UHMC researchers study how common food preservatives disrupt enzyme activity

Students and researchers at the University of Hawaiʻi Maui College (UHMC) are diving into the effects food preservatives have on enzyme activity inside the mouth with the support of a federally-funded grant program.

Lead researchers on this year’s project, Aliyah Maalea, Samantha “Sam” Termulo and Jarin “Kula” Batangan, presented their findings at the JABSOM Biomedical Sciences Symposium at UH Mānoa and at the Hawaiʻi Branch American Society of Microbiology. Their research specifically focused on how sulfites found in food preservatives inhibit lysozyme activity in the mouth, which may lead to negative health effects.

“There’s a lot of preservatives in the majority of food that we eat,” said Batangan, a lead presenter on the project. “The sulfites, specifically, were our focus because they’re shown to have a big effect on the enzyme activity that’s going on in the mouth. With our research, we wanted to investigate the mechanism of how that happens, because if we understand the mechanisms, then we can better understand ways to counteract that.”

To do this, the group treated human recombinant lysozymes with sulfites, among other methods.

Lysozymes in saliva contain enzymes for breaking down food and play an important role in regulating the mouth’s bacterial ecosystem, or biome, explained Dr. Sally V. Irwin, who is a retired professor of the Cell and Molecular Biology department at UH Mānoa John A. Burns School of Medicine. Irwin also noted that lysozyme is a natural preservative sometimes used in products to prolong shelf life and ensure food safety. She says that understanding lysozymes is imperative to reaching solutions.

This cohort piggybacks off over a decade-worth of studies related to microbiomes and gut health that were conducted at UHMC, many of which were similarly supported through grants from the IDeA Networks of Biomedical Research Excellence (INBRE).

UHMC students and researchers published a major study on gut health in 2017, finding that sulfites in common food preservatives killed or inhibited growth of “good” bacteria, evidence that directly correlated diseases with alterations in the human gut and mouth microbiome. Since then, the aim of their research has evolved, as students and research this past year focused on how to find solutions to the possible side effects of food preservatives. They hoped to achieve this by going straight to the root.

“We had already established that sulfites have an effect on the microbiome, but it’s a whole other area of biochemistry to try to figure out the ways it works,” said Irwin.

Representing a piece of the puzzle, in this latest project, the UHMC researchers analyzed the effect of lysozyme concentration on reaction with sulfites, finding the effect in the mouth was “immediate,” and also analyzed inhibition of lysozyme activity attributed to pH, for which they found a correlation as sulfite increased.

“Since these sulfites are like salts, they kind of take away from the pH in the Goldilocks zone (7.5) and brings it away from its optimal range,” said Aliyah Maalea, a student and contributor on the project. “We found it lowers [enzyme] activity, which we like to have working in our mouths.”

Other lab work in the project included pre-incubation of substrate or lysozyme with sulfites, effects on Km and Vmax and the minimum sulfite for complete inhibition.

One of the reasons Irwin has led studies related to gut health at UHMC is to bring knowledge typically sequestered to a science lab, to the public, to show why it’s important to know how food preservatives, probiotics and antibiotics impact health.

Luz Maria Deardorff, a student and contributor on the project, highlighted the value of understanding these effects, noting that over 80% of neurotransmitters regulating mood are produced by the microbes in the gut, and that 70% of immune cells are housed in the gut.

“Learning about how intimate the connection is between bacteria and symbiosis in our bodies is fundamental knowledge that you shouldn’t go your whole life without understanding it,” said Deardorff.

The full list of contributors to the study, titled “Mechanism of Action of Sulfite Inhibition in Human Recombinant Lysozyme Using Fluorescent Assays” are as follows: Aliya Maalea, Samantha Termulo, Karin Batangan, Francesca Yadao, Luz Maria Deardorff, Michelle Gould (co-coordinator for INBRE program), Dr. Sally Irwin, Dr. Peter Fisher, and Junnie June.