Characterization Studies of Natural Cellulosic Fibers Extracted from Shwetark Stem

The present investigation is mainly aimed to characterize the cellulosic fibers extracted from the stem of Shwetark plant to test its possibility to be used as polymeric reinforcement. Chemical analysis conducted on the Shwetark fibers shows the presence of cellulose (69.65 wt. %), lignin (16.82 wt. %), wax (0.53 wt. %), ash (3.4 wt. %) and wetness content (8.8 wt. %). The density of the fibers is found as 1.364 g/cm3. Crystallinity index and the crystallite size of the fibers are calculated as 72.06% and 3nm, respectively, from X-ray diffraction analysis while the presence of functional groups is ascertained from Fourier transform infrared analysis. Thermogravimetric analysis shows that the fibers are thermally stable till 225°C, and the fiber morphology seen through scanning electron microscopic shows that the fibers are composed of densely and uniformly packed cellulose microfibrils. Atomic force microscopic studies exemplify that Shwetark fibers can be used for tribological applications. The mean tensile strength and percentage elongation of the Shwetark fibers are found as 309.68 MPa and 1.092%, respectively. Thus, the studies show the possibility of Shwetark fibers as prospective candidates to replace harmful synthetic man-made fibers

Adequacy of examining one sputum specimen in tuberculosis drug resistance surveys

Objective/background: Collection of one spot and one morning sputum specimen is recommended for tuberculosis (TB) drug resistance surveys. This was a retrospective analysis of Mycobacterium tuberculosis cultures isolated from two spot sputum specimens collected from smear positive TB patients in a TB drug resistance survey. It was conducted to understand the value of a second specimen. Methods: A TB drug resistance survey was conducted in the state of Tamil Nadu, India, to estimate the prevalence of drug resistance among new sputum smear-positive (NSP) and previously treated (PT) patients diagnosed in Revised National Tuberculosis Control Program microscopy centers. A total of 2425 patients (1524 NSP and 901 PT cases) were enrolled in the study. From these patients, two spot sputum specimens (C and D) were collected within a period of 2 h. No preservative was added to sputum. The samples were transported at ambient conditions without cold storage to the central laboratory for culture of M. tuberculosis. Culture yield from each sample was computed and analyzed. Results: The proportion of cultures retrieved from C and D specimens among NSP cases (89.3% and 89.7%) and PT cases (90.8% and 90.3%) were similar. The culture grades of C and D samples were comparable (chi-square test, 3560.135; p<.001) and the agreement was moderate (kappa test, 0.454). Conclusion: The findings of the study reveal the adequacy of single spot sputum specimen from smear positive pulmonary TB patients for bacteriological examination in a quality-assured TB laboratory to determine precisely the level of drug resistance in a province of India

A genome-centric metagenomics approach to explain microbial community structure in anaerobic digesters

A functioning anaerobic digestion (AD) microbiome is integral for sludge management to be successful. Comprehensive ecological insights, and a full accounting of important microbial species, can help to improve and validate operational strategies. We analysed a time-series of metagenome samples obtained from full-scale anaerobic digesters and performed genome-resolved analysis to gain insight into the microbial community structure and potential functions of the AD microbiome. Ninety samples from three full-scale digesters were collected over a period of nine months and their nucleic acids extracted and subjected to shotgun sequencing (Illumina HiSeq2500; average 70M PE reads/sample). The raw reads were quality controlled, trimmed, assembled, binned, and dereplicated to obtain metagenome-assembled genomes (MAGs). Genome quality was assessed using the MIMAG criteria. The taxonomic assignment of the recovered MAGs was conducted using GTDB-Tk, and gene-level functional annotations were obtained using the KEGG, and CAZy databases. From ninety metagenome assemblies, 14,236 MAGs were recovered, of which 37%, 16%, and 1% satisfied medium-quality (Completeness > 50% and contamination 90% and contamination 90% and contamination <5% and presence of rRNA and tRNA genes), respectively. Taxonomical classification of the MAGs with at least medium quality (n =7666) revealed that 12.9%, 37.4%, and 77.1% of them belong to a novel family, genus, and species, respectively. A co-occurrence network analysis of the community structures in three replicate digesters revealed a highly interconnected network of microorganisms, suggesting the presence of a backbone in a functional AD microbial community. Functional analysis of the recovered MAGs showed the presence of three methanogenesis pathway modules, namely, methanogenesis via CO2, acetate, and trimethylamine. In addition, a specialization was observed in the hydrolytic bacterial community using CAZy annotation. In conclusion, we have obtained a catalogue of 166 MIMAG high-quality MAGs from a time-series metagenome survey of three full-scale anaerobic digesters situated in a tropical wastewater treatment plant, leading to novel ecological insights into the AD microbial community.Ministry of Education (MOE)National Research Foundation (NRF)Submitted/Accepted versionThis research was supported by the Singapore National Research Foundation (NRF) and the Ministry of Education under the Research Centre of Excellence Programme. Soheil A. Neshat acknowledges receipt of a Singapore International Graduate Award (SINGA)

Intracellular cellobiose metabolism and its applications in lignocellulose-based biorefineries

Complete hydrolysis of cellulose has been a key characteristic of biomass technology because of the limitation of industrial production hosts to use cellodextrin, the partial hydrolysis product of cellulose. Cellobiose, a ??-1,4-linked glucose dimer, is a major cellodextrin of the enzymatic hydrolysis (via endoglucanase and exoglucanase) of cellulose. Conversion of cellobiose to glucose is executed by ??-glucosidase. The complete extracellular hydrolysis of celluloses has several critical barriers in biomass technology. An alternative bioengineering strategy to make the bioprocessing less challenging is to engineer microbes with the abilities to hydrolyze and assimilate the cellulosic-hydrolysate cellodextrin. Microorganisms engineered to metabolize cellobiose rather than the monomeric glucose can provide several advantages for lignocellulose-based biorefineries. This review describes the recent advances and challenges in engineering efficient intracellular cellobiose metabolism in industrial hosts. This review also describes the limitations of and future prospectives in engineering intracellular cellobiose metabolism