BackThus, cellulose and chitin, the annual net production of which are estimated to be billions of tons, have recently become potential renewable sources for the production of biofuel. They can be used for powering gasoline vehicles as well as in providing essential chemical compounds for the food and pharmaceutical industry according to Mikhail Kurashin’s (PhD) recently defended doctoral thesis[1].
The thesis defended at the University of Tartu focuses on substrates (cellulose and chitin), enzymes (cellulases and chitinases), and their interactions. What is more, it introduces the methods for the measurement of cellulase and chitinase processivity.
Processivity is defined as the ability of an enzyme to conduct sequential catalytic acts without dissociating from its substrate. It is therefore an important characteristic of cellulose/chitin degrading enzymes. “Investigating it is essential because knowledge about the enzymes could provide a good clue to improving the process of recalcitrant polysaccharides’ saccharification,” Kurashin explained.
Three Ways for getting to know Enzymes
He noted that although natural enzymes are capable of completely solubilising cellulose and chitin, their application on an industrial scale is still not cost-efficient and it explains why biofuels cannot compete with fossil transportation fuels to date. Natural enzymes are slow and the construction of improved enzymes that can be adapted for industrial uses is required.
Naturally, the construction of improved enzymes involves many components and steps but Kurashin and his colleagues took one step at a time. They constructed and developed three methods that could be used to measure the processivity and other kinetic parameters of the enzymes, and might therefore contribute to understanding the ways in which enzymes must be improved.
Two methods, namely single-hit and single-turnover experiments, are aimed at measuring processivity. The third method, substrate exchange experiment, is intended for measuring the dissociation rate constant. The latter is closely related to processivity. A detailed description of all methods is available in the doctoral thesis.
Many Possibilities for Further Research
Kurashin found the topic of cellulases and chitinases quite casually. His friend and coursemate invited him to join the lab of Professor Juhan Sedman in 2005, when Kurashin was a second-year student. At that time the group of Priit Väljamäe (supervisor of Kurashin) worked at Sedman’s lab but had its own field of research (studying cellulases and chitinases). By the year 2005 Väljamäe’s group was looking for students and Kurashin joined it. “The deeper I dug, the more the topic started to interest me,” Kurashin said.
Today when his doctoral thesis has been defended, Kurashin has not yet decided whether he will continue the research on cellulases and chitinases or change his field of study.
He certainly has many ideas. There are a lot of potential applications for chitinases and cellulases to be adapted to human needs, Kurashin said. “Of course, the most popular topic is improving the process of biofuel production. But besides that, cellulases and chitinases can be employed to produce small sugar molecules that in turn are the source material for prebiotics. It has been also demonstrated that the human organism produces two chitinases that play an important role in antifungal response,” he explained. Kurashin added that researching chitinases can potentially provide us with a clue to achieving a better quality of life.
According to Kurashin, new methods for the measurement of processivity and other important parameters have to be developed in the kinetics of cellulases and chitinases. There are not enough contemporary methods and new ones are crucial for the better understanding of molecular mechanisms employed by chitinases and cellulases.
[1]Kurašin, M. (2017) Processivity of cellulases and chitinases. URL: https://dspace.ut.ee/bitstream/handle/10062/55507/kurasin_mihhail.pdf?sequence=5&isAllowed=y
This article was funded by the European Regional Development Fund through Estonian Research Council.
