Purification and characterization of cellulases produced by two Bacillus strains

Current perspective in research and industrial applications of microbial cellulases

The natural interactions between various bacteria, fungi, and other cellulolytic microorganisms destroy lignocellulosic polymers. The efficacy of this process is determined by the combined action of three main enzymes: endoglucanases, exo-glucanases, and β-glucosidase. The enzyme attacks the polymeric structure's β-1,4-linkages during the cellulose breakdown reaction. This mechanism is crucial for the environment as it recycles cellulose in the biosphere. However, there are problems with enzymatic cellulose breakdown, including complex cellulase structure, insufficient degradation efficacy, high production costs, and post-translational alterations, many of which are closely related to certain unidentified cellulase properties. These issues impede the practical use of cellulases. A developing area of research is the application of this similar paradigm for industrial objectives. Cellulase enzyme exhibits greater promise in many critical industries, including biofuel manufacture, textile smoothing and finishing, paper and pulp manufacturing, and farming. However, the study on cellulolytic enzymes must move forward in various directions, including increasing the activity of cellulase as well as designing peptides to give biocatalysts their desired attributes. This manuscript includes an overview of current research on different sources of cellulases, their production, and biochemical characterization.

Purification, Characterization, and Application of Endoglucanase from Rhizopus oryzae as Antibiofilm Agent

The enzyme endoglucanase is responsible for the depolymerization of cellulose. This study focuses on characterization and purification of endoglucanase from Rhizopus oryzae MTCC 9642 through a simple size exclusion method and its effective application as an antibiofilm agent. Extracellular ß-1,4-endoglucanase, an enzyme that catalyzes the hydrolysis of carboxymethyl cellulose, was found to be synthesized by Rhizopus oryzae MTCC 9642. The enzyme was purified up to homogeneity simply by size exclusion process through ultrafiltration and gel chromatography. The molecular weight of purified enzyme protein was estimated to be 39.8 kDa and it showed the highest substrate affinity towards carboxymethyl-cellulose with Km and Vmax values of 0.833 mg ml-1 and of 0.33 mmol glucose min-1 mg-1protein, respectively. The purified enzyme exhibited optimal activity at pH 6 with a broad stability range of pH 3-8. The most preferred temperature was 35 °C and 50% of activity could be retained after the thermal exposure at 40 °C for 25 min. The purified enzyme protein was inactivated by Cu2+, while the activity could be enhanced by the addition of exogenous thiols. Since biofilm is a challenge for health sector, with the aim of eradicating the biofilm, the purified endoglucanase was used to remove biofilm produced by two nosocomial bacteria. As predicted by in silico molecular docking interaction, the purified enzyme could effectively degrade biofilm architecture of bacterial strains S. aureus and P. aeruginosa by 76.52 ± 6.52% and 61.67 ± 8.76%, respectively. The properties of purified enzyme protein, as elucidated by in vitro and in silico characterization, may be favourable for its commercial applications as a potent antibiofilm agent.

Characterization of thermo/halo stable cellulase produced from halophilic Virgibacillus salarius BM-02 using non-pretreated biomass

The production of extremozymes from halophilic bacteria has increased significantly due to their stability and efficiency in catalyzing a reaction, as well as their capacity to display optimum activity at various salt concentrations. In the current study, the halophilic bacterium Virgibacillus salarius strain BM-02 could utilize many non-pretreated substrates including cellulose, corn stover, sugarcane bagasse and wheat bran as a sole carbon source. However, wheat bran was the best substrate for achieving optimum saccharification yield (90.1%). The partially purified cellulase was active and stable at a wide range of pH (5-8) with residual activities > 58%. Moreover, it was stable at 5-12% of NaCl. Metal ions have a variable impact on the activity of partially purified cellulase however, Fe⁺³ exhibited the highest increase in the cellulase activity. The enzyme exhibited a thermal stability at 40, 50 and 60 °C with half-lives of 1049.50, 168.14 and 163.5 min, respectively. The value of V_max was 22.27 U/mL while Km was 2.1 mM. The activation energy of denaturation E_d 69.81 kJ/mol, the enthalpy values (ΔH_d) were positive, and the entropy values (ΔS) were negative. Therefore, V. Salarius is recommended as a novel promising halophilic extremozyme producer and agricultural waste remover in the bio-industrial applications.

A Combined Study on Optimization, In Silico Modeling, and Genetic Modification of Large Scale Microbial Cellulase Production

Cellulase is a biocatalyst that hydrolyzes cellulosic biomass and is considered a major group of industrial enzymes for its applications. Extensive work has been done on microbial cellulase but fungi are considered a novel strain for their maximum cellulase production. Production cost and novel microbial strains are major challenges for its improvement where cheap agro wastes can be essential sources of cellulose as substrates. The researcher searches for more cellulolytic microbes from natural sources but the production level of isolated strains is comparatively low. So genetic modification or mutation can be employed for large-scale cellulase production before optimization. After genetic modification than in silico molecular modeling can be evaluated for substrate molecule's binding affinity. In this review, we focus not only on the conventional methods of cellulase production but also on modern biotechnological approaches applied to cellulase production by a sequential study on common cellulase-producing microbes, modified microbes, culture media, carbon sources, substrate pretreatment process, and the importance of optimum pH and temperature on fermentation. In this review, we also compare different cellulase activity determination methods. As a result, this review provides insights into the interrelationship between the characteristics of optimizing different culture conditions, genetic modification, and in silico enzyme modeling for the production of cellulase enzymes, which may aid in the advancement of large-scale integrated enzyme manufacturing of substrate-specific enzymes.

