ESTUDIO METAGENÓMICO DE LA MICROBIOTA INTESTINAL EN PACIENTES CON OBESIDAD MÓRBIDA SOMETIDOS A CIRUGÍA BARIÁTRICA / METAGENOMIC STUDY OF THE INTESTINAL MICROBIOTA IN PATIENTS WITH MORBID OBESITY UNDERGOING BARIATRIC SURGERY

Introducción: La cirugía bariátrica (CB) es un tratamiento quirúrgico de la obesidad, cuyo objetivo es lograr el descenso de peso, de masa grasa y alcanzar un impacto metabólico a largo plazo. Se ha observado que ciertos pacientes no responden tan efectivamente a la cirugía, teniendo un descenso de peso inefectivo o recuperando peso tardíamente, y los mecanismos por lo que esto ocurre aún no están bien caracterizados. La microbiota intestinal tiene un rol esencial en varios de los procesos metabólicos asociados a la obesidad. El objetivo de este estudio fue caracterizar el metagenoma intestinal de pacientes candidatos para CB y otros que fueron operados, así como también evaluar las diferencias entre aquellos pacientes que tuvieron un resultado exitoso de la CB y los que no. Material y método: Se extrajo el ADN de 200 mg de heces de pacientes que cumplen criterios de CB, divididos en 3 grupos, basal (preoperatorio), 12 meses y más de 24 meses postoperatorios, con el fin de estudiar y comparar el perfil taxonómico de las comunidades bacterianas de la microbiota intestinal. Resultados: Mientras que la riqueza específica de los grupos de estudio no presentó diferencias significativas, la diversidad beta, que considera las abundancias relativas de los miembros de las comunidades bacterianas estudiadas, evidenció una composición global significativamente diferente entre los grupos de estudio. Sin embargo, nuestro análisis no identificó taxones específicos que pudieran dar explicación a la distinta evolución postoperatoria de los pacientes. Discusión: En la estructura de las comunidades microbianas, se observaron diferencias numéricas entre los grupos en cuanto a la riqueza y abundancia de taxones así como la comparación cuanti y cualitativa. Esta última presentó significativa disimilitud. Los resultados muestran que la principal diferencia entre los grupos de estudio se basó en la abundancia relativa de los gérmenes, cuyo estudio integral podría revelar patrones más consistentes y significativos vinculados a los mecanismos de respuesta terapéutica en sujetos sometidos a CB

Introduction: Bariatric surgery (BS) is a surgical treatment of obesity, which aims to achieve weight loss, fat mass loss and achieve a long-term metabolic impact. It has been observed that certain patients do not respond as effectively to surgery, having ineffective weight loss or regaining weight late, and the mechanisms by which this occurs are not yet well characterized. The intestinal microbiota plays an essential role in several of the metabolic processes associated with obesity. The objective of our study was to characterize the intestinal metagenome of candidate patients for CB and others who underwent surgery, as well as evaluate the differences between those patients who had a successful outcome from CB and those who did not. Material and method: DNA was extracted from 200 mg of feces from patients who met the criteria for surgical indication divided into 3 groups, baseline (preoperative), 12 months and more than 24 months postoperatively, in order to analyze and compare the taxonomic profile of the bacterial communities of the intestinal microbiota. Results: While the specific richness of the study groups did not present significant differences, beta diversity, which considers the relative abundances of the members of the bacterial communities studied, showed a significantly different global composition between the study groups. Nevertheless, our study did not identify specific taxa that could explain the different postoperative evolution of the patients. Discussion: In the structure of the microbial communities, numerical differences were observed between the groups in terms of the richness and abundance of taxa as well as the quantitative and qualitative comparison. The latter evidenced significant dissimilarity. The results show that the main difference between the study groups was based on the relative abundance of the germs, whose comprehensive study could reveal more consistent and significant patterns linked to the therapeutic response mechanisms in subjects subjected to CB. Bariatric surgery (BS) is a surgical treatment of obesity, whose objective is to achieve weight loss, fat mass and achieve a longterm metabolic impact. However, it has been observed that certain patients do not respond as effectively to surgery, having ineffective weight loss or late weight regain, and the mechanisms by which this occurs are not yet well characterized. The intestinal microbiota plays an essential role in several of the metabolic processes associated with obesity. The aim of this study was to characterize the intestinal metagenome of patients who will and who underwent BS, as well as to assess the differences between those patients who had a successful BS outcome and those who did not. Our results did not identify specific taxa that could explain the different evolution of the patients. While the specific richness of the study groups did not present significant differences, the beta diversity, which considers the relative abundances of the members of the studied bacterial communities, showed a significantly different global composition between the study groups

