Waste management systems are overloaded with huge streams of plastic, a large part of this being originated from packaging. Additionally, the production of wheat, one of the most cultivated crops in the world, generates low-value lignocellulosic materials, which are mostly discarded. In this study, the wheat lignocellulosic byproducts straw and bran were used for the co-production of enzymes and bio-based materials with possible application as packaging via the compression molding method. The mechanical properties of the films were studied based on the effects of the removal of lignin by alkali and biological pretreatment, the growth of filamentous fungi, the size of the particles, and the enzyme recovery. Generally, the straw films were stiffer than the bran ones, but the highest Young’s modulus was obtained for the biologically pretreated bran (1074 MPa). The addition of a step to recover the fungal cellulases produced during the cultivation had no statistical effect on the mechanical properties of the films. Moreover, alkali and biological pretreatments improved the anaerobic biodegradability of the straw films. Thus, the wheat bran and straw can be used for the co-production of enzymes, materials, and biogas, potentially changing how wheat and packaging wastes are managed.

The term mycoprotein refers to the protein-rich food made of filamentous fungal biomass that can be consumed as an alternative to meat. In this paper, the impact caused by the substitution of animal-origin meat in the human diet for mycoprotein on the health and the environment is reviewed. Presently, mycoprotein can be found in the supermarkets of developed countries in several forms (e.g. sausages and patties). Expansion to other markets depends on the reduction of the costs. Although scarce, the results of life cycle analyses of mycoprotein agree that this meat substitute causes an environmental impact similar to chicken and pork. In this context, the use of inexpensive agro-industrial residues as substrate for mycoprotein production has been investigated. This strategy is believed to reduce the costs involved in the fungal cultivation and lower the environmental impact of both the mycoprotein and the food industry. Moreover, several positive effects in health have been associated with the substitution of meat for mycoprotein, including improvements in blood cholesterol concentration and glycemic response. Mycoprotein has found a place in the market, but questions regarding the consumer's experience on the sensory and health aspects are still being investigated.

Self-binding ability of the pectin molecules was used to produce pectin films using the compression molding technique, as an alternative method to the high energy-demanding and solvent-using casting technique. Moreover, incorporation of fungal biomass and its effects on the properties of the films was studied. Pectin powder plasticized with 30% glycerol was subjected to heat compression molding (120 °C, 1.33 MPa, 10 min) yielding pectin films with tensile strength and elongation at break of 15.7 MPa and 5.5%, respectively. The filamentous fungus Rhizopus oryzae was cultivated using the water-soluble nutrients obtained from citrus waste and yielded a biomass containing 31% proteins and 20% lipids. Comparatively, the same strain was cultivated in a semi-synthetic medium resulting in a biomass with higher protein (60%) and lower lipid content (10%). SEM images showed addition of biomass yielded films with less debris compared to the pectin films. Incorporation of the low protein content biomass up to 15% did not significantly reduce the mechanical strength of the pectin films. In contrast, addition of protein-rich biomass (up to 20%) enhanced the tensile strength of the films (16.1–19.3 MPa). Lastly, the fungal biomass reduced the water vapor permeability of the pectin films.

The process to obtain starch from wheat requires high amounts of water, consequently generating large amounts of wastewater with very high environmental loading. This wastewater is traditionally sent to treatment facilities. This paper introduces an alternative method, where the wastewater of a wheat-starch plant is treated by edible filamentous fungi (Aspergillus oryzae and Rhizopus oryzae) to obtain a protein-rich biomass to be used as e.g. animal feed. The wastewater was taken from the clarified liquid of the first and second decanter (ED1 and ED2, respectively) and from the solid-rich stream (SS), whose carbohydrate and nitrogen concentrations ranged between 15 and 90 and 1.25–1.40 g/L, respectively. A. oryzae showed better performance than R. oryzae, removing more than 80% of COD after 3 days for ED1 and ED2 streams. Additionally, 12 g/L of dry biomass with protein content close to 35% (w/w) was collected, demonstrating the potential of filamentous fungi to be used in wastewater valorization. High content of fermentable solids in the SS sample led to high production of ethanol (10.91 g/L), which can be recovered and contribute to the economics of the process.

The food industry, one of the most important industrial sectors worldwide, generates large amounts of biodegradable waste with high organic load. In recent years, the traditional management methods to treat this waste (e.g., landfilling) have been considered not suitable because they do not exploit the potential of the waste material. Alternatively, valorization of food industry waste via a biorefinery model using filamentous fungi is considered to represent an attractive strategy because it minimizes the negative impacts while recovering the nutrients and energy of the waste, in accordance with the concept of the circular economy.

