Growth evaluation of Pycnoporus sanguineus (Fr.) Murr. in agro-industrial residues based on ergosterol concentration in fungal biomass

Description

Agroindustrial wastes are generated in large volumes in Brazil, and reducing the volume of this waste represents economic and environmental interest for industries that aim to consolidate a more sustainable profile. Culturing fungi in the solid phase can be an exciting alternative for transforming solid waste into value-added biomass. Thus, this work evaluated using Pycnoporus sanguineus to reduce the volume of tobacco powder (RPT) and cassava husk flour (CHF) residue. In addition, the fungus growth was examined through the relationship between ergosterol content and mycelial biomass, solving one obstacle to monitoring the process. This work was carried out using solid-state phase cultivation (SSF) and a strain of P. sanguineus isolated from the environment. The substrate used was composed of a mixture of RPT and CHF in a 1:1 (m/m) proportion. The tests were carried out in triplicate at temperatures of 25 °C and 35 °C, with four periodic collections at regular intervals of 17 days (0, 17, 34, and 51 days). The amount of ergosterol in the mycelial mass was determined using a growth curve with P. sanguineus on Sabouraud agar. The volume reduction was estimated from the relationship between the ergosterol content in the samples and mycelial mass. A reduction of 26.32% in volume at a temperature of 35 °C was obtained after 17 days of the process, twice as much as that obtained at 25 °C, demonstrating the influence of temperature on the bioprocess.

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Reagents, solutions, and materials Acetonitrile, hexane, and methanol HPLC grade were purchased from J.T. Baker. Potassium hydroxide and activated carbon, and nylon syringe filters (0.45 μm) were obtained from Synth e Sigma-Aldrich, respectively. The analytical standard of ergosterol (95% purity) was obtained from Sigma Aldrich (St. Louis, USA). Samples: A tobacco industry provided the RPT sample, and the CHF was obtained from an agro-industry in Santa Cruz do Sul/RS, Brazil. Isolation of the fungus Pycnoporus sanguineus: The isolation of the fungus to obtain a pure culture was carried out from the basidiocarp located and collected in a tree trunk present in the external area of the University of Santa Cruz, Santa Cruz do Sul, RS-Brazil (29⁰41'50.55''S; 52⁰26' 06.08''O). Methods: Solid-state fermentation; Quantification of ergosterol in microbial biomass was based on alkaline hydrolysis and liquid-liquid extraction.

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