Potential biocatalysts originating from sea environments

Abstract

This review is intended to give an account of the knowledge about known enzymes of marine origin described in literature thus stimulating future applications in biocatalysis that these biocatalysts can offer to a large spectra of end-users. The uniqueness of marine biocatalysts is not only based on habitat-related properties such as salt tolerance, hyperthermostability, barophilicity, cold adaptivity, etc. A marine enzyme in fact may carry more, e.g. novel chemical and stereochemical properties. This “chemical biodiversity” increases interest in this field; substrate specificity and affinity are evolved properties linked to the metabolic functions of the enzymes and to ecological asset related to the natural source and this is an important aspect in the bioprospecting for new biocatalysts. The importance of all examples reported should be sufficient to trigger the attention of the biocatalytically oriented scientific community towards marine environment as source of biocatalysts, and this could in turn enhance both new discovery and improvement of marine enzymes.

Introduction

Many excellent summarizing reports dealing with the topic of the biocatalysis have been disseminated during last decade in scientific literature. Any simple search for this kind of articles can give an exhaustive and detailed account of historical developments in the field, an aspect which is not included within this introductory part of the present review for the sake of space.

Generally speaking some specific topics in biocatalysis acquired great renown through the years, often due to the natural technological evolution, but soon they have been replaced by others, paralleling the wavering way new terms are coined in this field. Alternatively, one of the basic, evergreen topic is the search for novel biocatalysts, a research bioprospecting activity which has not been completely substituted but has incorporated in itself the new technological system of knowledge from different fields, acquiring new potency and effectiveness. Novel biocatalysts have been discovered by extensive screening of a large number of microorganisms from Nature thus securing wide biological diversity [1] and fruitful establishment of collections of biocatalysts as tool-boxes has been possible [2]. Metabolomic based high-throughput approaches have become attractive in the discovery of enzyme's function in this context [3].

With respect to traditional screening procedures ignoring microorganisms which cannot be cultivated, taking full advantage of the enormous naturally occurring microbial resources implies the use of an approach based on direct cloning of environmental DNA, a cultivation-independent methodology greatly enhancing the effectiveness of the biocatalyst discovery. In these methodologies DNA is directly isolated from environmental samples and cloned into suitable vectors to construct complex genomic libraries. These libraries can be analyzed for novel genes or pathways using sequence-based techniques or through screening of the enzymatic activities produced in surrogate hosts [4].

Database information on enzymatic activties and stereochemistry has been of great help in the development of biocatalytic protocols for new and existing enzymes, during these years [5].

The uniqueness of marine biocatalysts characterizes their bioprocesses taking advantages by properties such as salt tolerance, hyperthermostability, barophilicity, cold adaptivity, which are habitat-related characteristics of the isolated proteins. Moreover a marine enzyme may carry more, e.g. novel chemical and stereochemical properties. This “chemical biodiversity” increases interest in this field, in fact substrate specificity and affinity play somehow leader roles. Both are evolved properties that are linked to the metabolic functions of the enzymes and to the ecological asset related to natural sources.

Marine sources are represented by microorganisms and fungi, plants and animals, but great efforts are directed towards extremophiles and symbiotic microorganisms and are specially tending to molecular biology tools for production and modification.

This review is intended to give an account of the knowledge about known enzymes of marine origin described in literature thus stimulating future applications that these biocatalysts can offer.