Engineering the plastic degradation enzyme Ple629 from marine consortium to improve its thermal stability / 生物工程学报

Petrochemical-derived polyester plastics such as polyethylene terephthalate (PET) and polybutylene adipate terephthalate (PBAT) have been widely used. However, the difficulty to be degraded in nature (PET) or the long biodegradation cycle (PBAT) resulted in serious environmental pollution. In this connection, treating these plastic wastes properly becomes one of the challenges of environment protection. From the perspective of circular economy, biologically depolymerizing the waste of polyester plastics and reusing the depolymerized products is one of the most promising directions. Recent years have seen many reports on polyester plastics degrading organisms and enzymes. Highly efficient degrading enzymes, especially those with better thermal stability, will be conducive to their application. The mesophilic plastic-degrading enzyme Ple629 from the marine microbial metagenome is capable of degrading PET and PBAT at room temperature, but it cannot tolerate high temperature, which hampers its potential application. On the basis of the three-dimensional structure of Ple629 obtained from our previous study, we identified some sites which might be important for its thermal stability by structural comparison and mutation energy analysis. We carried out transformation design, and performed expression, purification and thermal stability determination of the mutants. The melting temperature (Tm) values of mutants V80C and D226C/S281C were increased by 5.2 ℃ and 6.9 ℃, respectively, and the activity of mutant D226C/S281C was also increased by 1.5 times compared with that of the wild-type enzyme. These results provide useful information for future engineering and application of Ple629 in polyester plastic degradation.

Application of nanopore sequencing in environmental microbiology research / 生物工程学报

The development of high-throughput sequencing techniques enabled a deeper and more comprehensive understanding of environmental microbiology. Specifically, the third-generation sequencing techniques represented by nanopore sequencing have greatly promoted the development of environmental microbiology research due to its advantages such as long sequencing reads, fast sequencing speed, real-time monitoring of sequencing data, and convenient machine carrying, as well as no GC bias and no PCR amplification requirement. This review briefly summarized the technical principle and characteristics of nanopore sequencing, followed by discussing the application of nanopore sequencing techniques in the amplicon sequencing, metagenome sequencing and whole genome sequencing of environmental microorganisms. The advantages and challenges of nanopore sequencing in the application of environmental microbiology research were also analyzed.

Shotgun metagenome sequencing of Chinese gut microbiota: a review / 生物工程学报

The research on the relationship between gut microbiota and human health continues to be a hot topic in the field of life science. Culture independent 16S rRNA gene high-throughput sequencing is the current main research method. However, with the reduction of sequencing cost and the maturity of data analysis methods, shotgun metagenome sequencing is gradually becoming an important method for the study of gut microbiome due to its advantages of obtaining more information. With the support from the human microbiome project, 30 805 metagenome samples were sequenced in the United States. By searching NCBI PubMed and SRA databases, it was found that 72 studies collecting about 10 000 Chinese intestinal samples were used for metagenome sequencing. To date, only 56 studies were published, including 16 related to metabolic diseases, 16 related to infectious and immune diseases, and 12 related to cardiovascular and cerebrovascular diseases. The samples were mainly collected in Beijing, Guangzhou, Shanghai and other cosmopolitan cities, where great differences exist in sequencing platforms and methods. The outcome of most studies are based on correlation analysis, which has little practical value in guiding the diagnosis and treatment of clinical diseases. Standardizing sampling methods, sequencing platform and data analysis process, and carrying out multi center parallel research will contribute to data integration and comparative analysis. Moreover, insights into the functional verification and molecular mechanism by using the combination of transcriptomics, proteomics and culturomics will enable the gut microbiota research to better serve the clinical diagnosis and treatment.

Research progress and applications of strain analysis based on metagenomic data / 生物工程学报

Strain is the fundamental unit in microbial taxonomy. The functional diversity among strains has great influence on host phenotypes. With the development of microbiome research, knowing the composition and functional capacities of complex microbial communities at the strain level has become increasingly valuable in scientific research and clinical applications. This review introduces the principles of bioinformatics algorithms for strain analysis based on metagenomic data, the applications in microbiome research and directions of future development.