In this thesis, four food processing wastes were utilized as case studies: potato protein liquor (PPL, the soluble fraction of potato starch production waste), the peels wasted during orange juice production, the starchy byproduct of pea protein processes, and the wastewater of a wheat-starch plant. Rhizopus oryzae, a zygomycetous filamentous fungus, was grown with these wastes as a substrate, yielding biomass containing 43% (w/w) protein together with 51% removal of the chemical oxygen demand when cultivated in tenfold-diluted PPL. Moreover, protein-rich biomass was produced using the pea-processing byproduct (55%) and wheat-starch wastewater (51%). In contrast, cultivation in orange peel extract yielded a biomass rich in lipids (20%). The use of PPL was also studied in terms of the economy of fungal cultivation. The biotreatment was found to require only 46% of the capital investment necessary for treating PPL by the traditional strategy (application as fertilizer). In comparison, the ascomycetous fungus Aspergillus oryzae yielded superior results compared to those of R. oryzae when grown in the starchy residues. The high protein content of the fungal biomass encouraged the investigation of its use for bioplastic production. The addition of 20% fungal biomass in a pectin matrix increased the tensile yield of the film and reduced the elongation at break. Moreover, a positive effect on water vapor permeability of the film was also observed.

These results indicate the ability of the filamentous fungi to convert resources wasted by the food industry into new products with positive impacts on the economy and the environment.

Background

Currently around one billion people in the world do not have access to a diet which provides enough protein and energy. However, the production of one of the main sources of protein, animal meat, causes severe impacts on the environment. The present study investigates the production of a vegan-mycoprotein concentrate from pea-industry byproduct (PpB), using edible filamentous fungi, with potential application in human nutrition. Edible fungal strains of Ascomycota (Aspergillus oryzae, Fusarium venenatum, Monascus purpureus, Neurospora intermedia) and Zygomycota (Rhizopus oryzae) phyla were screened and selected for their protein production yield.

Results

A. oryzae had the best performance among the tested fungi, with a protein yield of 0.26 g per g of pea-processing byproduct from the bench scale airlift bioreactor cultivation. It is estimated that by integrating the novel fungal process at an existing pea-processing industry, about 680 kg of fungal biomass attributing to about 38% of extra protein could be produced for each 1 metric ton of pea-processing byproduct. This study is the first of its kind to demonstrate the potential of the pea-processing byproduct to be used by filamentous fungi to produce vegan-mycoprotein for human food applications.

Conclusion

The pea-processing byproduct (PpB) was proved to be an efficient medium for the growth of filamentous fungi to produce a vegan-protein concentrate. Moreover, an industrial scenario for the production of vegan-mycoprotein concentrate for human nutrition is proposed as an integrated process to the existing PPI production facilities.

Potato protein liquor (PPL), a side stream from the potato starch industry, is normally used as fertilizer. However, with more than 100 g/L of sugars, 20 g/L of Kjeldahl nitrogen and Chemical Oxigen Demand (COD) of 300 g/L, it represents serious environmental challenges. The use of PPL for fungal cultivation is a promising solution to convert this waste into valuable products. In this study, PPL was characterized and used to cultivate edible zygomycete Rhizopus oryzae, which is widely used in Southeast Asian cuisine to prepare e.g., tempeh. Moreover, it can be potentially used as a protein source in animal feed worldwide. Under the best conditions, 65.47 ± 2.91 g of fungal biomass per litre of PPL was obtained in airlift bioreactors. The total Kjeldahl nitrogen content of the biomass was above 70 g/kg dry biomass. The best results showed 51% reduction of COD and 98.7% reduction in the total sugar content of PPL.

The production of starch in European Union (EU 28) was around 10 million tonnes in 2013, 12.6% of them being from potato¹. During the potato processing, two main by-products which have high Biological Oxygen Demand (BOD) are formed, i.e. potato pulp (PP) and potato liquor (PL)². Proteins can be partially recovered from PL, resulting in a concentrated residual material known as potato protein liquor (PoPL)^2,3. The use of PoPL has been investigated to cultivate fungal⁴ and yeast³ biomass, and produce enzymes². However, presence of nitrogen and phosphate containing materials as well as suspended solids at high concentrations⁴ limits its application in bioprocesses. The present study was proposed to investigate the precipitation of components from PoPL by ethanol in order to get an easily fermentable solution. PoPL from Lyckeby Starch AB was mixed with different amounts of ethanol and centrifuged at 3000 g for 5 min. The liquid obtained was put under a fume hood for 48 h at room temperature for ethanol evaporation. All the samples had their volumes adjusted to the same value using distilled water. The precipitate was dried at 105 °C. All experiments were done in duplicate. The precipitation of solids improved almost 500% for a mixture of equal volumes of PoPL and ethanol compared to PoPL without ethanol addition. The protein and ash contents of the precipitate were respectively higher than 245 g/kg and 420 g/kg in all the cases, making it eligible for production of fertilizer or animal feed. Most of the analysed sugars (glucose, fructose, and sucrose) stayed in the liquid phase. Ethanol concentration in the liquid phase remained close to initial value after the 48-hour evaporation. This indicates the need for a distillation column for ethanol recovery before the remaining sugar solution can be used for fermentation purposes.