ECO-FRIENDLY BIOCONVERSION OF FRUIT WASTE INTO SINGLE-CELL PROTEIN BY ASPERGILLUS NIGER

Abstract

The increasing demand for sustainable and affordable protein sources has intensified interest in single-cell protein (SCP) production using agro-industrial wastes. This study evaluated the potential of watermelon rind (WR), mango seed kernel (MSK), and their combined formulation (50:50) as substrates for SCP production using Aspergillus niger under solid-state fermentation conditions. The substrates were collected locally, pretreated, and fermented for seven days, followed by optimization of key growth parameters including pH, temperature, and moisture content. Fungal biomass yield and crude protein content were determined using standard analytical methods. Among the tested substrates, the combined MSK: WR formulation produced the highest biomass yield (4.28 ± 0.21 g per 10 g substrate), significantly exceeding yields obtained from MSK (3.62 ± 0.18 g) and WR (2.85 ± 0.12 g). Optimization experiments revealed that maximum SCP production occurred at pH 5.0 (4.31 ± 0.19 g), a temperature of 25 °C (4.34 ± 0.20 g), and 70% moisture content (4.39 ± 0.22 g). Crude protein analysis showed substantial protein enrichment following fermentation, with the highest protein content observed in SCP produced from the combined substrate (51.8 ± 2.1%), followed by MSK (44.9 ± 1.7%) and WR (38.6 ± 1.4%). Statistical analysis confirmed significant differences (p < 0.05) among substrates and fermentation conditions. The findings demonstrate that watermelon rind and mango seed kernel, particularly when used in combination, are effective low-cost substrates for SCP production. This approach offers a sustainable strategy for converting fruit wastes into protein-rich biomass, contributing to alternative protein development and environmental waste reduction.