Challenges and considerations on quality control and evaluation of pathogen metagenomic next-generation sequencing / 生物工程学报

Metagenomic next-generation sequencing (mNGS) could be used for pathogen detection from nearly all types of clinical samples. Especially, the unique diagnostic capability of pathogen mNGS detecting unknown causative agent of infectious diseases makes this method become an importation complement and irreplaceable component for conventional routine laboratory test. However, the complexity of the testing process, the rapid product update, and the insufficiency in quality control and evaluation methods that all make clinical transformation, industry development, and regulation of this technology full of challenge and uncertainty. This review briefly introduces the technical advantages and challenges, and describes the general workflow and quality control steps in details. Finally, it focuses on current considerations regarding quality evaluation methods and standards for pathogen mNGS.

Virome: the next hotspot in microbiome research / 生物工程学报

Virome is the collective term for the viral collection or viral metagenomes that are distributed in various environments. Viruses can be found in bodies of water, glaciers, plants, animals, and even some viruses, which are classified as eukaryotes, prokaryotes and subviruses. Viruses play very important role in maintaining environmental homeostasis and ecosystem balance, and are especially closely related to human health. In recent years, with the advancement of sequencing technology and data analysis, we are able to gain more insights into the virome and explore its potential role in the ecological niche by metagenomic sequencing. A large amount of viral data have been obtained from glaciers, oceans, and various plants and animals, and numerous unknown viruses have been discovered. Virome has been studied mainly through metagenomic data mining, as well as virus-like particles separation and enrichment. To date, several different methods for viral isolation and enrichment exist, and numerous bioinformatic analyses of the virome have been performed. However, there is a lack of specific and complete reviews on the enrichment and data analysis methods for the virome. Thus, our review will summarize viral isolation and enrichment methods and data analysis, and present some of the landmark research conducted by the enrichment method, to provide a reference for researchers of interest and further advance the field of virome research.

Preface for microbiome sequencing and analysis / 生物工程学报

Microbes are the most important commensal organisms in humans, animals and plants, and are the major habitants in soil, sediment, water, air and other habitats. The analysis of microbiome in these habitats has become a basic research technique. As a fast developing technology in recent years, microbiome sequencing and analysis have been widely used in human health, environmental pollution control, food industry, agriculture and animal husbandry and other fields. In order to sort out and summarize the current status, development and application prospects of microbiome sequencing and analysis technologies, this special issue has prepared a collection of 16 papers in this field, that comprise sample preservation and processing, single microbe genome sequencing and analysis, and microbiome feature analysis in special habitats, microbiome related databases and algorithms, and microbiome sequencing and analysis expert consensus. It also introduced in detail the development trend of the microbiome sequencing and analysis, in order to promote the rapid development of the microbiome sequencing and analysis industry and scientific research in China, and provide necessary reference for the healthy development of related industries.

Imbalance of Gut Streptococcus, Clostridium, and Akkermansia Determines the Natural Course of Atopic Dermatitis in Infant

PURPOSE: The roles of gut microbiota on the natural course of atopic dermatitis (AD) are not yet fully understood. We investigated whether the composition and function of gut microbiota and short-chain fatty acids (SCFAs) at 6 months of age could affect the natural course of AD up to 24 months in early childhood.METHODS: Fecal samples from 132 infants were analyzed using pyrosequencing, including 84 healthy controls, 22 transient AD and 26 persistent AD subjects from the Cohort for Childhood Origin of Asthma and Allergic Diseases (COCOA) birth cohort. The functional profile of the gut microbiome was analyzed by whole-metagenome sequencing. SCFAs were measured using gas chromatography-mass spectrometry.RESULTS: Low levels of Streptococcus and high amounts of Akkermansia were evident in transient AD cases, and low Clostridium, Akkermansia and high Streptococcus were found in children with persistent AD. The relative abundance of Streptococcus positively correlated with scoring of AD (SCORAD) score, whereas that of Clostridium negatively correlated with SCORAD score. The persistent AD group showed decreased gut microbial functional genes related to oxidative phosphorylation compared with healthy controls. Butyrate and valerate levels were lower in transient AD infants compared with healthy and persistent AD infants.CONCLUSIONS: Compositions, functions and metabolites of the early gut microbiome are related to natural courses of AD in infants.

