High-Efficiency Conversion of Bread Residues to Ethanol and Edible Biomass Using Filamentous Fungi at High Solids Loading: A Biorefinery Approach  
[PERSON]  
1 Department of Fermentation and Cereals Technology, Wroclaw University of Environmental and Life Sciences, 51-630 Wroclaw, Poland; [EMAIL_ADDRESS]  
[PERSON]  
1 Department of Fermentation and Cereals Technology, Wroclaw University of Environmental and Life Sciences, 51-630 Wroclaw, Poland; [EMAIL_ADDRESS]  
[PERSON]  
2 Swedish Centre for Resource Recovery, University of Borks, 50190 Borks, Sweden; [EMAIL_ADDRESS]  
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acids and antibiotics. Moreover, intensive research in this field proved that FF may also be used for production of other valuable products such as biofuels (ethanol and lipids for biodiesel) [2], food/feed grade biomass with high protein content [3], cell wall-based materials [4] and many others [5] and as the agent for biodegradation of soil/water pollutants [6]. Due to the very high market demands, ethanol and edible biomass are probably the most sought products that may be obtained after edible strains of FF fermentation, and they could be produced simultaneously. Ethanol is primarily used as a gasoline additive (a biofuel) but could also be used as a sole vehicle fuel, and it has many other uses as an extraction solvent, synthesis substrate or hand disinfectant, to list some examples. The interest in alternatives to animal protein sources in human diets is currently increasing due to the growing demand for protein. This demand is caused by the ever-growing human population, increased interest in vegetarian/vegan foodstuffs and environmental concerns regarding animal breeding [7]. Therefore, strains of FF that are used in the production of traditional far-east Asia fermented products such as koji (_Aspergillus oryzae_), tempeh (_Rhizopus_ sp., _Mucor_ sp.) or oncom (_Neurospora intermedia_) could be employed as biocatalysts for simultaneous production of ethanol and food-grade biomass from various organic residuals. The organic residuals of special interest for biorefining processes are various food wastes (both food processing and retail). According to the recent report, estimated food retail, food service and household wastage ranged around 931 million tons in 2019, where respective waste generation branches are responsible for 12.7%, 26.2% and 61.1% of the whole food waste amount [8]. Bakery products residuals (bread, rolls, pastries) represent a significant fraction of the total food waste generation ranging approx. 12% of the total household food leftovers and 18% of the food retail residuals [9]. This suggests that bakery residues are an abundant and renewable resource for FF biorefinery purposes, and bakery retail wastes can be collected as a relatively homogenous mass composed solely of unsold bread [10]. From a technological viewpoint, bread residuals are also an interesting feedstock. Their principal component is starch, which is a carbohydrate that is relatively easy to degrade to produce fermentable sugars (i.e., glucose). Moreover, many of the fungal strains secrete extracellular amylases; thus, the use of external enzymatic preparations might be vastly limited or not needed at all, reducing the total costs of the processing. Additionally, the drying and subsequent grinding of bread residuals requires far less energy use in comparison to grains [11], which may further contribute to the low processing cost of unsold bakery products. Previous reports show that bread residuals could be efficiently converted to various bioproducts.