Biochemical and molecular characterization of thermo-alkali tolerant xylanase producing bacteria from thermal springs of Manikaran

A comprehensive review on microbial production of 1,2-propanediol: micro-organisms, metabolic pathways, and metabolic engineering

1,2-Propanediol is an important building block as a component used in the manufacture of unsaturated polyester resin, antifreeze, biofuel, nonionic detergent, etc. Commercial production of 1,2-propanediol through microbial biosynthesis is limited by low efficiency, and chemical production of 1,2-propanediol requires petrochemically derived routes involving wasteful power consumption and high pollution emissions. With the development of various strategies based on metabolic engineering, a series of obstacles are expected to be overcome. This review provides an extensive overview of the progress in the microbial production of 1,2-propanediol, particularly the different micro-organisms used for 1,2-propanediol biosynthesis and microbial production pathways. In addition, outstanding challenges associated with microbial biosynthesis and feasible metabolic engineering strategies, as well as perspectives on the future microbial production of 1,2-propanediol, are discussed.

The plasma metabolome of Atlantic salmon as studied by 1H NMR spectroscopy using standard operating procedures: effect of aquaculture location and growth stage

INTRODUCTION

Metabolomics applications to the aquaculture research are increasing steadily. The use of standardized proton nuclear magnetic resonance (¹H NMR) spectroscopy can provide the aquaculture industry with an unbiased, reproducible, and high-throughput screening tool, which can help to diagnose nutritional and disease-related metabolic disorders in farmed fish.

OBJECTIVE

Standard operating procedures developed for analysing (human) plasma by ¹H NMR were applied to fingerprint the metabolome in plasma samples collected from Atlantic salmon. The aim was to explore the metabolome of salmon plasma in relation to growth stage and sampling site.

METHODS

A total of 72 salmon were collected from three aquaculture sites in Norway (Lat. 65, 67, and 70 °N) and over two sampling events (December 2017 and November 2018). Plasma drawn from each salmon was measured by ¹H NMR and metabolites were quantified using the SigMa software. The NMR data was analysed by principal component analysis (PCA) and ANOVA-simultaneous component analysis (ASCA).

RESULTS

Important metabolic differences were evidenced, with adult salmon having a much higher content of very low-density lipoproteins and cholesterol in their plasma, while smolts displayed significantly higher levels of propylene glycol. Overall, 24% of the metabolite variation was due to the growth stage, whereas 12% of the metabolite variation was related to the aquaculture site and practice (p < 0.001).

CONCLUSION

This study provides a baseline investigation of the plasma metabolome of the Atlantic salmon and demonstrates how ¹H NMR metabolomics can be used in future investigations for comparing aquaculture practices and their influence on the fish metabolome.

Diversity and enzymatic potential of thermophilic bacteria associated with terrestrial hot springs in Algeria

This study aims to determine the diversity of culturable thermophilic bacteria isolated from eight terrestrial hot springs in Northeastern of Algeria using the conventional methods, SDS-PAGE fingerprinting of whole-cell proteins and 16S rRNA gene sequencing. In addition, their hydrolytic enzyme activities were also investigated. A total of 293 strains were isolated from the hot springs' water and sediment using different culture media. Overall, five distinct bacterial groups were characterized by whole-cell protein pattern analysis. Based on the 16S rRNA gene sequencing of 100 selected strains, the isolates were assigned to the following three major phyla: Firmicutes (93%), Deinococcus-Thermus (5%), and Actinobacteria (2%), which included 27 distinct species belonging to 12 different phylotypes, Aeribacillus, Aneurinibacillus, Anoxybacillus, Bacillus, Brevibacillus, Geobacillus, Laceyella, Meiothermus, Saccharomonospora, Thermoactinomyces, Thermobifida, and Thermus. The screening for nine extracellular enzymes showed that 65.87% of the isolates presented at least five types of enzyme activities, and 6.48% of strains combined all tested enzymes (amylase, cellulase, pectinase, esculinase, protease, gelatinase, lipase, lecithinase, and nuclease). It was found that Bacillus, Anoxybacillus, Aeribacillus, and Aneurinibacillus were the genera showing the highest activities. Likewise, the study showed an abundant and diverse thermophilic community with novel taxa presenting a promising source of thermozymes with important biotechnological applications. This study showed that a combined identification method using SDS-PAGE profiles of whole-cell proteins and subsequent 16S rRNA gene sequence analysis could successfully differentiate thermophilic bacteria from Algerian hot springs.

Thermostable Xanthine Oxidase Activity from Bacillus pumilus RL-2d Isolated from Manikaran Thermal Spring: Production and Characterization

Xanthine oxidase is an important enzyme of purine metabolism that catalyzes the hydroxylation of hypoxanthine to xanthine and then xanthine to uric acid. A thermostable xanthine oxidase is being reported from a thermophilic organism RL-2d isolated from the Manikaran (Kullu) hot spring of Himachal Pradesh (India). Based on the morphology, physiological tests, and 16S rDNA gene sequence, RL-2d was identified as Bacillus pumilus. Optimization of physiochemical parameters resulted into 4.1-fold increase in the xanthine oxidase activity from 0.051 U/mg dcw (dry cell weight) to 0.209 U/mg dcw. The xanthine oxidase of B. pumilus RL-2d has exhibited very good thermostability and its t1/2 at 70 and 80 °C were 5 and 1 h, respectively. Activity of this enzyme was strongly inhibited by Hg(2+), Ag(+) and allopurinol. The investigation showed that B. pumilus RL-2d exhibited highest xanthine oxidase activity and remarkable thermostability among the other xanthine oxidases reported so far.

Thermophilic bacteria in Moroccan hot springs, salt marshes and desert soils

The diversity of thermophilic bacteria was investigated in four hot springs, three salt marshes and 12 desert sites in Morocco. Two hundred and forty (240) thermophilic bacteria were recovered, identified and characterized. All isolates were Gram positive, rod-shaped, spore forming and halotolerant. Based on BOXA1R-PCR and 16S rRNA gene sequencing, the recovered isolates were dominated by the genus Bacillus (97.5%) represented by B. licheniformis (119), B. aerius (44), B. sonorensis (33), B. subtilis (subsp. spizizenii (2) and subsp. inaquosurum (6)), B. amyloliquefaciens (subsp. amyloliquefaciens (4) and subsp. plantarum (4)), B. tequilensis (3), B. pumilus (3) and Bacillus sp. (19). Only six isolates (2.5%) belonged to the genus Aeribacillus represented by A. pallidus (4) and Aeribacillus sp. (2). In this study, B. aerius and B. tequilensis are described for the first time as thermophilic bacteria. Moreover, 71.25%, 50.41% and 5.41% of total strains exhibited high amylolytic, proteolytic or cellulolytic activity respectively.