely unstudied. Marine microbes are both extremely abundant and diverse; the environments they occupy likewise consist of very diverse niches. As culture-dependent methods have thus far resulted in the isolation of only a tiny percentage of the marine microbiota the application of metagenomic strategies holds great potential to study and exploit the enormous microbial biodiversity which is present within these marine environments.

Mining enzymes from extreme environments

Current advances in metagenomics have revolutionized the research in fields of microbial ecology and biotechnology, enabling not only a glimpse into the uncultured microbial population and mechanistic understanding of possible biogeochemical cycles and lifestyles of extreme organisms but also the high-throughput discovery of new enzymes for industrial bioconversions. Nowadays, the genetic and enzymatic differences across the gradients from 'neutral and pristine' to 'extreme and polluted' environments are well documented. Yet, extremophilic organisms are possibly the least well understood because our ability to study and understand their metabolic potential has been hampered by our inability to isolate pure cultures. There are at least two obstacles for reaping the fruit of the microbial diversity of extremophiles: first, in spite of the recent progress in development of new culturing techniques most extremophiles cannot be cultured using traditional culturing technologies; and second, the problem of the very low biomass densities often occurs under the conditions hostile for life, which often do not yield enough DNA and reduces the effectiveness of cloning.

Characterization of a chitinolytic enzyme from Serratia sp. KCK isolated from kimchi juice

The novel chitinolytic bacterium Serratia sp. KCK, which was isolated from kimchi juice, produced chitinase A. The gene coding for the chitinolytic enzyme was cloned on the basis of sequencing of internal peptides, homology search, and design of degenerated primers. The cloned open reading frame of chiA encodes for deduced polypeptide of 563 amino acid residues with a calculated molecular mass of 61 kDa and appears to correspond to a molecular mass of about 57 kDa, which excluded the signal sequence. The deduced amino acid sequence showed high similarity to those of bacterial chitinases classified as family 18 of glycosyl hydrolases. The chitinase A is an exochitinase and exhibits a greater pH range (5.0-10.0), thermostability with a temperature optimum of 40 degrees C, and substrate range other than Serratia chitinases thus far described. These results suggested that Serratia sp. KCK chitinase A can be used for biotechnological applications with good potential.

Biotechnological aspects of chitinolytic enzymes: a review

Chitin and chitinases (EC 3.2.1.14) have an immense potential. Chitinolytic enzymes have wide-ranging applications such as preparation of pharmaceutically important chitooligosaccharides and N-acetyl D-glucosamine, preparation of single-cell protein, isolation of protoplasts from fungi and yeast, control of pathogenic fungi, treatment of chitinous waste, and control of malaria transmission. In this review, we discuss the occurrence and structure of chitin, the types and sources of chitinases, their mode of action, chitinase production, as well as molecular cloning and protein engineering of chitinases and their biotechnological applications.

Rhodothermus marinus: physiology and molecular biology

Rhodothermus marinus has been the subject of many studies in recent years. It is a thermohalophilic bacterium and is the only validly described species in the genus Rhodothermus. It is not closely related to other well-known thermophiles and is the only thermophile within the family Crenotrichaceae. R. marinus has been isolated from several similar but distantly located geothermal habitats, many of which are subject to large fluctuations in environmental conditions. This presumably affects the physiology of R. marinus. Many of its enzymes show optimum activity at temperatures considerably higher than 65 degrees C, the optimum for growth, and some are active over a broad temperature range. Studies have found distinguishing components in the R. marinus electron transport chain as well as in its pool of intracellular solutes, which accumulate during osmotic stress. The species hosts both bacteriophages and plasmids and a functional intein has been isolated from its chromosome. Despite these interesting features and its unknown genetics, interest in R. marinus has been mostly stimulated by its thermostable enzymes, particularly polysaccharide hydrolysing enzymes and enzymes of DNA synthesis which may be useful in industry and in the laboratory. R. marinus has not been amenable to genetic analysis until recently when a system for gene transfer was established. Here, we review the current literature on R. marinus.