Natural biodiversity undoubtedly inspires biocatalysis research and innovation.Biotransformations of interest also inspire the search for appropriate biocatalysts in nature.Indeed, natural genetic resources have been found to support the hydrolysis and synthesis of not only common but also unusual synthetic scaffolds. The emerging tool of metagenomics has the advantage of allowing straightforward identification of activity directly applicable as biocatalysis. However, new enzymes must not only have outstanding properties in terms of performance but also other properties superior to those of well-established commercial preparations in order to successfully replace the latter. Esterases (EST) and lipases (LIP) from the α/ -hydrolase fold superfamily are among the enzymes primarily used in biocatalysis. Accordingly, they have been extensively examined with metagenomics. Here we provided an updated (October 2015) overview of sequence and functional datasets of 288 EST-LIP enzymes with validated functions that have been isolated in metagenomes and (mostly partially) characterized. Through sequence, biochemical and reactivity analyses we attempted to understand the phenomenon of variability and versatility within this group of enzymes and to implement this knowledge to identify sequences encoding EST-LIP which may be useful for biocatalysis. We found that the diversity of described EST-LIP polypeptides was not dominated by a particular type of protein or highly similar clusters of proteins but rather by diverse nonredundant sequences. Purified EST-LIP exhibited a wide temperature activity range of 10-85°C, although a preferred bias for a mesophilic temperature range (35-40ºC) was observed. At least 60% of the total characterized metagenomics-derived EST-LIP showed outstanding properties in terms of stability (solvent tolerance) and reactivity (selectivity and substrate profile), which are the features of interest in biocatalysis. We hope that, in the future, the search for and utilization of sequences similar to those already encoded and characterized EST-LIP enzymes 3 from metagenomes may be of interest for promoting unresolved biotransformations in the chemical industry. Some examples are discussed in this review.4
The disinfectant properties of chlorine have been known for centuries but in the last few years water chlorination has attracted some criticism due to its secondary effects and the increased resistance of bacterial strains to chlorine inactivation. In this paper the kinetics of inactivation by chlorine of different Gram‐positive and Gram‐negative bacterial strains isolated from chlorinated water is studied. The Gram‐positive strains were more resistant to chlorine and the behaviour of some of them in the presence of chloramphenicol suggests either the synthesis of unique proteins or aggregation of the bacteria as mechanisms of resistance to inactivation. The concept of Ki, the inactivation rate constant, by comparison with Ks in Michaelis‐Menten enzyme kinetics (considering enzymic saturation), or with Ks in Monod growth kinetics (considering limiting rates of transport and metabolism of substrates), may be an interesting parameter to define microbial resistance to disinfectants and toxics.
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