Improvement of Lignocellulolytic Enzyme Production Mediated by Calcium Signaling in Bacillus subtilis Z2 under Graphene Oxide Stress

An increase in exoenzyme production can be enhanced by environmental stresses such as graphene oxide (GO) stress, but the link between the two events is still unclear. In this work, the effect of GO as an environmental stress factor on exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) biosynthesis was investigated in Bacillus subtilis Z2, and a plausible mechanism by which cytosolic Ca²⁺ regulates lignocellulolytic enzyme production in B. subtilis Z2 subjected to GO stress was proposed. The filter paper-hydrolyzing (FPase [representing total cellulase]), carboxymethylcellulase (CMCase [representing endoglucanase]), and β-glucosidase activities and extracellular protein concentration of the wild-type strain under 10 μg/mL GO stress were 1.37-, 1.64-, 1.24-, and 1.16-fold those of the control (without GO stress), respectively. Correspondingly, the transcription levels of lignocellulolytic enzyme genes, cytosolic Ca²⁺ level, and biomass concentration of B. subtilis were all increased. With lignocellulolytic enzyme from B. subtilis used to hydrolyze alkali-pretreated rice straw, the released reducing sugar concentration reached 265.53 mg/g, and the removal rates of cellulose, hemicellulose, and lignin were 52.4%, 30.1%, and 7.5%, respectively. Furthermore, transcriptome data revealed that intracellular Ca²⁺ homeostasis played a key role in regulating the levels of gene transcription related to the synthesis of lignocellulolytic enzymes and exoenzymes. Finally, the use of Ca²⁺ inhibitors (LaCl₃ and EDTA) and deletion of spcF (a calmodulin-like protein gene) further demonstrated that the overexpression of those genes was regulated via calcium signaling in B. subtilis subjected to GO stress. IMPORTANCE To effectively convert lignocellulose into fermentable sugars, high lignocellulolytic enzyme loading is needed. Graphene oxide (GO) has been shown to promote exoenzyme (lignocellulolytic enzyme, amylase, peptidase, and protease) production in some microorganisms; however, the regulatory mechanism of the biosynthesis of lignocellulolytic enzymes under GO stress remains unclear. In this work, the lignocellulolytic enzyme production of B. subtilis under GO stress was investigated, and the potential mechanism by which B. subtilis enhanced lignocellulolytic enzyme production through the calcium signaling pathway under GO stress was proposed. This work revealed the role of calcium signaling in the production of enzymes under external environmental stress and provided a direction to facilitate lignocellulolytic enzyme production by B. subtilis.

Screening of Cellulolytic Bacteria from Various Ecosystems and Their Cellulases Production under Multi-Stress Conditions

Cellulose represents the most abundant component of plant biomass on earth; it is degraded by cellulases, specific enzymes produced by microorganisms. However, cellulases of bacterial origin attract more interest due to their natural diversity and ability to inhabit a variety of niches, allowing the selection of cellulolytic strains resistant to environmental stresses. The screening of the cellulolytic activity of 398 bacteria isolated from various ecosystems in Algeria (cave, ruins, chott, thermal station, and rhizosphere of arid and semi-arid regions) was performed by the appearance of a hydrolysis zone on carboxymethylcellulose (CMC) medium. The cellulase activity on CMC (1%) broth allowed to select 26 strains among which 12 had the best activity (0.3 U/mL to 2.2 U/mL). Optimization of physicochemical parameters (salinity: 0–1 M NaCl; pH: 3, 4, 7, 9, and 11; temperature: 30, 45, and 50 °C; PEG8000: 0 and 30%) involved in growth and cellulose production showed that the majority of strains were mesophilic, neutrophilic, or alkali- tolerant and tolerant to 30% of PEG8000. The cellulase activity and stability under different stress allowed to retain five strains, which the most efficient. Based on the 16S-rRNA sequencing results, they belonged to the genus Bacillus. The physicochemical properties of cellulases (crude extract) showed a CMCase active over a wide range of pH (4 to 11), optimal at 50 °C and 60 °C. The inhibiting salinity effect on the activity was not detected and was negligible on the enzymatic stability. The residual CMCase activity remained between 40 and 70% in a temperature range between 40 and 70 °C, was stable over a wide range of saline concentrations (0–2000 mM), and was weakly affected at 30% of PEG8000. The crude enzyme extract was able to hydrolyze both soluble and insoluble cellulosic substrates. The evaluation of the hydrolysis capacity of lignocellulosic waste revealed the ability of tested strains to degrade wheat bran, barley bran, and corncob. In addition, the enzyme showed significant multi-stress resistance on solid and liquid media. By these characteristics, these cellulolytic bacteria could be attractive to be used in various industrial and biotechnology applications.

Expression, characterization, and activity optimization of a novel cellulase from the thermophilic bacteria Cohnella sp. A01

Cellulases are hydrolytic enzymes with wide scientific and industrial applications. We described a novel cellulase, CelC307, from the thermophilic indigenous Cohnella sp. A01. The 3-D structure of the CelC307 was predicted by comparative modeling. Docking of CelC307 with specific inhibitors and molecular dynamic (MD) simulation revealed that these ligands bound in a non-competitive manner. The CelC307 protein was purified and characterized after recombinant expression in Escherichia coli (E. coli) BL21. Using CMC 1% as the substrate, the thermodynamic values were determined as K_m 0.46 mM, k_cat 104.30 × 10^-3 (S^-1), and k_cat/K_m 226.73 (M^-1 S^-1). The CelC307 was optimally active at 40 °C and pH 7.0. The culture condition was optimized for improved CelC307 expression using Plackett-Burman and Box-Behnken design as follows: temperature 20 °C, pH 7.5, and inoculation concentration with an OD₆₀₀ = 1. The endoglucanase activity was positively modulated in the presence of Na⁺, Li⁺, Ca²⁺, 2-mercaptoethanol (2-ME), and glycerol. The thermodynamic parameters calculated for CelC307 confirmed its inherent thermostability. The characterized CelC307 may be a suitable candidate for various biotechnological applications.

Production Optimization and Biochemical Characterization of Cellulase from Geobacillus sp. KP43 Isolated from Hot Spring Water of Nepal

This study is aimed at isolating and identifying a thermophilic cellulolytic bacterium from hot spring water and characterizing thermostable cellulase produced by the isolate. Enrichment and culture of water sample was used for isolation of bacterial strains and an isolate with highest cellulase activity was chosen for the production, partial purification, and biochemical characterization of the enzyme. Different staining techniques, enzymatic tests, and 16s ribosomal DNA (16s rDNA) gene sequencing were used for the identification of the isolate. The cellulase producing isolate was Gram positive, motile, and sporulated rod-shaped bacterium growing optimally between 55°C and 65°C. Based on partial 16s rDNA sequence analysis, the isolate was identified as Geobacillus sp. and was designated as Geobacillus sp. KP43. The cellulase enzyme production condition was optimized, and the product was partially purified and biochemically characterized. Optimum cellulase production was observed in 1% carboxymethyl cellulose (CMC) at 55°C. The molecular weight of the enzyme was found to be approximately 66 kDa on 12% SDS-PAGE analysis. Biochemical characterization of partially purified enzyme revealed the temperature optimum of 70°C and activity over a wide pH range. Further, cellulase activity was markedly stimulated by metal ion Fe^2+. Apart from cellulases, the isolate also depicted good xylanase, cellobiase, and amylase activities. Thermophilic growth with a variety of extracellular enzyme activities at elevated temperature as well as in a wide pH range showed that the isolated bacteria, Geobacillus sp. KP43, can withstand the harsh environmental condition, which makes this organism suitable for enzyme production for various biotechnological and industrial applications.

