No abstract

Geobacillus thermoglucosidasius is a thermophilic bacterium that is able to ferment both C6 and C5 sugars to produce ethanol. During growth on hemicellulose biomass, an intracellular β-xylosidase catalyses the hydrolysis of xylo-oligosaccharides to the monosaccharide xylose, which can then enter the pathways of central metabolism. The gene encoding a G. thermoglucosidasius β-xylosidase belonging to CAZy glycoside hydrolase family GH52 has been cloned and expressed in Escherichia coli. The recombinant enzyme has been characterized and a high-resolution (1.7 Å) crystal structure has been determined, resulting in the first reported structure of a GH52 family member. A lower resolution (2.6 Å) structure of the enzyme-substrate complex shows the positioning of the xylobiose substrate to be consistent with the proposed retaining mechanism of the family; additionally, the deep cleft of the active-site pocket, plus the proximity of the neighbouring subunit, afford an explanation for the lack of catalytic activity towards the polymer xylan. Whilst the fold of the G. thermoglucosidasius β-xylosidase is completely different from xylosidases in other CAZy families, the enzyme surprisingly shares structural similarities with other glycoside hydrolases, despite having no more than 13% sequence identity.

No abstract

Antarctica is covered by multiple larger glaciers with diverse extreme conditions. Microorganisms in Antarctic regions are primarily responsible for diverse biogeochemical processes. The identity and functionality of microorganisms from polar glaciers are defined. However, little is known about microbial communities from the high elevation glaciers. The Union Glacier, located in the inland of West Antarctica at 79°S, is a challenging environment for life to survive due to the high irradiance and low temperatures. Here, soil and rock samples were obtained from three high mountains (Rossman Cove, Charles Peak, and Elephant Head) adjacent to the Union Glacier. Using metagenomic analyses, the functional microbial ecosystem was analyzed through the reconstruction of carbon, nitrogen and sulfur metabolic pathways. A low biomass but diverse microbial community was found. Although archaea were detected, bacteria were dominant. Taxa responsible for carbon fixation were comprised of photoautotrophs (Cyanobacteria) and chemoautotrophs (mainly Alphaproteobacterial clades: Bradyrhizobium, Sphingopyxis, and Nitrobacter). The main nitrogen fixation taxa were Halothece (Cyanobacteria), Methyloversatilis, and Leptothrix (Betaproteobacteria). Diverse sulfide-oxidizing and sulfate-reducing bacteria, fermenters, denitrifying microbes, methanogens, and methane oxidizers were also found. Putative producers provide organic carbon and nitrogen for the growth of other heterotrophic microbes. In the biogeochemical pathways, assimilation and mineralization of organic compounds were the dominant processes. Besides, a range of metabolic pathways and genes related to high irradiance, low temperature and other stress adaptations were detected, which indicate that the microbial communities had adapted to and could survive in this harsh environment. These results provide a detailed perspective of the microbial functional ecology of the Union Glacier area and improve our understanding of linkages between microbial communities and biogeochemical cycling in high Antarctic ecosystems.

In a global context where the development of more environmentally conscious technologies is an urgent need, the demand for enzymes for industrial processes is on the rise. Compared to conventional chemical catalysts, the implementation of biocatalysis presents important benefits including higher selectivity, increased sustainability, reduction in operating costs and low toxicity, which translate into cleaner production processes, lower environmental impact as well as increasing the safety of the operating staff. Most of the currently available commercial enzymes are of mesophilic origin, displaying optimal activity in narrow ranges of conditions, which limits their actual application under industrial settings. For this reason, enzymes from extremophilic microorganisms stand out for their specific characteristics, showing higher stability, activity and robustness than their mesophilic counterparts. Their unique structural adaptations allow them to resist denaturation at high temperatures and salinity, remain active at low temperatures, function at extremely acidic or alkaline pHs and high pressure, and participate in reactions in organic solvents and unconventional media. Because of the increased interest to replace chemical catalysts, the global enzymes market is continuously growing, with hydrolases being the most prominent type of enzymes, holding approximately two-third share, followed by oxidoreductases. The latter enzymes catalyze electron transfer reactions and are one of the most abundant classes of enzymes within cells. They hold a significant industrial potential, especially those from extremophiles, as their applications are multifold. In this article we aim to review the properties and potential applications of five different types of extremophilic oxidoreductases: laccases, hydrogenases, glutamate dehydrogenases (GDHs), catalases and superoxide dismutases (SODs). This selection is based on the extensive experience of our research group working with these particular enzymes, from the discovery up to the development of commercial products available for the research market.

A CNT electrode modified with a thermophilic laccase improved the shelf life and functional stability of the enzyme–CNT composite.

The exceptional potential for application that metallic nanoparticles (MeNPs) have shown, has steadily increased their demand in many different scientific and technological areas, including the biomedical and pharmaceutical industry, bioremediation, chemical synthesis, among others. To face the current challenge for transitioning toward more sustainable and ecological production methods, bacterial biosynthesis of MeNPs, especially from extremophilic microorganisms, emerges as a suitable alternative with intrinsic added benefits like improved stability and biocompatibility. Currently, biogenic nanoparticles of different relevant metals have been successfully achieved using different bacterial strains. However, information about biogenic nanoparticles from rare earth elements (REEs) is very scarce, in spite of their great importance and potential. This mini review discusses the current understanding of metallic nanoparticle biosynthesis by extremophilic bacteria, highlighting the relevance of searching for bacterial species that are able to biosynthesize RRE nanoparticles.

With the advent of the industrial revolution, the use of toxic compounds has grown exponentially, leading to a considerable pollution of the environment. Consequently, the development of more environmentally conscious technologies is an urgent need. Industrial biocatalysis appears as one potential solution, where a higher demand for more robust enzymes aims to replace toxic chemical catalysts. To date, most of the commercially available enzymes are of mesophilic origin, displaying optimal activity in narrow ranges of temperature and pH (i.e., between 20°C and 45°C, neutral pH), limiting their actual application under industrial reaction settings, where they usually underperform, requiring larger quantities to compensate loss of activity. In order to obtain novel biocatalysts better suited for industrial conditions, an efficient solution is to take advantage of nature by searching and discovering enzymes from extremophiles. These microorganisms and their macromolecules have already adapted to thrive in environments that present extreme physicochemical conditions. Hence, extremophilic enzymes stand out for showing higher activity, stability, and robustness than their mesophilic counterparts, being able to carry out reactions at nonstandard conditions. In this brief research report we describe three examples to illustrate a stepwise strategy for the development and production of commercial extremozymes, including a catalase from an Antarctic psychrotolerant microorganism, a laccase from a thermoalkaliphilic bacterium isolated from a hot spring and an amine-transaminase from a thermophilic bacterium isolated from a geothermal site in Antarctica. We will also explore some of their interesting biotechnological applications and comparisons with commercial enzymes.