Oral and Human Microbiome Research / 치위생과학회지

In the past gut microbiome has been the main focus of microbiome research. Studies about the microbiome inside oral cavities and other organs are underway. Studies about the relationship between noninfectious diseases and periodontal diseases, and the negative effects of harmful oral microbes on systemic health have been published in the recent past. A lot of attention is being paid towards fostering a healthy oral microbial ecosystem. This study aimed to understand the roles and effects of the microbiome inside the human body can potentially help cure various diseases including inflammatory bowel diseases with no known cure such as Crohn's disease, atopic dermatitis, obesity, cancer, diabetes, brain diseases and oral diseases. The present study examined technological trends in the correlation between the human microbiome and diseases in the human body, interactions between the human body's immunity, the metabolic system, and the microbiome, and research trends in other countries. While it has been proven that human microbiome is closely correlated with human diseases, most studies are still in the early stage of trying to compare the composition of microbiomes between health and patient groups. Since the oral environment is a dynamic environment that changes due to not only food intake but also other external factors such as lifestyle, hygiene, and drug intake, it is necessary to continue in-depth research on the microbiome composition characteristics to understand the complex functions of oral microorganisms. Analyzing the oral microbiome using computational technology may aid in disease diagnosis and prevention.

Oral Metagenomic Analysis Techniques / 치위생과학회지

The modern era of microbial genome analysis began in earnest in the 2000s with the generalization of metagenomics and gene sequencing techniques. Studying complex microbial community such as oral cavity and colon by a pure culture is considerably ineffective in terms of cost and time. Therefore, various techniques for genomic analysis have been developed to overcome the limitation of the culture method and to explore microbial communities existing in the natural environment at the gene level. Among these, DNA fingerprinting analysis and microarray chip have been used extensively; however, the most recent method of analysis is metagenomics. The study summarily examined the overview of metagenomics analysis techniques, as well as domestic and foreign studies on disease genomics and cluster analysis related to oral metagenome. The composition of oral bacteria also varies across different individuals, and it would become possible to analyze what change occurs in the human body depending on the activity of bacteria living in the oral cavity and what causality it has with diseases. Identification, isolation, metabolism, and presence of functional genes of microorganisms are being identified for correlation analysis based on oral microbial genome sequencing. For precise diagnosis and treatment of diseases based on microbiome, greater effort is needed for finding not only the causative microorganisms, but also indicators at gene level. Up to now, oral microbial studies have mostly involved metagenomics, but if metatranscriptomic, metaproteomic, and metabolomic approaches can be taken together for assessment of microbial genes and proteins that are expressed under specific conditions, then doing so can be more helpful for gaining comprehensive understanding.

Statistical Analysis of Metagenomics Data

Understanding the role of the microbiome in human health and how it can be modulated is becoming increasingly relevant for preventive medicine and for the medical management of chronic diseases. The development of high-throughput sequencing technologies has boosted microbiome research through the study of microbial genomes and allowing a more precise quantification of microbiome abundances and function. Microbiome data analysis is challenging because it involves high-dimensional structured multivariate sparse data and because of its compositional nature. In this review we outline some of the procedures that are most commonly used for microbiome analysis and that are implemented in R packages. We place particular emphasis on the compositional structure of microbiome data. We describe the principles of compositional data analysis and distinguish between standard methods and those that fit into compositional data analysis.

Outstanding impact of soil tillage on the abundance of soil hydrolases revealed by a metagenomic approach

ABSTRACT The soil represents the main source of novel biocatalysts and biomolecules of industrial relevance. We searched for hydrolases in silico in four shotgun metagenomes (4,079,223 sequences) obtained in a 13-year field trial carried out in southern Brazil, under the no-tillage (NT), or conventional tillage (CT) managements, with crop succession (CS, soybean/wheat), or crop rotation (CR, soybean/maize/wheat/lupine/oat). We identified 42,631 hydrolases belonging to five classes by comparing with the KEGG database, and 44,928 sequences by comparing with the NCBI-NR database. The abundance followed the order: lipases > laccases > cellulases > proteases > amylases > pectinases. Statistically significant differences were attributed to the tillage system, with the NT showing about five times more hydrolases than the CT system. The outstanding differences can be attributed to the management of crop residues, left on the soil surface in the NT, and mechanically broken and incorporated into the soil in the CT. Differences between the CS and the CR were slighter, 10% higher for the CS, but not statistically different. Most of the sequences belonged to fungi (Verticillium, and Colletotrichum for lipases and laccases, and Aspergillus for proteases), and to the archaea Sulfolobus acidocaldarius for amylases. Our results indicate that agricultural soils under conservative managements may represent a hotspot for bioprospection of hydrolases.