Purification, biochemical characterization, and molecular cloning of cellulase from Bacillus licheniformis strain Z9 isolated from soil

Background

Cellulose is the most prevalent biomass and renewable energy source in nature. The hydrolysis of cellulosic biomass to glucose units is essential for the economic exploitation of this natural resource. Cellulase enzyme, which is largely generated by bacteria and fungus, is commonly used to degrade cellulose. Cellulases are used in a variety of industries, including bioethanol manufacturing, textiles, detergents, drugs, food, and paper. As part of our quest to find an efficient biocatalyst for the hydrolysis of cellulosic biomass, we describe the amplification, cloning, and sequencing of cellulase (cel9z) from Bacillus licheniformis strain Z9, as well as the characterization of the resulting enzyme.

Results

Cellulase was partially purified from B. licheniformis strain Z9 using (NH₄)₂SO₄ precipitation and Sephadex G-100 gel column chromatography with 356.5 U/mg specific activity, 2.1-purification fold, and 3.07 % yield. The nucleotide sequence of the cellulase gene was deposited to the GenBank, B. licheniformis strain Z9 cellulase (cel9z) gene, under accession number MK814929. This corresponds to 1453 nucleotides gene and encodes for a protein composed of 484 amino acids. Comparison of deduced amino acids sequence to other related cellulases showed that the enzyme cel9z can be classified as a glycoside hydrolase family 9. SDS-PAGE analysis of the purified enzyme revealed that the molecular mass was 54.5 kDa. The optimal enzyme activity was observed at pH 7.4 and 30 °C. The enzyme was found to be strongly inhibited by Mg²⁺ and Na⁺, whereas strongly activated by Fe³⁺, Cu²⁺, and Ca²⁺.

Conclusions

B. licheniformis strain Z9 and its cellulase gene can be further utilized for recombinant production of cellulases for industrial application.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00317-4.

Biological approach in deinking of waste paper using bacterial cellulase as an effective enzyme catalyst

Paper has become the basic elixir in everyone's activities and usage of paper has increased day by day, the waste generated by paper is also enormous. The primary source of paper is wood (tree) yet, waste paper is environmentally good and biodegradable; however, it is the primary source of deforestation. Current research aims to find an alternate way to recycle paper in the biological approach. Hence in our work, twelve cellulose-producing bacteria were isolated, out of which one bacterial strain proved to be the best. Cellulase enzyme was extracted and purified, and used for enzymatic de-inking of photocopy papers. The optimal conditions for cellulase synthesis were at 60 °C, glucose as the only carbon source, and potassium nitrate as the nitrogen source. The enzyme demonstrated excellent de-inking at a lower pulp consistency of 3% with a 20% enzyme dose. The cellulose and hemicellulose levels decreased, which can be attributed to fiber breaking. Further, the changes in the functional groups identified by Fourier-transform infrared spectroscopy analysis and the changes in the surface morphology of the pulp fibers were obtained using scanning electron microscope analysis.

Kinetics of aerobic cellulose degradation in raw municipal wastewater

Cellulose contributes approximately one third of the influent suspended solids to wastewater treatment plants and is a key target for resource recovery. This study investigated the temperature impact on biological aerobic degradation of cellulose in laboratory-scale sequencing batch reactors (SBR) at four different temperatures (10-33 °C) and two different solids retention times (SRT) of 15 days and 3 days. The degradation efficiency of cellulose was observed to increase with temperature and was slightly dependent on SRT (80%-90% at an SRT of 15 days, and 78%-85% at an SRT of 3 days). Hydrolysis followed 1st order kinetics, rather than the biomass dependent Contois kinetics (default in the activated sludge models), with a hydrolysis coefficient at 20 °C of 1.14 ± 0.01 day^-1.

Fermentation optimization of cellulase production from sugarcane bagasse by Bacillus pseudomycoides and molecular modeling study of cellulase

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Isolation of cellulase producing Bacillus pseudomycoides from sugarcane bagasse.

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Fermentation and optimization of different parameters for cellulase production.

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Modeling and validation of cellulase enzyme.

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Interaction dynamics between cellulase and cellulose.

Degradation of cellulosic carbon, the most important natural carbon reservoirs on this planet by cellulase is very essential for valuable soluble sugars. This cellulase has potential biotechnological applications in many industrial sectors. Thus the demand of cellulase is increasing more frequently than ever. Agro industrial byproducts and suitable microbes are of an important source for the production of cellulase. Bacillus pseudomycoides and sugarcane bagasse were used for the production of cellulase and different process parameters influencing the production of cellulase were optimized here. The bacterium showed maximum cellulase production in the presence of sugarcane bagasse, peptone and magnesium sulfate at pH 7, 40 °C in 72 h of incubation. Primary structures of the cellulase is consists of 400 amino acid residues having molecular weight 44,790 Dalton and the theoretical PI is 9.11. Physiochemical properties of cellulase indicated that the protein has instability index 25.77. Seven hydrogen bonds were observed at multiple sites of the cellulase enzyme; His269, Asp237, Asn235, Tyr271, Ser272, Gln309, Asn233. This protein structure may play first hand in further development of exploring cellulase and cellulose interaction dynamics in Bacillus sp. Thus this bacterium may be useful in various industrial applications owing to its cellulase producing capability.

Expression and functional characterization in yeast of an endoglucanase from Bacillus sonorensis BD92 and its impact as feed additive in commercial broilers

Some ingredients used in poultry feed formulation contain carbohydrate polymers which are difficult to digest and thus hinder nutritional feed value. Toward overcoming this limitation, exogenous enzymes have been added to poultry feed to improve its nutritive value. The present study was designed to provide first enzymatic characterization of endoglucanase (BsEgl) from the genome of B. sonorensis BD92 expressed in Pichia pastoris. Further, we tested its impact alone and in combination with a β-glucosidase (Bteqβgluc) on growth in commercial broilers as feed additive. The expressed enzyme displayed features of GH5 family and had optimum activity against carboxymethyl cellulose at pH 5 and 50 °C. The BsEgl was stable at a range of pH from 4 to 8 for 60 min and at 50 °C for 180 min. Supplementing broilers diet with BsEgl alone or in combination with Bteqβgluc resulted in better feed conversion ratio among treatments during a five weeks testing period. Moreover, meat percentage was also highest for this treatment, and all treatments with recombinant enzymes increased intestinal length in birds compared to treatment control group. Blood parameters and serum biochemistry profile showed non-significant difference among groups. These results support that recombinant cellulolytic enzymes supplement high fiber diets improve their nutritional performance.

