Proximal analysis of the fungus biomass cultivated on sugarcane vinasse and its potential use in aquaculture

Abstract

The need to find a comprehensive solution to the problem of contamination with vinasse in the province of Tucumán is a priority that concerns bothpublic and private organizations. Vinasse is an acidic effluent with high organic load and salinity, and its use for obtaining microbial biomass couldbe an excellent strategy to improve the sustainability of bioethanol plants in the long-term. Filamentous fungi biomass contains large amounts ofcrude protein with essential amino acids that could be used in aquaculture for feed formulations. Therefore, the objective of the present work was toconduct the proximal analysis of the mycelium of a fungus cultivated on sugarcane vinasse to estimate its possible use in fish farming. Themicroorganism was isolated from a soil contaminated with vinasse recollected in the province of Tucumán. The sequence analysis of the 18S rRNAgene showed 100% identity with different species of the genus Aspergillus (accession number NCBI MT165899.1) thereby microorganism wasnamed Aspergillus sp. V2. The 96-h-biomass produced on 50% vinasse added with 1 g/L of KH2PO4 and 2 g/L of (NH4)2SO4 was washed withdistilled water and was lyophilized to determine total proteins by the Kjeldahl-Arnold-Gunning method using the universal factor of conversion toprotein 6.25, total fat (or lipids) by the Soxhlet gravimetric method, crude fiber by the official AOAC method (OMA-Official Methods of Analysis),moisture by heating under reduced pressure, ash by weight difference after calcining the sample, and in carbohydrates indirect form: Totalcarbohydrates = 100 ? (Proteins + Total Fat + Moisture + Ash). Biomass analysis revealed a protein content of 31.7%, 4.72% fat, 15.8% ash, 4.04%crude fiber, 0.1% humidity, and 43.64% carbohydrate. The results obtained demonstrated that the fungus mycelium complies with the basicnutritional properties for aquafeed formulations, with a protein content within the desirable range (from 26% to 55%). The lipid, crude fiber,humidity, ash, and carbohydrates levels were within the standards for aquafeeds reported in the literature. Based on this study, it is concluded that themycelium of Aspergillus sp. V2 produced from vinasse with the addition of nitrogen and phosphorus, constitutes an alternative and low-cost nutrientsource giving added value to a local residue and thus helping to care for the environment.