The Effect of Diet on the Composition and Stability of Proteins Secreted by Honey Bees in Honey.

Oleg Lewkowski,Dirk Dobritzsch,Silvio Erler,Carmen I Mureșan,Matthew Fuszard

doi:10.3390/insects10090282

Abstract

Honey proteins are essential bee nutrients and antimicrobials that protect honey from microbial spoilage. The majority of the honey proteome includes bee-secreted peptides and proteins, produced in specialised glands; however, bees need to forage actively for nitrogen sources and other basic elements of protein synthesis. Nectar and pollen of different origins can vary significantly in their nutritional composition and other compounds such as plant secondary metabolites. Worker bees producing and ripening honey from nectar might therefore need to adjust protein secretions depending on the quality and specific contents of the starting material. Here, we assessed the impact of different food sources (sugar solutions with different additives) on honey proteome composition and stability, using controlled cage experiments. Honey-like products generated from sugar solution with or without additional protein, or plant secondary metabolites, differed neither in protein quality nor in protein quantity among samples. Storage for 4 weeks prevented protein degradation in most cases, without differences between food sources. The honey-like product proteome included several major royal jelly proteins, alpha-glucosidase and glucose oxidase. As none of the feeding regimes resulted in different protein profiles, we can conclude that worker bees may secrete a constant amount of each bee-specific protein into honey to preserve this highly valuable hive product.

Highlights

Honey, the carbohydrate source for honey bee colonies, is produced by in-hive worker bees through a process of ripening foraged nectar, honeydew or other sweet plant saps until long-storable honey is obtained [1,2]
Carbohydrates, minerals, amino acids, plant secondary metabolites and proteins can be found in variable amounts, each being characteristic of specific honey types
We focus on investigating nutritional factors influencing both protein composition and quantity in the process of honey ripening

Summary

Introduction

The carbohydrate source for honey bee colonies, is produced by in-hive worker bees through a process of ripening foraged nectar, honeydew or other sweet plant saps (e.g., inversion of sugar) until long-storable honey is obtained [1,2]. Carbohydrates (mainly glucose and fructose), minerals, amino acids, plant secondary metabolites and proteins can be found in variable amounts, each being characteristic of specific honey types. Proteins detectable in honey (0.58–7.86% [3]) are mainly secreted from salivary and hypopharyngeal glands of forager and in-hive bees [4] and might be of minor. Insects 2019, 10, 282 relevance for larval and adult bee nutrition. The nutritive value of honey proteins is not clear and needs to be investigated in future studies, and alternative health-enhancing and developmental functions of honey proteins for larvae and adult bees are possible. It is known that pollen is the main protein and amino acid source for bees to facilitate gland development and brood rearing. Two major groups of bee-secreted proteins are omnipresent in all types of honey:

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Discussion

Conclusion