Guntima Suwannapong

The western honey bee (Apis mellifera L.) and the stingless bee (Tetragonula pagdeni, Schwarz, 1939) are important managed pollinators of crops and wild plants. Their activities support agricultura...

Apis dorsata honey is a rich source of natural antioxidants and antibacterial compounds. Thermal processing is commonly used to improve honey fluidity and delay crystallization; however, it may also affect bioactive properties and promote the formation of 5-hydroxymethylfurfural (5-HMF). We evaluated the impact of temperature regimes on biological activities and 5-HMF contents of A. dorsata honey. Honey samples were collected from A. dorsata colonies. Honey color, total phenolic content (TPC), total flavonoid content (TFC), 5-HMF content, and antibacterial activity against Escherichia coli and Staphylococcus aureus were investigated after being treated at room temperature, 55 °C, 65 °C, 75 °C, and 85 °C for 0.5, 1, and 2 h. Heating at 55 °C, 65 °C, 75 °C, and 85 °C significantly enhanced color intensity, TPC, and TFC. Samples treated at 85 °C for two hours showed the highest antioxidant activity, with an EC₅₀ significantly lower than that of the others (51.31 ± 0.77 mg/mL). Conversely, 5-HMF content increased markedly with increasing exposure temperature and time. Antibacterial assays revealed that all treated samples inhibited E. coli, whereas no inhibitory activity was detected against S. aureus. These results define important processing parameters in food safety for heating honey to preserve bioactivity integrity without loss in quality and maintenance of product stability and sustainability.

Ethanolic extracts of propolis collected from Apis mellifera hives have been shown to reduce Nosema ceranae infection in honey bee workers. This study aimed to determine the propolis concentration that optimizes the control of N. ceranae infection in honey bee workers. Newly emerged worker bees were individually fed 2 μL of 50% sucrose solution (w/v) containing 105 N. ceranae spores per bee, and treated with 0%, 25%, 50%, and 75% ethanolic extracted propolis in 50% sucrose solution (v/v). The treated bees were maintained in cages at 34 ± 2˚C and 55 ± 5% RH throughout the study. The number of dead bees was counted and removed from the cages daily for 30 days to generate survival curves. The number of N. ceranae spores per bee (infectivity) was quantified using a hemocytometer, and the number of infected bees per hundred bees (infection rate) was determined. The survival rates of N. ceranae infected bees fed 25%, 50%, and 75% propolis (NP1, NP2, NP3, respectively) were significantly higher than those of infected bees not fed propolis (NO). Furthermore, the infectivity and infection rates of NP2 and NP3 groups were significantly lower than those of the NO group. The infectivity and infection rates of the NP1 group were not different than those of the NO group. Our data suggest that 50% and 75% propolis extracts are appropriate concentrations for treating N. ceranae infection in honey bees. Ethanolic extracted propolis can be an alternative treatment for N. ceranae infection in Western honey bees.

Nosema ceranae is a microsporidian that infects Apis species. Recently, natural compounds have been proposed to control nosemosis and reduce its transmission among honey bees. We investigated how ethanolic extract of Tetrigona apicalis’s propolis and chito-oligosaccharide (COS) impact the health of N. ceranae-infected Apis dorsata workers. Nosema ceranae spores were extracted from the guts of A. florea workers and fed 10⁶ spores dissolved in 2 µL 50% (w/v) sucrose solution to A. dorsata individually. These bees were then fed a treatment consisting either of 0% or 50% propolis extracts or 0 ppm to 0.5 ppm COS. We found that propolis and COS significantly increased the number of surviving bees and lowered the infection ratio and spore loads of N. ceranae-infected bees 14 days post-infection. Our results suggest that propolis extract and COS could be possible alternative treatments to reduce N. ceranae infection in A. dorsata. Moreover, N. ceranae isolated from A. florea can damage the ventricular cells of A. dorsata, thereby lowering its survival. Our findings highlight the importance of considering N. ceranae infections and using alternative treatments at the community level where other honey bee species can act as a reservoir and readily transmit the pathogen among the honey bee species.

Nosema ceranae is a unicellular microsporidian causing ventricular cell lysis in host Apis species. We hypothesized that the gut microbiota of honey bees, A. cerana, A. dorsata, A. florea, and A. mellifera, is disrupted by N. ceranae infection. Correspondingly, we investigated the impact of N. ceranae infection on gut populations of Bifidobacterium sp. and Apilactobacillus kunkeei in the selected Apis species. The bacteria populations were compared using a culture-dependent method and employing 16S rRNA gene sequencing between bees infected with 2.0 × 10⁵N. ceranae spores and those remaining uninfected. The number of N. ceranae spores per bee and the ratio of infected gut cells to uninfected cells were measured at five and ten days post infection (p.i.). N. ceranae spore load at ten days p.i. was significantly greater than at five days p.i. and was varied with species’ body size. For each of the four Apis species, N. ceranae treated bees had lower survival than did the control bees. Moreover, A. florae had the largest infection ratio of all the species. Across all Apis species, N. ceranae infected individuals had significantly lower mean numbers of Bifidobacterium sp. and A. kunkeei than did uninfected ones. Among infected bees, the average number of both bacteria was significantly greatest in A. dorsata and lowest in A. cerana. Overall, N. ceranae infection was associated with histopathological damage and also with lower populations of Bifidobacterium sp. and A. kunkeei in the midguts of the tested honey bee species.