Isolation, Identification and In Silico Study of Native Cellulase Producing Bacteria

Aims:

The purpose of this study was to screen the bacteria producing cellulase enzymes and their bioinformatics studies.

Background:

Cellulose is a long-chain polymer of glucose that hydrolyzes by cellulases to glucose molecules. In order to design the new biotechnological applications, some strategies have been used as increasing the efficiency of enzyme production, generating cost-effective enzymes, producing stable enzymes and identification of new strains.

Objective:

On the other hand, some bacteria special features have made them suitable candidates for the identification of the new source of enzymes. In this regard, some native strains of bacteria were screened.

Methods:

These bacteria were grown on a culture containing the liquid M9 media containing CMC to ensure the synthesis of cellulase. The formation of a clear area in the culture medium indicated decomposition of cellulose. In the following, the DNA of these bacteria were extracted and their 16S rDNA genes were amplified.

Result:

The results show that nine samples were able to synthesize cellulase. In following, these strains were identified using 16S rDNA. The results show that these screened bacteria belonged to the Bacillus sp., Alcaligenes sp., Alcaligenes sp., and Enterobacter sp.

Conclusion:

The enzyme activity analysis shows that the Bacillus toyonensis, Bacillus sp. strain XA15-411 Bacillus cereus have produced the maximum yield of cellulases. However, these amounts of enzyme production in these samples are not proportional to their growth rate. As the bacterial growth chart within 4 consecutive days shows that the Alcaligenes sp. Bacillus cereus, Bacillus toyonensis, Bacillus sp. strain XA15-411 have a maximum growth rate. The study of the phylogenetic tree also shows that Bacillus species are more abundant in the production of cellulase enzyme. These bioinformatics analyses show that the Bacillus species have different evolutionary relationships and evolved in different evolutionary time. However, for maximum cellulase production by this bacteria, some information as optimum temperature, optimum pH, carbon and nitrogen sources are needed for the ideal formulation of media composition. The cellulase production is closely controlled in microorganisms and the cellulase yields appear to depend on a variety of factors. However, the further studies are needed for cloning, purification and application of these new microbial cellulases in the different commercial fields as in food, detergent, and pharmaceutical, paper, textile industries and also various chemical industries. However, these novel enzymes can be further engineered through rational design or using random mutagenesis techniques.

Isolation, purification and characterization of cellulase produced by Aspergillus niger cultured on Arachis hypogaea shells

Cellulases are enzymes that hydrolyse cellulose and related cellu-oligosaccharides derivatives. Its applications are enormous but high cost of production is the bottle-neck against the utilization of cellulase in industries. Therefore, this study investigated the isolation, purification and characterization of cellulase produced by Aspergillus niger cultured on Arachis hypogaea shells. The crude cellulase enzyme was produced by A. niger through submerged fermentation process using A. hypogaea shells as a carbon source. The optima fermentation conditions were determined by varying different parameters. The crude cellulase was purified through ammonium sulphate precipitation, dialysis and gel-filtration chromatography. The molecular weight was estimated using sodium dodecyl sulphate polyacrylamide gel electrophoresis. The effects of pH and temperature on the activity of the purified cellulase were investigated. The study revealed that the: optimal production of crude cellulase was achieved at incubation period of 120 h, pH 4, temperature 40 °C, and inoculum size of 13 × 10⁵ CFU/ml. Cellulase was purified to 68.12-fold with a yield and specific activity of 3.87% and 484.3 U/mg respectively. The V_max for the cellulase was 9.26 U/ml while the K_m was 0.23 mg/ml. The molecular weight of the cellulase was approximately 13.5 kDa and the enzyme has higher specificity for CMC compared to other substrates. The optimum pH and temperature for the cellulase activity were 4 and 40 °C respectively. The present study has shown that A. hypogaea shells can be used as a carbon source by A. niger for the production of cellulase.

Production of Highly Active Extracellular Amylase and Cellulase From Bacillus subtilis ZIM3 and a Recombinant Strain With a Potential Application in Tobacco Fermentation

In this study, a series of bacteria capable of degrading starch and cellulose were isolated from the aging flue-cured tobacco leaves. Remarkably, there was a thermophilic bacterium, Bacillus subtilis ZIM3, that can simultaneously degrade both starch and cellulose at a wide range of temperature and pH values. Genome sequencing, comparative genomics analyses, and enzymatic activity assays showed that the ZIM3 strain expressed a variety of highly active plant biomass-degrading enzymes, such as the amylase AmyE1 and cellulase CelE1. The in vitro and PhoA-fusion assays indicated that these enzymes degrading complex plant biomass into fermentable sugars were secreted into ambient environment to function. Besides, the amylase and cellulase activities were further increased by three- to five-folds by using overexpression. Furthermore, a fermentation strategy was developed and the biodegradation efficiency of the starch and cellulose in the tobacco leaves were improved by 30–48%. These results reveal that B. subtilis ZIM3 and the recombinant strain exhibited high amylase and cellulase activities for efficient biodegradation of starch and cellulose in tobacco and could potentially be applied for industrial tobacco fermentation.

Effects of submerged liquid fermentation of Bacillus subtilis WX-17 using okara as sole nutrient source on the composition of a potential probiotic beverage

This work aims to produce a functional probiotic beverage using okara as the sole nutrient source. Hence, okara was fermented with Bacillus subtilis WX-17 in submerged liquid fermentation and the supernatant was tested. Metabolomic analysis showed that the nutritional profile of the beverage was enhanced after fermentation. Essential amino acids as well as short-chain fatty acids were significantly (p < .05) upregulated. Total phenolic content and antioxidant content (in terms of DPPH radical scavenging activity) increased by 6.32 and 1.55 times, respectively. After 6 weeks, probiotic viability remains unchanged when stored at 4°C and the cell count is above the minimum dosage to confer health benefits. Antimicrobial activity was also detected against gram-positive bacteria. The findings of this work showed the potential of submerged liquid fermentation of Bacillus subtilis WX-17 using okara as sole substrate to produce a functional and low-cost probiotic beverage.