Comparative Analysis of Ileal and Cecal Microbiota in Aged Rats

BACKGROUND: Gut microbiota contributes to intestinal and immune homeostasis through host-microbiota interactions. Distribution of the gut microbiota differs according to the location in the gastrointestinal tract. Although the microbiota properties change with age, evidence for the regional difference of gut microbiota has been restricted to the young. The aim of this study is to compare the gut microbiota between terminal ileum and cecum of old rats. METHODS: We analyzed gut microbiome of luminal contents from ileum and cecum of 74-week-old and 2-year-old rats (corresponding to 60-year and 80-year-old of human age) by metagenome sequencing of 16S rRNA. RESULTS: Inter-individual variation (beta diversity) of microbiota was higher in ileum than in cecum. Conversely, alpha diversity of microbiota composition was higher in cecum than in ileum. Lactobacillaceae were more abundant in ileum compared to cecum while Ruminococcaceae and Lachnospiraceae were more enriched in cecum. The proportions of Deltaproteobacteria were increased in cecal microbiota of 2-year-old rats compared to 74-week-old rats. CONCLUSIONS: Major regional distinctions of microbiota between ileum and cecum of old rats appear consistent with those of young rats. Age-related alterations of gut microbiota in old rats seem to occur in minor compositions.

Recent Advances in Function-based Metagenomic Screening / 基因组蛋白质组与生物信息学报·英文版

Metagenomes from uncultured microorganisms are rich resources for novel enzyme genes. The methods used to screen the metagenomic libraries fall into two categories, which are based on sequence or function of the enzymes. The sequence-based approaches rely on the known sequences of the target gene families. In contrast, the function-based approaches do not involve the incorporation of metagenomic sequencing data and, therefore, may lead to the discovery of novel gene sequences with desired functions. In this review, we discuss the function-based screening strategies that have been used in the identification of enzymes from metagenomes. Because of its simplicity, agar plate screening is most commonly used in the identification of novel enzymes with diverse functions. Other screening methods with higher sensitivity are also employed, such as microtiter plate screening. Furthermore, several ultra-high-throughput methods were developed to deal with large metagenomic libraries. Among these are the FACS-based screening, droplet-based screening, and the in vivo reporter-based screening methods. The application of these novel screening strategies has increased the chance for the discovery of novel enzyme genes.

Increased virulence of the oral microbiome in oral squamous cell carcinoma revealed by metatranscriptome analyses / 国际口腔科学杂志·英文版

Oral squamous cell carcinoma (OSCC) is the most prevalent and most commonly studied oral cancer. However, there is a void regarding the role that the oral microbiome may play in OSCC. Although the relationship between microbial community composition and OSCC has been thoroughly investigated, microbial profiles of the human microbiome in cancer are understudied. Here we performed a small pilot study of community-wide metatranscriptome analysis to profile mRNA expression in the entire oral microbiome in OSCC to reveal molecular functions associated with this disease. Fusobacteria showed a statistically significantly higher number of transcripts at tumour sites and tumour-adjacent sites of cancer patients compared to the healthy controls analysed. Regardless of the community composition, specific metabolic signatures were consistently found in disease. Activities such as iron ion transport, tryptophanase activity, peptidase activities and superoxide dismutase were over-represented in tumour and tumour-adjacent samples when compared to the healthy controls. The expression of putative virulence factors in the oral communities associated with OSCC showed that activities related to capsule biosynthesis, flagellum synthesis and assembly, chemotaxis, iron transport, haemolysins and adhesins were upregulated at tumour sites. Moreover, activities associated with protection against reactive nitrogen intermediates, chemotaxis, flagellar and capsule biosynthesis were also upregulated in non-tumour sites of cancer patients. Although they are preliminary, our results further suggest that Fusobacteria may be the leading phylogenetic group responsible for the increase in expression of virulence factors in the oral microbiome of OSCC patients.

Human Resistome Study with Metagenomic Sequencing Data / 한양의대학술지

With the introduction of synthetic antibiotics, many lives including humans and animals have been saved against bacterial infection. An increasing level of antibiotics use, however, raises serious problems of multi-drug resistance and transferring of resistance genes across different environments and countries. Advances in high-throughput sequencing technology and efficient bioinformatics methods allow us to perform a large-scale screening and analysis of resistomes in the human and environmental microbiomes. Recent studies on human microbiomes have revealed a diverse distribution of resistance genes and their transferring activities in the communities. This review discusses recent progresses in metagenomic approaches to identify resistance genes in the human microbiome, including genomic sequence search and functional metagenomics methods. Using Rifampicin ADP-ribosyltransferase as an example, an integrative approach that analyzes the sequences and three-dimensional structures of the proteins derived from resistance genes is also introduced.

