Abstract
PurposeNovel protein sources are urgently needed to meet the increasing protein demand of a continuously growing world population. This study is focused on the production of protein rich mushroom mycelia on industrial side streams.MethodsSubmerged propagation of mushrooms was carried out in shake flasks which contained agro-industrial side streams as the sole carbon source. The biomass obtained was analyzed for its crude protein, ash and fat content as well as for its fatty acid and amino acid profiles. Vitamin D2 production from ergosterol in the biomass was induced by UV-B irradiation and determined by HPLC–DAD. The share of fungal mycelium in the total biomass was determined by extraction and quantitation of ergosterol. Additionally, water and oil binding capacity (WBC and OBC) were evaluated.ResultsA screening of basidiomycetes grown on agro-industrial side streams indicated a fast growth of Pleurotus sapidus on apple pomace. After 4 days of cultivation, the biomass obtained from this mushroom–substrate combination contained 21% true protein in dry matter. In addition to proteins, the amounts of lipids (4%), ash (2%) and carbohydrates (74%) were quantitated. The dominating fatty and amino acids of Pleurotus sapidus grown on apple pomace were linoleic acid and glutamic acid/glutamine, respectively. Concentrations of up to 115 µg (g dry matter)−1 vitamin D2 were formed from ergosterol by UV-B irradiation. Ergosterol was used as a biomarker to monitor the amount of fungal content.ConclusionThe nutritional value of agro-industrial side streams such as apple pomace can be upcycled by biotransformation with basidiomycetes.
Highlights
Fungi have been considered as a desirable source of human nourishment for thousands of years
Limits of detection (LOD) and of quantitation (LOQ) were calculated based on DIN 32645 resulting in a LOD of 7.06 μg mL−1 and a LOQ of 25.10 μg m L−1, corresponding to 53.2 and 188.3 μg (g DM)−1, respectively
For determining the ergosterol amount of pure fungal biomass, the basidiomycete was cultivated in malt extract medium (20 g L−1), and the mycelium was harvested and lyophilized as described above
Summary
Fungi have been considered as a desirable source of human nourishment for thousands of years Because of their high nutritional value and pleasant taste, the fruiting bodies of mushrooms are commonly consumed. They are rich in fiber (i.e., chitin and glucan), contain all essential amino acids, vitamin D2, several vitamins of the B group, and have low fat contents (Manzi et al 1999). Due to their low energy content, they represent an ideal food for low calorie diets. Prominent examples include tempeh, which is produced by fermentation of soy beans with the mucoromycete Rhizopus oligosporus, and QuornTM which is based on the
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