Semi-continuous fermentation of solid waste in closed artificial ecosystem: Microbial diversity, function genes evaluation

Bioregenerative Life Support System (BLSS) is a closed artificial ecosystem and could provide oxygen, food, water and other substances for space survival. Solid waste treatment is a key rate-limiting step in BLSS. In this study, solid wastes including wheat straw, human and yellow mealworm feces were disposed in a semi-continuous bio-convertor for 105 days in a ground-based experimental BLSS platform (Lunar Palace 1). Solid wastes at different periods were sampled and the microbial community variation, functional genes and metabolic pathways were analyzed. The results showed phyla Firmicutes, Bacteroidetes and Proteobacteria predominated in all samples. While microbial community structures at genus level were significantly different, indicating selective enrichment during the 105-day process. The abundance of functional gene related to carbohydrate transport and metabolism was predicted higher on 45-day and 70-day. The metabolic pathway analysis revealed the degradation mechanisms and provided evidence for metabolic regulation.

Thermostable endoglucanase gene derived by amplification from the genomic DNA of a cellulose-enriched mixed culture from mudspring water of Mt. Makiling, Laguna, Philippines

Culture-independent molecular-based approaches can be used to identify genes of interest from environmental sources that have desirable properties such as thermo activity. For this study, a putative thermo stable endoglucanase gene was identified from a mixed culture resulting from the inoculation of Brock-CMcellulose (1%) broth with mudspring water from Mt. Makiling, Laguna, Philippines that had been incubated at 90 °C. Genomic DNA was extracted from the cellulose-enriched mixed culture and endo1949 forward and reverse primers were used to amplify the endoglucanase gene, which was cloned into pCR-script plasmid vector. Blastn alignment of the sequenced insert revealed 99.69% similarity to the glycosyl hydrolase, sso1354 (CelA1; Q97YG7) from Saccharolobus solfataricus. The endoglucanase gene (GenBank accession number MK984682) was determined to be 1,021 nucleotide bases in length, corresponding to 333 amino acids with a molecular mass of ~ 37 kDa. The endoglucanase gene was inserted into a pET21 vector and transformed in E. coli BL21 for expression. Partially purified recombinant Mt. Makiling endoglucanase (MM-Engl) showed a specific activity of 187.61 U/mg and demonstrated heat stability up to 80 °C. The thermo-acid stable endoglucanase can be used in a supplementary hydrolysis step to further hydrolyze the lignocellulosic materials that were previously treated under high temperature-dilute acid conditions, thereby enhancing the release of more glucose sugars for bioethanol production.

Comparative Analysis of Structural Variations Due to Genome Shuffling of Bacillus Subtilis VS15 for Improved Cellulase Production

Cellulose is one of the most abundant and renewable biomass products used for the production of bioethanol. Cellulose can be efficiently hydrolyzed by Bacillus subtilis VS15, a strain isolate obtained from decomposing logs. A genome shuffling approach was implemented to improve the cellulase activity of Bacillus subtilis VS15. Mutant strains were created using ethyl methyl sulfonate (EMS), N-Methyl-N′ nitro-N-nitrosoguanidine (NTG), and ultraviolet light (UV) followed by recursive protoplast fusion. After two rounds of shuffling, the mutants Gb2, Gc8, and Gd7 were produced that had an increase in cellulase activity of 128%, 148%, and 167%, respectively, in comparison to the wild type VS15. The genetic diversity of the shuffled strain Gd7 and wild type VS15 was compared at whole genome level. Genomic-level comparisons identified a set of eight genes, consisting of cellulase and regulatory genes, of interest for further analyses. Various genes were identified with insertions and deletions that may be involved in improved celluase production in Gd7. Strain Gd7 maintained the capability of hydrolyzing wheatbran to glucose and converting glucose to ethanol by fermentation with Saccharomyces cerevisiae of the wild type VS17. This ability was further confirmed by the acidified potassium dichromate (K₂Cr₂O₇) method.

Comparative Study of Extracellular Proteolytic, Cellulolytic, and Hemicellulolytic Enzyme Activities and Biotransformation of Palm Kernel Cake Biomass by Lactic Acid Bacteria Isolated from Malaysian Foods

Biotransformation via solid state fermentation (SSF) mediated by microorganisms is a promising approach to produce useful products from agricultural biomass. Lactic acid bacteria (LAB) that are commonly found in fermented foods have been shown to exhibit extracellular proteolytic, β-glucosidase, β-mannosidase, and β-mannanase activities. Therefore, extracellular proteolytic, cellulolytic, and hemicellulolytic enzyme activities of seven Lactobacillus plantarum strains (a prominent species of LAB) isolated from Malaysian foods were compared in this study. The biotransformation of palm kernel cake (PKC) biomass mediated by selected L. plantarum strains was subsequently conducted. The results obtained in this study exhibited the studied L. plantarum strains produced versatile multi extracellular hydrolytic enzyme activities that were active from acidic to alkaline pH conditions. The highest total score of extracellular hydrolytic enzyme activities were recorded by L. plantarum RI11, L. plantarum RG11, and L. plantarum RG14. Therefore, they were selected for the subsequent biotransformation of PKC biomass via SSF. The hydrolytic enzyme activities of treated PKC extract were compared for each sampling interval. The scanning electron microscopy analyses revealed the formation of extracellular matrices around L. plantarum strains attached to the surface of PKC biomass during SSF, inferring that the investigated L. plantarum strains have the capability to grow on PKC biomass and perform synergistic secretions of various extracellular proteolytic, cellulolytic, and hemicellulolytic enzymes that were essential for the effective biodegradation of PKC. The substantial growth of selected L. plamtraum strains on PKC during SSF revealed the promising application of selected L. plantarum strains as a biotransformation agent for cellulosic biomass.

Industrial attributes of β-glucanase produced by Bacillus sp. CSB55 and its potential application as bio-industrial catalyst

The β-glucanase produced from Bacillus sp. CSB55 not only depicts the potent industrial characteristics but also relates as bio-industrial catalyst supporting the spontaneous formation of the products, high hydrolytic efficiency, and feasibility of the enzymatic reaction. A homogeneous β-glucanase (GluB55) was purified via various purification processes resulting in 11.69% yield and 14.24-fold purity. Biochemical characterization of the purified enzyme revealed the molecular mass of approximately 40 kDa, which was verified by zymography. The optimum activity of GluB55 was determined at pH 7.2 and 55 °C. GluB55 could highly hydrolyze carboxymethylcellulose and was stable over a wide range of pH, retaining more than 70% residual activity at pH 5.8-11.0 and carried 100% thermostability as high as 60 °C. In addition, it showed 68% residual activity at 70 °C. The N-terminal amino acid sequence of GluB55 was Ala-Asn-Pro-Glu-Leu-Val-Asn-X-Gln-Ala-X-X-Ala-X-Gln-Gly. The enzyme activity was stimulated by Co²⁺ (158.6%), Zn²⁺ (211.1%), Mn²⁺ (264.4%), and Ba²⁺ (211.4%). Enzyme kinetics showed K_m and V_max values of 0.022 mg mL^-1 and 994.56 ± 3.72 U mg^-1, respectively. Q₁₀ was calculated to be 1.12. ∆H, ∆G, and ∆S were low revealing that the formation of the transition phase and conversion to the product is very well organized. The lower the free energy change (∆G), the more feasible is the reaction.