Comparison of differences in microbial compositions between negative controls and subject samples with varying analysis configurations

PURPOSE: Identifying microbial communities with 16S ribosomal RNA (rRNA) gene sequencing is a popular approach in microbiome studies, and various software tools and data resources have been developed for microbial analysis. Our aim in this study is investigating various available software tools and reference sequence databases to compare their performance in differentiating subject samples and negative controls. METHODS: We collected 4 negative control samples using various acquisition protocols, and 2 respiratory samples were acquired from a healthy subject also with different acquisition protocols. Quantitative methods were used to compare the results of taxonomy compositions of these 6 samples by varying the configuration of analysis software tools and reference databases. RESULTS: The results of taxonomy assignments showed relatively little difference, regardless of pipeline configurations and reference databases. Nevertheless, the effect on the discrepancy was larger using different software configurations than using different reference databases. In recognizing different samples, the 4 negative controls were clearly separable from the 2 subject samples. Additionally, there is a tendency to differentiate samples from different acquisition protocols. CONCLUSION: Our results suggest little difference in microbial compositions between different software tools and reference databases, but certain configurations can improve the separability of samples. Changing software tools shows a greater impact on results than changing reference databases; thus, it is necessary to utilize appropriate configurations based on the objectives of studies.

Isolation and characterization of a novel endo-beta-1, 4-glucanase from a metagenomic library of the black-goat rumen

ABSTRACT The various types of lignocellulosic biomass found in plants comprise the most abundant renewable bioresources on Earth. In this study, the ruminal microbial ecosystem of black goats was explored because of their strong ability to digest lignocellulosic forage. A metagenomic fosmid library containing 115,200 clones was prepared from the black-goat rumen and screened for a novel cellulolytic enzyme. The KG35 gene, containing a novel glycosyl hydrolase family 5 cellulase domain, was isolated and functionally characterized. The novel glycosyl hydrolase family 5 cellulase gene is composed of a 963-bp open reading frame encoding a protein of 320 amino acid residues (35.1 kDa). The deduced amino acid sequence showed the highest sequence identity (58%) for sequences from the glycosyl hydrolase family 5 cellulases. The novel glycosyl hydrolase family 5 cellulase gene was overexpressed in Escherichia coli. Substrate specificity analysis revealed that this recombinant glycosyl hydrolase family 5 cellulase functions as an endo-β-1,4-glucanase. The recombinant KG35 endo-β-1,4-glucanase showed optimal activity within the range of 30-50 °C at a pH of 6-7. The thermostability was retained and the pH was stable in the range of 30-50 °C at a pH of 5-7.

A broad pH range and processive chitinase from a metagenome library

Chitinases are hydrolases that degrade chitin, a polymer of N-acetylglucosamine linked β(1-4) present in the exoskeleton of crustaceans, insects, nematodes and fungal cell walls. A metagenome fosmid library from a wastewater-contaminated soil was functionally screened for chitinase activity leading to the isolation and identification of a chitinase gene named metachi18A. The metachi18A gene was subcloned and overexpressed in Escherichia coli BL21 and the MetaChi18A chitinase was purified by affinity chromatography as a 6xHis-tagged fusion protein. The MetaChi18A enzyme is a 92-kDa protein with a conserved active site domain of glycosyl hydrolases family 18. It hydrolyses colloidal chitin with an optimum pH of 5 and temperature of 50°C. Moreover, the enzyme retained at least 80% of its activity in the pH range from 4 to 9 and 98% at 600 mM NaCl. Thin layer chromatography analyses identified chitobiose as the main product of MetaChi18A on chitin polymers as substrate. Kinetic analysis showed inhibition of MetaChi18A activity at high concentrations of colloidal chitin and 4-methylumbelliferyl N,N′-diacetylchitobiose and sigmoid kinetics at low concentrations of colloidal chitin, indicating a possible conformational change to lead the chitin chain from the chitin-binding to the catalytic domain. The observed stability and activity of MetaChi18A over a wide range of conditions suggest that this chitinase, now characterized, may be suitable for application in the industrial processing of chitin.