Laccase mediated delignification of wasted and non-food agricultural biomass: Recent developments and challenges.

Utilization of microbial laccases is considered as the cleaner and target specific biocatalytic mechanism for the recovery of cellulose and hemicelluloses from nonfood and wasted agricultural, lignocellulosic biomass (LCB). The extent of lignin removal by laccase depends on the biochemical composition of biomass and the redox potential (E0) of the biocatalyst. Intensive research efforts are going on all over the world for the recognition of appropriate and easily available agricultural lignocellulosic feedstocks to exploit maximally for the production of value-added bioproducts and biofuels. In such circumstances, laccase can play a major role as a leading biocatalyst and potent substitute for chemical based deconstruction of the lignocellulosic materials. The limited commercialization of laccase at an industrial scale has been feasible due to its full working efficiency mostly expressed in the presence of cost intensive redox mediators only. Although, recently there are some reports that came on the mediator free biocatalysis of enzyme but still not considerably explored and neither understood in depth. The present review will address the various research gaps and shortcomings that acted as the big hurdles before the complete exploitation of laccases at an industrial scale. Further, this article also reveals insights on different microbial laccases and their diverse functional environmental conditions that affect the deconstruction process of LCB.

Engineering of Bacillus lipase by directed evolution for enhanced thermal stability: effect of isoleucine to threonine mutation at protein surface.

A lip gene from a Bacillus isolate was cloned and expressed in E. coli. By thermal denaturation analysis, T(1/2) of lipase was observed to be 7 min at 50°C with less than 10% activity after 1 h incubation at 50°C. To expand the functionality of cloned lipase, attempts have been made to create thermostable variants of lip gene. A lipase variant with an isoleucine to threonine amino acid substitution at the protein surface was isolated that demonstrated higher thermostability than its wild type predecessor. To explore the structure-function relationship, the lip gene product of wild type (WT) and mutant was characterized in detail. The mutation enhanced the specific activity of enzyme by 2-folds when compared with WT. The mutant enzyme showed enhanced T(1/2) of 21 min at 50°C. The kinetic parameters of the mutant enzyme were significantly altered. The mutant enzyme displayed higher affinity for substrate (decreased K ( m )) in comparison to the wild type. The k (cat) and catalytic efficiency (k (cat)/K ( m )) of mutant were also enhanced by two and five times, respectively, as compared with the WT. The mutation resides on the part of helix which is exposed to the solvent and away from the catalytic triad. The replacement of a solvent exposed hydrophobic residue (Ile) in WT with a hydrophilic residue (Thr) in mutant might impart thermostability to the protein structure.

Upfront Xpert MTB/RIF for diagnosis of pediatric TB-Does it work? Experience from India.

BACKGROUND: Diagnosis of TB in pediatric population poses several challenges. A novel initiative was implemented in several major cities of India aimed at providing upfront access to free-of-cost Xpert MTB/RIF to presumptive pediatric TB cases. This paper aims to describe the experience of implementing this large initiative and assess feasibility of the intervention in high TB burden settings. METHODS: Data were drawn from the pediatric TB project implemented in 10 major cities of India between April 2014 and March 2018. In each city, providers, both public and private, were engaged and linked with a high throughput Xpert MTB/RIF lab (established in that city) through rapid specimen transportation and electronic reporting system. Rates and proportions were estimated to describe the characteristics of this cohort. RESULTS: Of the total 94,415 presumptive pediatric TB cases tested in the project, 6,270 were diagnosed positive for MTB (6.6%) on Xpert MTB/RIF (vs 2% on smear microscopy). Among MTB positives, 545 cases were rifampicin resistant (8.7%). The median duration between collection of specimens and reporting of results was 0 days (same day) and >89% cases were initiated on treatment. Approximately 50% of the specimens tested were non-sputum. The number of providers/facilities engaged under the project increased >10-fold (from 124 in Q2'14 to 1416 in Q1'18). CONCLUSION: This project, which was one of the largest initiatives globally among pediatric population, demonstrated the feasibility of sustaining rapid and upfront access to free-of-cost Xpert MTB/RIF testing. The project underscores the efficiency of this rapid diagnostic assay in tackling several challenges in pediatric TB diagnosis, identifies opportunities for further interventions as well as brings to light scope for effective engagement with healthcare providers. The findings have facilitated a policy decision by National TB Programme mandating the use of Xpert MTB/RIF as a primary diagnostic tool for TB diagnosis in children, which is being scaled-up.

Frequency of mutations in rifampicin and isoniazid resistant isolates of M. tuberculosis: an analysis from Central India.

