Influence of dairy Penicillium spp. on nutrient content of citrus fruit peel1

The aim of this study is to improve the nutritional value of bergamot fruit peel by solid-state fermentation with three strains of Penicillium camemberti and seven strains of Penicillium roqueforti. To assess the effect of their growth on the chemical composition of the substrate, the following analytical determinations were carried out before and after microbial colonization: crude protein, pure protein, non-proteic nitrogen, dry matter, ether extract, ash, neutral detergent fiber, acid detergent fiber, hemicellulose, cellulose, organic matter, and gross energy. The colonization with the moulds produces substantial changes in the chemical composition of the bergamot fruit peel, notably significant increases in crude protein, ether extract, gross energy, and structural carbohydrates. The solid-state fermentation activity of these moulds could prove a cost-effective way of recycling citrus fruit peel in animal feed, thus increasing its nutritional value by single cell protein. Nevertheless further research on the matter must be carried out, especially on the estimation of the biomass digestibility – in vitro, in sacco or in vivo – and on the check for eventual mycotoxins (roquefortin, cyclopiazoic acid) produced by the moulds in the cellulose waste.