Clement Niyirora | ALES Graduate Seminar

A graduate exam seminar is a presentation of the student’s final research project for their degree.
This is an ALES MSc Final Exam Seminar by Clement Niyirora. This seminar is open to the general public to attend.

Thesis Topic: Characterization of Dextransucrase and Branching Sucrase of Apilactobacillus kunkeei DSM 12361

MSc with Dr. Michael Gaenzle.

Seminar Abstract:

Glycoside hydrolase family 70 (GH 70) glucansucrases have various applications in both the food and non-food industries. This study reports the characterization of two GH 70 enzymes, dextransucrase and branching sucrase, of Apilactobacillus kunkeei DSM 12361 on a range of acceptor substrates. GtfZ of A. kunkeei DSM 12361 possesses two catalytic domains, CD1 and CD2, which are interconnected by a glucan binding domain (GBD). For this study, dextransucrase CD1-GBD is a combination of the first catalytic domain CD1 with GBD, while branching sucrase GBD-CD2 is composed of GBD combined with the second catalytic domain CD2. In addition to sucrose as the sole substrate, CD1-GBD was active when dextran was available as an acceptor substrate. It was also found that CD1-GBD was active on reuteran and modified potato amylose. GBD-CD2 was also observed to be active on various substrates such as dextran, reuteran, and modified amylose, which proves the ability of GBD-CD2 to introduce branches on polymer chains with different linkage types. The activity of CD1-GBD and GBD-CD2 showed a preference for α-(1→6) glycosidic linkage in the acceptor substrate. The ability of CD1-GBD and GBD-CD2 to act on starch-derived molecules such as potato amylose is crucial in synthesizing polymer at a low cost. The activity on a wide range of substrates increases the options for producing polymers with different properties.