BACKGROUND: The spread of drug-resistant tuberculosis has challenged tuberculosis control strategies globally. The present study aims to analyze the frequency of mutations in rpoB, katG and inhA genes in strains of M. tuberculosis complex (MTBC) circulating in Central India. It is anticipated that the findings may provide a starting point to understand the evolutionary success of drug-resistant strains of MTBC in this region. METHODS: Line probe assay was carried out on 720 consecutive sputum samples of MDR suspects from June 2012 to May 2013. Mutation frequencies in the rpoB, katG and inhA genes were analyzed. RESULTS: Mutations were identified in 269 (37.6%) samples, as follows: 55 (7.6%) samples had mutations conferring resistance to only isoniazid, 84 (11.6%) had mutations conferring resistance to only rifampicin and 130 (18%) isolates had mutations conferring resistance to both isoniazid and rifampicin. The most frequent mutation in the rpoB gene was at codon S531L, seen in 141 (19.5%) isolates. The most frequent mutation in the katG gene was at codon S315T1, seen in 151 (20.9%) isolates; and in the inhA gene at codon C15T, seen in 21 (2.9%) isolates. Some unidentified mutations were also observed. CONCLUSION: The patterns and the frequency of the mutations identified in this study indicate the most frequent mutations at S531L codon in the rpoB gene, S315T1 codon in the katG gene and C15T codon in the promoter region of the inhA gene. Controlling the emergence and spread of MDR TB requires an understanding of the evolution of these mutations.

New Insight into Old Bacillus Lipase: Solvent Stable Mesophilic Lipase Demonstrating Enzyme Activity towards Cold.

BACKGROUND: Bacillus lipases are grouped in subfamily 1.4, which are the smallest known lipases having a molecular mass of 19.6 kDa. Lipases active in a wide range of temperatures, specifically at low temperatures, have an advantage under low water conditions for industrial application. METHODS: The lipase gene was cloned and expressed in Escherichia coli. The protein was purified and biochemically characterized in detail. RESULTS: A lipase gene was cloned from a mesophilic Bacillus isolate. Sequence analysis revealed an open reading frame of 633 bp in length. The predicted molecular mass of protein was 22.6 kDa. The purified enzyme displayed optimal activity at 35 °C and pH 8.0. Interestingly, this mesophilic enzyme was also cold active showing retention of 75 and 55% relative enzyme activity at 20 and 10 °C, respectively. The purified lipase was stable in various organic solvents (50% v/v) and ionic liquids (5% v/v). The enzyme displayed maximum activity with paranitrophenyl laurate (C12). kcat/Km values for the purified lipase were calculated to be 5.8 ± 0.6 × 10(-6). CONCLUSIONS: The lipase showed tolerance to various solvents as well as activity at low temperature. Therefore, this lipase might be of great potential to be employed in various industrial applications.

Intrinsically unstructured carboxy terminus of Bacillus lipase is essential for its function.

We have identified intrinsically unstructured C-terminus of a Bacillus lipase. In an effort to understand the possible role of this C-terminus unstructured region, 10, 20 and 30 amino acids were serially deleted from C-terminal region of the lipase. The catalytic properties of wild type and resulted truncated enzymes were compared. Deletion of 10 amino acids from C-terminus region resulted in decrease in transcription of lipase, specific enzyme activity and extracellular secretion of lipase in comparison to wild type while no effect on lipase aggregation was observed. Negligible activity was observed upon deletion of 20 amino acids. The homology model of the protein demonstrated that the tertiary structure of the protein was held together by these C-terminus residues due to six critically placed hydrogen bonds. Therefore C terminus was essential for the tertiary structure and enzyme activity of lipase. Due to structural flexibility and plasticity originating from the lack of a definite-ordered 3D structure, such disordered regions might represent a major functional advantage for proteins.

A thermostable lipolytic enzyme from a thermophilic Bacillus sp.: purification and characterization.

A thermophilic Bacillus sp. was isolated that secreted an extracellular, thermostable lipolytic enzyme. The enzyme was purified to 58 folds with a specific activity of 9730 units/mg of protein and yield of 10% activity by ammonium sulphate precipitation, Phenyl Sepharose chromatography, gel-permeation followed by Q Sepharose chromatography. The relative molecular mass of the protein was determined to be 61 kDa by SDS-PAGE and approximately 60 kDa by gel permeation chromatography. The enzyme showed optimal activity at 60-65 ( composite function)C and retained 100% activity after incubation at 60 ( composite function)C and pH 8.0 for 1 h. The optimum pH was determined to be 8.5. It exhibited 50% of its original activity after 65 min incubation at 70 ( composite function)C and 23 min incubation at 80 ( composite function)C. Catalytic function of lipase was activated by Mg(++) (10 mM), while mercury (10 mM) inactivated the enzyme completely. No effect on enzyme activity was observed with trypsin and chymotrypsin treatment, while 50% inhibition was observed with thermolysin. It was demonstrated that PMSF, SDS, DTT, EDTA, DEPC, betaME (100 mM each) and eserine (10 mM) inhibited the activity of the lipolytic enzyme. With p-nitrophenyl laurate as a substrate, the enzyme exhibited a K ( m ) and V (max) of 0.5 mM and 0.139 microM/min/ml. The enzyme showed preference for short chain triacylglycerol and hydrolyzes triolein at all positions. In contrast to other thermostable Bacillus lipases, this enzyme has very low content of hydrophobic amino acids (22.58 %). Immunological studies showed that the active site and antigen-binding site of enzyme do not overlap.