Research on the origin and the side effects of chitosan stabilizing properties in wine

Abstract

Fungal chitosan is a polysaccharide made up of glucosamine and N-acetyl-glucosamine and derived from chitin-glucan of Aspergillus niger or Agaricus bisporus. Fungal chitosan has been authorized as an antiseptic agent in wine since 2009 (OIV) and in organic wine in 2018. At the maximum dose of 10g/hl, it was shown to eliminate Brettanomyces bruxellensis, the main spoilage agent in red wines. Fungal chitosan is highly renewable, biocompatible (ADI equivalent to sucrose) and non-allergenic. However, winemakers often prefer to use sulfites (SO2), though sulfites are classified as priority food allergens, than chitosan. Indeed, many conflicting reports exist regarding its efficiency and its side effects towards beneficial wine microorganisms or wine taste. These contradictions could be explained by the heterogeneity of the fungal chitosan lots traded, the diversity of the wines (chemical composition, winemaking process), but also, by the recently highlighted huge genetic diversity prevailing in wine microbial species. 

The CHITOWINE project (ANR 17-CE21-0006) is based on the collaboration of three academic partners, a technology transfer unit and an industrial partner. It primarily aims to better define the potential and limitations of fungal chitosan use as an antimicrobial agent in wine. The work will first enable to better define the spectrum of fungal chitosan through the screening of a large microbial collection representative of the inter- and intra-specific diversity of wine ecosystem (more than 200 strains in 17 species of yeasts and bacteria). The chemical characteristics essential to the antiseptic activity of fungal chitosan (degree of acetylation, molecular weight, solubility and charge) and the influence of extrinsic parameters of reaction (pH, temperature, and dose) will be also evaluated. In addition, the physiological effects of chitosan will be sought through biochemical, microscopic and transcriptomic tests, to identify, if possible, the molecular targets of chitosan and to understand the sensitivity differences observed, between inter or intra species and between strains in the same species. Based on these results, improved use recommendation will be proposed and evaluated. Analytical methods to guide chitosan use will be developed and optimized.