A novel beta-1,4 glucanase produced by symbiotic Bacillus sp. CF96 isolated from termite (Anacanthotermes)

A novel beta-1,4-glucanase was purified and characterized from symbiotic Bacillus sp. CF96 of termite. The SDS-PAGE and zymogram analyses revealed a molecular mass of 35.6 kDa. Optimal activity was at 50 °C and pH 5.5, while the enzyme was active over a wide range of temperature 20-80 °C and pH 4-10 and interestingly more than 60% of the maximum activity remained up to pH 9. The enzyme activity increased in the presence of hexane, chloroform and methanol (20% v/v). while, the enzyme activity was inhibited by metal ions such as Mn²⁺, Hg²⁺, Cu²⁺, Zn²⁺, Mg²⁺, Fe²⁺. The isolated enzyme was able to degrade carboxymethyl cellulose (CMC), avicel and cellulose. Cellobiose was the hydrolytic product of enzymatic reaction based on thin layer chromatography (TLC) analysis. Regarding beta-1,4 endo/exoglucanase activity and high temperature, pH and solvent stability, the enzyme has potential for various industrial applications especially in designing pesticide for termite.

Isolation and Partial Characterisation of Thermophilic Cellulolytic Bacteria from North Malaysian Tropical Mangrove Soil

This study reports the biodiversity of thermophilic cellulolytic bacterial strains that present in the north Malaysian mangrove ecosystem. Soil samples were collected at the four most northern state of Malaysia (Perak, Pulau Pinang, Kedah and Perlis). The samples obtained were first enriched in nutrient broth at 45°C and 55°C prior culturing in the carboxymethylcellulose (CMC) agar medium. Repeated streaking was performed on the CMC agar to obtain a pure culture of each isolate prior subjecting it to hydrolysis capacity testing. The isolates that showing the cellulolytic zone (halozone) were sent for 16S rRNA sequencing. Total seven isolates (two from Perak, three from Kedah, another two were from Perlis and Penang each) showed halozone. The isolate (KFX-40) from Kedah exhibited highest halozone of 3.42 ± 0.58, meanwhile, the one obtained from Perak (AFZ-0) showed the lowest hydrolysis capacity (2.61 ± 0.10). Based on 16S rRNA sequencing results, 5 isolates (AFY-40, AFZ-0, KFX-40, RFY-20, and PFX-40) were determined to be Anoxybacillus sp. The other two isolates were identified as Bacillus subtilis (KFY-40) and Paenibacillus dendritiformis (KFX-0). Based on growth curve, doubling time of Anoxybacillus sp. UniMAP-KB06 was calculated to be 32.3 min. Optimal cellulose hydrolysis temperature and pH of this strain were determined to be 55°C and 6.0 respectively. Addition of Mg²⁺ and Ca²⁺ were found to enhance the cellulase activity while Fe³⁺ acted as an enzyme inhibitor.

Bioprospecting thermophilic glycosyl hydrolases, from hot springs of Himachal Pradesh, for biomass valorization

The harnessing of biocatalysts from extreme environment hot spring niche for biomass conversion is significant and promising owing to the special characteristics of extremozymes attributed by intriguing biogeochemistry and extreme conditions of these environments. Hence, in the present study 38 bacterial isolates obtained from hot springs of Manikaran (~ 95 °C), Kalath (~ 50 °C) and Vasist (~ 65 °C) of Himachal Pradesh were screened for glycosyl hydrolases by in situ enrichment technique using lignocellulosic biomass (LCB). Based on their hydrolytic potential 5 isolates were selected and they were Bacillus tequilensis (VCB1, VCB2 and VSDB4), and B. licheniformis (KBFB2 and KBFB3). Cellulolytic activity assayed by growth under submerged fermentation showed that B. tequilensis VCB1 had maximum FPA activity (3.38 IU ml⁻¹) in 48 h, while B. licheniformis KBFB3 excelled for endoglucanase (EGA of 4.81 IU ml⁻¹ in 24 h) and cellobiase (0.71 IU ml⁻¹ in 48 h) activities. Among all the thermophilic biocatalysts evaluated, highest exoglucanase (0.06 IU ml⁻¹) activity was observed in B. tequilensis VSDB4 while endoglucanase of B. licheniformis KBFB3 showed optimum specific activity at pH 7 and 70 °C. Further, the presence of celS, celB and xlnB genes in the isolates suggest their possible role in biomass conversion. Protein profiling by SDS-PAGE analysis revealed that cellulase isoforms migrated with molecular masses of 75 kDa. The endoglucanase activity of promising strain B. licheniformis KBFB3 was enhanced in the presence of Ca²⁺, mercaptoethanol and sodium hypochlorite whereas moderately inhibited by Cu²⁺, Zn²⁺, urea, SDS and H₂O₂. The results of this study indicate scope for the possible development of novel biocatalysts with multifunctional thermostable glycosyl hydrolases from hot springs for efficient hydrolysis of the complex lignocellulosic biomass into simple sugars and other derived bioproducts leading to biomass valorization.

Conversion of stranded waste-stream carbon and nutrients into value-added products via metabolically coupled binary heterotroph-photoautotroph system

Growth of heterotrophic bacterium Bacillus subtilis was metabolically coupled with the photosynthetic activity of an astaxanthin-producing alga Haematococcus pluvialis for conversion of starch-containing waste stream into carotenoid-enriched biomass. The H. pluvialis accounted for 63% of the produced co-culture biomass of 2.2 g/L. Importantly, the binary system requires neither exogenous supply of gaseous substrates nor application of energy-intensive mass transfer technologies due to in-situ exchange in CO₂ and O₂. The maximum reduction in COD, total nitrogen and phosphorus reached 65%, 55% and 30%, respectively. Conducted techno-economic assessment suggested that the astaxanthin-rich biomass may potentially offset the costs of waste treatment, and, with specific productivity enhancements (induction of astaxanthin to 2% and increase H. pluvialis fraction to 80%), provide and additional revenue stream. The outcome of this study demonstrates a successful proof-of-principle for conversion of waste carbon and nutrients into value-added products through metabolic coupling of heterotrophic and phototrophic metabolisms.

