Enzymes for sugar reduction from marine microbial diversity

Sugar consumption is a major public health concern, being strongly associated with obesity, type 2 diabetes, and cardiovascular disease. Strategies to reduce sugar intake without compromising the sensory and technological properties of foods and beverages are therefore highly desirable. Enzymes offer a promising approach to this end.

To assess the potential of the marine microorganisms from the REGENERA collection to produce such enzymes, we analyzed the genomes of 559 strains. The genomes were annotated with Bakta, and the abundance of genes of interest was evaluated in the genome annotations. We identified a diverse repertoire of genes, totaling 9531 hits. The enzymatic activities evaluated and the number of hits for each were:

1. Oxidative enzymes for glucose conversion – 1531 hits, comprising quinoprotein glucose dehydrogenase [78], glucose 1-dehydrogenase [1438], glucose-fructose oxidoreductase [5] and glucose-6-phosphate 1-dehydrogenase [10];

2. Glucosyltransferases for in situ fiber generation – 484 hits, comprising dextransucrase [1], amylosucrase [2], levansucrase [399], sucrose phosphorylase [71] and cyclomaltodextrin glucanotransferase [11];

3. Epimerases and isomerases for rare sugar production – 4509 hits, comprising D-tagatose/L-ribulose/D-psicose 3-epimerase [20], L-arabinose isomerase [358], xylose isomerase [959], L-rhamnose isomerase [71], mannose-6-phosphate isomerase [952], glucose-6-phosphate isomerase [564], ribose-5-phosphate isomerase [446], galactose-6-phosphate isomerase [8], UDP-glucose 4-epimerase [1127] and cellobiose epimerase [4];

4. Invertases and sucrose-hydrolyzing enzyme systems – 430 hits, comprising beta-fructofuranosidase [14], sucrose phosphorylase [71] and alpha-glucosidase [345]; and

5. Sugar-metabolizing enzymes of lactic acid bacteria – 2577 hits, comprising beta-galactosidase [598], 6-phospho-beta-galactosidase [84], tagatose-6-phosphate kinase [1], tagatose-1,6-diphosphate aldolase [3], galactokinase [406], galactose-1-phosphate uridylyltransferase [115], UDP-glucose–hexose-1-phosphate uridylyltransferase [406], glucokinase [500] and phosphoenolpyruvate–protein phosphotransferase [464].

Overall, the analyzed strains harbor a wide variety of enzymes with potential for sugar reduction. We also compared the identity of these enzymes against those available in public databases (UniRef90), aiming to identify enzymes with low identity to those already described. Low identity may reflect structural variations, with consequent differences in specificity, stability, catalytic efficiency, and other properties. Classical studies indicate that function, particularly substrate specificity, is reliably conserved only above approximately 40% identity, while 60% or more is typically used for complete enzyme classification, and 80–90% identity indicates redundancy. In our analysis, we found 81 enzymes with 60–70% identity, 31 with 50–60% identity, and 3 with 40–50% identity. These low-identity hits may represent opportunities for functional variation or innovation in enzyme activity.

Predictions must now be validated experimentally through heterologous expression, enzymatic assays, and testing in relevant food matrices. Finally, the most promising strains identified could be further improved through strain optimization strategies, such as metabolic engineering to enhance enzymatic activity and industrial performance.

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