Optimization of 4,6-α and 4,3-α-Glucanotransferase Production in <i>Lactococcus lactis</i> and Determination of Their Effects on Some Quality Characteristics of Bakery Products

In this study, the production of 4,6-alpha (4,6-alpha-GTase) and 4,3-alpha-glucanotransferase (4,3-alpha-GTase), expressed previously in Lactococcus lactis, was optimized and these enzymes were used to investigate glycemic index reduction and staling delay in bakery products. HP-SEC analysis showed that the relevant enzymes were able to produce oligosaccharides from potato starch or malto-oligosaccharides. Response Surface Methodology (RSM) was used to optimize enzyme synthesis and the highest enzyme activities of 15.63 +/- 1.65 and 19.01 +/- 1.75 U/mL were obtained at 1% glucose, pH 6, and 30 degrees C for 4,6-alpha-GTase and 4,3-alpha-GTase enzymes, respectively. SEM analysis showed that both enzymes reduced the size of the starch granules. These enzymes were purified by ultrafiltration and used to produce bread and bun at an enzyme activity of 4 U/g, resulting in a decrease in the specific volume of the bread. It was found that the estimated glycemic index (eGI) of bread formulated with 4,6-alpha-GTase decreased by 18.01%, and the eGI of bread prepared with 4,3-alpha-GTase decreased by 13.61%, indicating a potential delay in staling. No significant differences were observed in the sensory properties of the bakery products. This is the first study showing that 4,6-alpha-GTase and 4,3-alpha-GTase enzymes have potential in increasing health benefits and improving technological aspects regarding bakery products.