Lipases in Green Chemistry: Deep Eutectic Solvents (DES) as New Green Solvents.

Deep eutectic solvents (DES) may become important alternatives as versatile, biodegradable, and cost-effective solvents for biocatalysis. Especially for reactions where substrates and products of different polarities are combined, the design of a tailored solvent that may dissolve all compounds-while being enzyme-compatible at the same time-appears to be a strong ally in sustainable chemistry. Herein it is shown that the combination of DES with "water as cosolvent" (in a range from 5% to 20% water, v/v) leads to non-conventional solvents with significantly reduced viscosity. In these media, lipases and proteases can perform synthetic reactions efficiently, and hydrolytic side reactions remain suppressed (even at 20% water, v/v). The use of these less viscous non-conventional media could also provide options for hydrolase-catalyzed synthetic reactions even in continuous fashion.

From gene to biorefinery: microbial ß-etherases as promising biocatalysts for lignin valorization.

The set-up of biorefineries for the valorization of lignocellulosic biomass will be core in the future to reach sustainability targets. In this area, biomass-degrading enzymes are attracting significant research interest for their potential in the production of chemicals and biofuels from renewable feedstock. Glutathione-dependent ß-etherases are emerging enzymes for the biocatalytic depolymerization of lignin, a heterogeneous aromatic polymer abundant in nature. They selectively catalyze the reductive cleavage of ß-O-4 aryl-ether bonds which account for 45-60% of linkages present in lignin. Hence, application of ß-etherases in lignin depolymerization would enable a specific lignin breakdown, selectively yielding (valuable) low-molecular-mass aromatics. Albeit ß-etherases have been biochemically known for decades, only very recently novel ß-etherases have been identified and thoroughly characterized for lignin valorization, expanding the enzyme toolbox for efficient ß-O-4 aryl-ether bond cleavage. Given their emerging importance and potential, this mini-review discusses recent developments in the field of ß-etherase biocatalysis covering all aspects from enzyme identification to biocatalytic applications with real lignin samples.

Enzymatic hydrolysis of microcrystalline cellulose in concentrated seawater.

This communication explores the use of seawater (1X) and concentrated seawater (2X and 4X) as reaction media for the enzyme-catalyzed depolymerization of cellulose. The commercially available Accellerase-1500® - a "cocktail" of different glycosidases - is able to depolymerize several amorphous celluloses and microcrystalline cellulose Avicel® in these reaction media, at slightly lower rates (ca. 90%) than those observed when reactions are performed in pure citrate buffer (control reactions). Remarkably, at concentrated seawater effluents enzymes also display significant rates of cellulose hydrolysis. Considering the expected increasing shortages in accessibility to fresh drinkable water, the herein-reported concept may provide novel inspiring leads for a smart use of resources in an environmentally-friendly and efficient manner, and for the genetic development of cellulases highly active and stable in concentrated seawater solutions.

Asymmetric reduction of ketones with recombinant E. coli whole cells in neat substrates.

The asymmetric reduction of ketones is performed by using lyophilized whole cells in neat substrates with defined water activity (a(w)). Ketones and alcohols prone to be unstable in aqueous media can now be converted via biocatalysis.

Recent trends in industrial microbiology.

The majority of current biotechnological applications are of microbial origin, and it is widely appreciated that the microbial world contains by far the greatest fraction of biodiversity in the biosphere. Because of their biotech impact, numerous efforts are being undertaken worldwide, with an ultimate goal to deliver new usable substances of microbial origin to the marketplace. However, the direct isolation of microbes always revealed that the majority are not amenable to be cultured and no representatives for many major microbial phyla have been thus far characterized. Therefore, the knowledge on new microbes and/or genomic information thereof, or from their communities, will pose an enormous potential to provide industry with novel products and processes based on the use of microbial resources, and contribute to and extend the basic mechanistic knowledge on the functioning of organisms. The present review highlights some examples and advances in the exploration of the genetic reservoir of (un)cultured microbes for industrial applications.

Rational strategy for the production of new crude lipases from Candida rugosa.

Candida rugosa was cultured using different inducers (oleic acid, olive oil, sunflower oil, n-dodecanol and glycerol) as the only carbon source in batch conditions, as well as in several fed-batch fermentations (oleic acid as inducer) at variable feed rate conditions. The N-terminal analysis of each crude lipase revealed that, while the isoenzymes Lip2 and Lip3 are always secreted (at different proportions depending on the inducer), Lip1 was produced only using n-dodecanol (batch conditions) or oleic acid (fed-batch at high feed rate). The nature of the inducer controls the isoenzyme percentage; when this is fixed, as well as the feed rate in fed-batch fermentation, the isoenzymatic profile remained unaltered and the samples differed only in the activity of the lipases, as determined by heptyl oleate synthesis.