The beeswax processing by-product: a potential antibacterial ingredient for food and nutraceutical applications

The purification of raw beeswax by melting produces a semi-solid beeswax by-product (BBR) composed by honey, resins and other constituents that is usually considered as a waste. In this article, the chemical characterisation of BBR is reported, with the aim to valorise this by-product following the principles of the circular economy. Carbohydrates, hydrocarbons and minerals were among the main constituents. Flavonoids and phenolic acids represent 1.5% of the BBR, and their qualitative profile resembles the propolis. To assess its potential usefulness, the BBR was tested against gram-positive and gram-negative bacteria of clinical interest, and results were compared with the raw propolis. Klebsiella pneumoniae and Salmonella enterica were inhibited at concentrations >= 0.001 mg mL(-1), while Enterococcus faecalis and methicillin-resistant Staphylococcus aureus from 0.01 mg mL(-1). Only BBR was active on Pseudomonas aeruginosa. Below the concentration of 1 mg mL(-1), no significant toxicity on Caco2 cells was observed. These results indicate that the BBR presents a polyphenol composition similar to propolis and a significant antibacterial activity. Thus, on the basis of these results, we suggest that the BBR can represent a sustainable alternative to propolis as food preservative or nutraceutical.