Differential Processing of Sucrose and Invert Syrup in Honey Bees

Feeding bees carbohydrates, as a substitute for nectar, has become essential in modern beekeeping. We compared the effects of 65% sucrose (SS) and 65% invert sugar (IS) syrups on the survival and enzyme activity of caged honey bees. Specifically, we analyzed glycosidase activity in the head and midgut of the bees and compared the composition of sucrose-based (SH) and invert sugar-based (IH) "honey" stored by the bees and collected from the comb. Glycosidase activity was similar in head in contrast to midgut where it was higher in IS fed bees, which appeared to be residual yeast β-fructofuranosidase activity. Fructose to glucose ratio in SH were 60.84/39.16 and a presence of some other sugars were detected, while ratio in IH were 48.49/51.51, almost exactly the same as in start fed (IS) (48.57/51.43). It has been demonstrated that glycosidase activity in IH was residual yeast β-fructofuranosidase activity. Zymogram detected α-amylase band in SH, in contrast to IH, which suggest that honey bees do not add amylase into IS. In contrast to SH, no crystallization occurred in IH. SS and IS densities were 1.23 and 1.24 g/mL, respectively, increasing to 1.35 g/mL in SH and 1.28 g/mL in IH after processing. This suggests that higher humidity and restricted cleansing flight make it harder for bees to remove excess water from IH, leading to increased midgut and hindgut weight, which correlates with higher mortality in the third week for the IS-fed group and fourth week for the SS-fed group.