**Preface to "Marine Enzymes"**

Prominent conclusions by many scientists in the field of marine biotechnology emphasize that, due to marine biological diversity and to the specificity of biological marine metabolisms, the study of biocatalysts on a global scale from this environment is just starting, and possesses huge potential for the development of applications with industrial benefits. The oceans are the world's largest ecosystem with a biodiversity undescribed by science, at a degree more than 90%. Only a deep understanding of the complexity of this ecosystem will enable human beings to protect the oceans and organisms populating them, and pave the way for the sustainable exploitation of marine resources. This knowledge constitutes the core of marine biotechnology, and will certainly fuel various applications. Many fields are covered that are highly relevant to societal challenges: (i) in a biorefinery value-chain with marine enzymes for biochemical processes; (ii) in food industries for enzymatic procedures in seafood processing; (iii) in fields of fine chemicals—in pharmaceutical, cosmetics, agriculture and environmental sectors—enzymatic treatments are a tool to improve efficiency and selectivity for extraction/manipulation of structurally complex marine molecules, to gain access to bioactive compounds, and to provide complex core blocks for hemisynthesis; (iv) the field of marine biomarkers and applications in pollution monitoring (biosensor) and bioremediation could also be of high significance for the appreciation of marine sources for enzymes. However, many challenges remain, including a deep comprehension of the "marine biotechnology landscape" and a multidisciplinary approach, not only in education and training.

This book starts with two review articles—in the first, a refined search of literature is adopted with respect to previous surveys, centering generally on the enzymatic process more than on a single novel activity developing the analysis, according to the biotechnological field of applications; in the second, a more selective overview of the state of the art in marine and freshwater microalgal enzymes with potential biotechnological applications is provided, discussing future perspectives for this field. With recent advances, in fact, it is becoming easier to identify sequences encoding targeted enzymes, increasing the likelihood of the identification, heterologous expression, and characterization of these enzymes of interest, by genomics and transcriptomic approaches.

A list of six articles is dedicated to a specific enzymatic activity, alginate lyase, that is important in the production of alginate oligosaccharides for their recognized activities as anticoagulants, antioxidants, antineoplastics, plant growth accelerators and tumor inhibitors, in food, agricultural, and medical fields. The great biodiversity of marine source is important for the urgency to obtain alginate lyases with the optimal characteristics (e.g., pH-stability, thermo-tolerance, and single product distribution) needed for industrial applications.

A further batch of six articles are always dedicated to carbohydrate active marine enzymes, including two other additional reports on galactosidases, thus totalling more than half a book dedicated to this class of enzymes.

Among the interesting other-articles, the one reporting the asymmetric reduction of ketones using the growing and resting cells of 13 marine-derived fungi shows the importance of these organisms in this field and the possibility of adopting a simple system that offers alternative, highly enantioselective and minimally polluting properties to important enantiomeric pure alcohols.

> **Antonio Trincone** *Editor*
