Optimizing medium composition with wastewater from Coffea arabica processing to produce single-cell protein using Candida sorboxylosa

Background: Coffee production is an important agro-industrial activity in several countries worldwide. However, during wet processing of coffee beans, substantial quantities of wastewater effluents are generated and discharged into nearby water systems, negatively impacting ecosystems. A compelling biotechnological alternative involves the use of nutrients contained in wastewater (e.g., sugars, proteins, and salts) to produce value-added molecules–such as single-cell protein (SCP) using the yeast Candida sorboxylosa–with high potential for use as animal feed. Results: Yeast isolated from the feces of ring-tailed coatis showed a positive assimilation of reducing sugars (glucose, mannose, and fructose). Efficient reuse of coffee wastewater (CWW) for SCP production was achieved via the statistical design of experiments (DoE) technique. The bioprocess was standardized in a medium culture composed of 87.5% (v/v) CWW, and of 1.38 and 7.24 g/L yeast extract (YE) and ammonium sulfate [(NH₄)₂SO₄], respectively, resulting in a high SCP yield of approximately 38%. Conclusion: The reuse of CWW shows potential as a low-cost component for SCP production that can ultimately reduce the environmental impact of wastewater effluent by circumventing its release into river systems. The bioprocess developed in this study presented certain advantages, including high volumes of CWW with only YE and (NH₄)₂SO₄ supplementation, and without requiring additional components to correct the pH of the medium. Therefore, it is highly feasible to apply this bioprocess in close proximity to coffee-processing agrobusinesses, thus generating an alternative source of income for Peruvian coffee-producing communities.