Exploitation of Agro-Industrial By-Products as Substrate for Solid-State Fermentation

Abstract

The agro-food wastes could be appropriate for use as immobilization carrier in the production of different metabolites with added commercial value by solid-state fermentation (SSF). The objective of this work was the evaluation of the potential of different stone fruit and berry wastes from Romanian food and beverages industry for use as immobilization carrier in SSF. The physical-chemical properties (moisture and water absorption index (WAI)), and the ability of Rhizopus oligosporus and Aspergillus niger to colonize such solid substrates were used as parameters to select the best by-products that could be used successfully in SSF. The agro-food wastes used in this study were derived from Transylvanian local regions and from our laboratory, including kernels and pulp/peels of stone-fruits (plum, apricot) and berry press residues (sea buckthorn , Sambucus nigra (SN) and Sambucus ebulus ).The fungal strains were procured from LGC Standards,Germany. Among the 8 evaluated substrates, only 5 presented higher moisture content than 50%, including apricot peels (AP), residues from plum brandy production (RPBP) (pulp and peel) and berry press residues. The AP and SN berry press residue were the materials with higher WAI values (6.72 and 6.10 (g gel/g dry weight (dw), respectively), whereas the kernels of apricot (2.44 g/g dw) and those from RPBP (2.60 g/g dw) gave the lowest WAI values. The microbiological test showed that the microorganisms ( R. oligosporus and A. niger) had good growth rates when cultivated in berry press residues and stone-fruits pulp/peels. It could be concluded that the stone-fruit agro-industrial by-products (pulp/peel) and berry press residues have great potential to be successfully used as substrate in SSF.