Isolation of bacteria from fermented food and grass carp intestine and their efficiencies in improving nutrient value of soybean meal in solid state fermentation

Background

Soybean meal is an excellent and cost-effective protein source; however, its usage is limited in the piglet due to the presence of anti-nutritional factors and the antigens glycinin and β-conglycinin. The objective of the current study was to screen and select for bacteria that can be efficiently adopted to ferment soybean meal in order to solve this problem.

Results

Bacteria were isolated from fermented soy foods and the grass carp intestine, and strains selected for high protease, cellulase and amylase activities. The isolated bacteria were characterized as Bacillus cereus, Bacillus subtilis and Bacilus amyloliquefacien, respectively. Fermentation with food-derived Isolate-2 and fish-derived F-9 increased crude protein content by 5.32% and 8.27%, respectively; improved the amino acid profile by increasing certain essential amino acids, broke down larger soy protein to 35 kDa and under, eliminated antigenicity against glycinin and β-conglycinin, and removed raffinose and stachyose in the soybean meal following a 24-h fermentation.

Conclusions

Our results suggest these two B. amyloliquefaciens bacteria can efficiently solid state ferment soybean meal and ultimately produce a more utilizable food source for growing healthy piglets.

Biodegradation of food waste using microbial cultures producing thermostable α-amylase and cellulase under different pH and temperature

The aim of this work was to study the biodegradation of food waste employing thermostable α-amylase and cellulase enzymes producing bacteria. Four potential isolates were identified which were capable of producing maximum amylase and cellulase and belong to the amylolytic strains, Brevibacillus borstelensis and Bacillus licheniformis; cellulolytic strains, Bacillus thuringiensis and Bacillus licheniformis, respectively. These strains were selected based on its higher cell density, enzymatic activities and stability at a wide range of pH and temperature compared to other strains. The results indicated that 1:1 ratio of pre and post consumed food wastes (FWs) were helpful to facilitate the degradation employing bacterial consortium. In addition, organic matter decomposition and chemical parameters of the end product quality also indicated that bacterial consortium was very effective for 1:1 ratio of FWs degradation as compared to the other treatments.

Bacillus subtilis with endocellulase and exocellulase activities isolated in the thermophilic phase from composting with coffee residues

The goal of this study was to isolate, select and characterize bacteria with cellulolytic activity from two different coffee residue composting piles, one of which had an internal temperature of 57°C and pH 5.5 and the other, a temperature of 61°C, and pH 9.3. Culture media were manipulated with carboxymethylcellulose and crystalline cellulose as sole carbon sources. The enzyme activity was assessed by hydrolysis halo formation, reducing sugar production and zymograms. Three out of twenty isolated strains showed higher enzymatic activity and were identified as Bacillus subtilis according to their morphological, physiological, biochemical characteristics and based on the sequence analysis of 16S rDNA regions. The enzymatic extracts of the three selected strains showed exocellulase and endocellulase maximum activity of 0.254 and 0.519 U/ml, respectively; the activity of these enzymes was maintained even in acid pH (4.8) and basic (9.3) and at temperatures of up to 60°C. The enzymatic activities observed in this study are within the highest reported for cellulose produced by bacteria of the genus Bacillus. Endocellulase activity was shown in the zymograms from 24h until 144h of incubation. Furthermore, the pH effect on the endocellulase activity is reported for the first time by zymograms. The findings in this study entail the possibility to use these enzymes in the procurement of fermentable substrates for the production of energy from the large amount of residues generated by the coffee agroindustry.

Evaluation of gastrointestinal bacterial population for the production of holocellulose enzymes for biomass deconstruction

The gastrointestinal (GI) habitat of ruminant and non-ruminant animals sustains a vast ensemble of microbes that are capable of utilizing lignocellulosic plant biomass. In this study, an indigenous swine (Zovawk) and a domesticated goat (Black Bengal) were investigated to isolate bacteria having plant biomass degrading enzymes. After screening and enzymatic quantification of eighty-one obtained bacterial isolates, Serratia rubidaea strain DBT4 and Aneurinibacillus aneurinilyticus strain DBT87 were revealed as the most potent strains, showing both cellulase and xylanase production. A biomass utilization study showed that submerged fermentation (SmF) of D2 (alkaline pretreated pulpy biomass) using strain DBT4 resulted in the most efficient biomass deconstruction with maximum xylanase (11.98 U/mL) and FPase (0.5 U/mL) activities (55°C, pH 8). The present study demonstrated that bacterial strains residing in the gastrointestinal region of non-ruminant swine are a promising source for lignocellulose degrading microorganisms that could be used for biomass conversion.

A novel enzyme-assisted approach for efficient extraction of Z-ligustilide from Angelica sinensis plants

Endophytes coexist with plants, in part, due to cellulase that allow saccharification of plant cell walls. The cellulase enzymes found in naturally occurring endophytes may exhibit stronger activity and more specificity than commercially available cellulase for enzyme-assisted extraction of compounds from medicinal plant materials. In order to identify endophytes with high cellulase activity, we screened endophytes taken from different parts of Angelica sinensis using the Congo red staining method. We identified three strains with higher cellulase activity. Of the 3 strains identified, No.Lut1201 increased the yield of extracted Z-ligustilide 2 fold compared to commercially available cellulase (Ningxia Sunson) using a cellulase-assisted extraction method and traditional extraction methods. Scanning electron microscopy clearly demonstrated that the cellulase extracted from endophytes enhance cell wall polysaccharide degradation as well as Z-ligustilide extraction from Radix Angelica sinensis (RAS). The current study provides a new method and ideas of using cellulase of endophytes for improving the extraction of compounds from medicinal plants.

Production of a recombinant swollenin from Trichoderma harzianum in Escherichia coli and its potential synergistic role in biomass degradation

Background

Fungal swollenins (SWOs) constitute a class of accessory proteins that are homologous to canonical plant expansins. Expansins and expansin-related proteins are well known for acting in the deagglomeration of cellulose structure by loosening macrofibrils. Consequently, SWOs can increase the accessibility and efficiency of the other enzymes involved in the saccharification of cellulosic substrates. Thus, SWOs are promising targets for improving the hydrolysis of plant biomass and for use as an additive to enhance the efficiency of an enzyme cocktail designed for the production of biofuels.

