Brewing process development by integration of edible filamentous fungi to upgrade the quality of brewer’s spent grain (BSG)

Brewer’s spent grain (BSG) is the main solid by-product of the brewing sector. High moisture and nutrient-rich content render BSG easily perishable, leading to waste generation and environmental impacts. BSG has narrow applications in both feed and food sectors due to its composition including high fiber and low protein. Therefore, a processing strategy leading to the nutritional valorization of BSG could widen its applications. In this study, submerged cultivation of edible filamentous fungi (Aspergillus oryzae, Neurospora intermedia, and Rhizopus delemar) was introduced as a strategy to enhance the protein content of BSG. The growth of all strains in BSG increased the protein content of the fermented BSG. The highest increase of protein content (from 22.6% to 34.6%), was obtained by cultivation using A. oryzae and medium supplementation. The protein content increase was followed by a decrease in the content of polysaccharides (up to ca. 50%), namely starch, glucan, xylan, and arabinan. The addition of cellulase resulted in enhanced ethanol production from BSG but led to lower concentration of recovered solids. In conclusion, simple processing of BSG using edible filamentous fungi can lead to quality improvement of BSG, providing potential economic and environmental benefits to the brewing sector.

New Insights on Protein Recovery from Olive Oil Mill Wastewater through Bioconversion with Edible Filamentous Fungi

Olive oil mills represent an important sector in the Mediterranean Sea Basin but also an environmental hazard due to untreated wastewater. Recovery of nutrients from olive oil mill wastewater (OMWW) as protein-rich microbial biomass can produce novel feed and reduce its chemical oxygen demand; however, low-protein containing products have been reported. New strategies leading to higher protein-containing fungal biomass could renew the research interest on bioconversion for pollution mitigation of OMWW. In this work, through cultivation of edible filamentous fungi (Aspergillus oryzae, Neurospora intermedia, and Rhizopus delemar), a link between the protein content in the originated fungal biomass, and the addition of nitrogen and medium dilution was established. Addition of nitrogen in the form of NaNO3 reduced the cultivation time from 96 h to 48 h while achieving a similar biomass mass concentration of 8.43 g/L and increased biomass protein content, from w = 15.9% to w = 29.5%. Nitrogen addition and dilution of OMWW, and consequent reduction of suspended solids, led to an increase in the protein content to up to w = 44.9%. To the best of our knowledge, the protein contents achieved are the highest reported to date and can open new research avenues towards bioconversion of OMWW using edible filamentous fungi.