Results

Here, we report the initial characterization of an SWO from Trichoderma harzianum (ThSwo) that was successfully produced using Escherichia coli as a host. Initially, transcriptome and secretome data were used to compare swo gene expression and the amount of secreted ThSwo. The results from structural modeling and phylogenetic analysis of the ThSwo protein showed that ThSwo does preserve some structural features of the plant expansins and family-45 glycosyl hydrolase enzymes, but it evolutionarily diverges from both of these protein classes. Recombinant ThSwo was purified at a high yield and with high purity and showed secondary folding similar to that of a native fungal SWO. Bioactivity assays revealed that the purified recombinant ThSwo created a rough and amorphous surface on Avicel and displayed a high synergistic effect with a commercial xylanase from T. viride, enhancing its hydrolytic performance up to 147 ± 7%.

Conclusions

Many aspects of the structure and mechanism of action of fungal SWOs remain unknown. In the present study, we produced a recombinant, active SWO from T. harzianum using a prokaryotic host and confirmed its potential synergistic role in biomass degradation. Our work paves the way for further studies evaluating the structure and function of this protein, especially regarding its use in biotechnology.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0697-6) contains supplementary material, which is available to authorized users.

Insight into Enzymatic Degradation of Corn, Wheat, and Soybean Cell Wall Cellulose Using Quantitative Secretome Analysis of Aspergillus fumigatus

Lignocelluloses contained in animal forage cannot be digested by pigs or poultry with 100% efficiency. On contrary, Aspergillus fumigatus, a saprophytic filamentous fungus, is known to harbor 263 glycoside hydrolase encoding genes, suggesting that A. fumigatus is an efficient lignocellulose degrader. Hence the present study uses corn, wheat, or soybean as a sole carbon source to culture A. fumigatus under animal physiological condition to understand how cellulolytic enzymes work together to achieve an efficient degradation of lignocellulose. Our results showed that A. fumigatus produced different sets of enzymes to degrade lignocelluloses derived from corn, wheat, or soybean cell wall. In addition, the cellulolytic enzymes produced by A. fumigatus were stable under acidic condition or at higher temperatures. Using isobaric tags for a relative and absolute quantification (iTRAQ) approach, a total of ∼600 extracellular proteins were identified and quantified, in which ∼50 proteins were involved in lignocellulolysis, including cellulases, hemicellulases, lignin-degrading enzymes, and some hypothetical proteins. Data are available via ProteomeXchange with identifier PXD004670. On the basis of quantitative iTRAQ results, 14 genes were selected for further confirmation by RT-PCR. Taken together, our results indicated that the expression and regulation of lignocellulolytic proteins in the secretome of A. fumigatus were dependent on both nature and complexity of cellulose, thus suggesting that a different enzyme system is required for degradation of different lignocelluloses derived from plant cells. Although A. fumigatus is a pathogenic fungus and cannot be directly used as an enzyme source, as an efficient lignocellulose degrader its strategy to synergistically degrade various lignocelluloses with different enzymes can be used to design enzyme combination for optimal digestion and absorption of corn, wheat, or soybean that are used as forage of pig and poultry.

Bifunctional recombinant cellulase-xylanase (rBhcell-xyl) from the polyextremophilic bacterium Bacillus halodurans TSLV1 and its utility in valorization of renewable agro-residues

The thermostable bifunctional CMCase and xylanase encoding gene (rBhcell-xyl) from Bacillus halodurans TSLV1 has been expressed in Escherichia coli. The recombinant E. coli produced rBhcell-xyl (CMCase 2272 and 910 U L^-1 xylanase). The rBhcell-xyl is a ~62-kDa monomeric protein with temperature and pH optima of 60 °C and 6.0 with T_1/2 of 7.0 and 3.5 h at 80 °C for CMCase and xylanase, respectively. The apparent K _m values (CMC and Birchwood xylan) are 3.8 and 3.2 mg mL^-1. The catalytic efficiency (k _cat/K _m ) values of xylanase and CMCase are 657 and 171 mL mg^-1 min^-1, respectively. End-product analysis confirmed that rBhcell-xyl is a unique endo-acting enzyme with exoglucanase activity. The rBhcell-xyl is a GH5 family enzyme possessing single catalytic module and carbohydrate binding module. The action of rBhcell-xyl on corn cobs and wheat bran liberated reducing sugars, which can be fermented to bioethanol and fine biochemicals.

Cellulolytic Activity of Thermophilic Bacilli Isolated from Tattapani Hot Spring Sediment in North West Himalayas

Eight thermophilic bacterial strains were isolated from Tattapani Hot spring and screened for various hydrolytic enzymes including cellulases. The isolated bacterial strains were identified as Geobacillus thermodenitrificans IP_WH1(KP842609), Bacillus licheniformis IP_WH2(KP842610), B. aerius IP_WH3(KP842611), B. licheniformis IP_WH4(KP842612), B. licheniformis IP_60Y(KP842613), G. thermodenitrificans IP_60A1(KP842614), Geobacillus sp. IP_60A2(KP842615) and Geobacillus sp. IP_80TP(KP842616) after 16S ribotying. Out of the eight isolates Geobacillus sp. IP_80TP grew best at 80 °C whereas rest of the isolates showed optimal growth at 60 °C. G. thermodenitrificans IP_WH1 produced a thermotolerant cellulase with maximum activity at 60 °C.

Solid-substrate bioprocessing of cow dung for the production of carboxymethyl cellulase by Bacillus halodurans IND18

The production of carboxymethyl cellulase (CMCase) by Bacillus halodurans IND18 under solid substrate fermentation (SSF) using cow dung was optimized through two level full factorial design and second order response surface methodology (RSM). The central composite design (CCD) was employed to optimize the vital fermentation parameters, such as pH of the substrate, concentration of nitrogen source (peptone) and ion (sodium dihydrogen phosphate) sources in medium for achieving higher enzyme production. The optimum medium composition was found to be 1.46% (w/w) peptone, 0.095% (w/w) sodium dihydrogen phosphate and pH 8.0. The model prediction of 4210IU/g enzyme activity at optimum conditions was verified experimentally as 4140IU/g. The enzyme was active over a broad temperature range (40-60±1°C) and pH (7.0-9.0) with maximal activity at 60±1°C and pH 8.0. This study demonstrated the potential of cow dung as novel substrate for CMCase production.