Investigating substrate possibilities regarding filamentous fungi as a food protein source

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Examensarbete för masterexamen
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2020
Författare
Latorre, Lisa
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An alternative to animal meat was found in the 1960s due an increase in the global demand for protein as the global population increased. This protein alternative, called mycoprotein, is made by filamentous fungi growing on various types of nutrients and using them as carbon sources. Generally, the environmental impact of mycoprotein is lower than that of beef and is dependent on where the carbon sources come from. The use of waste as substrate medium would further decrease environmental impact. This work, in collaboration with Mycorena AB, had the main goals to investigate if any possible improvements to their defined standard medium could be made, if side streams work as substrates and if these settings are possible at a larger scale in bioreactors compared to a laboratory setting in shake flasks. The experimental methods involved comparing dry weight of produced fungal biomass, investigating composition of the substrate media before and after cultivation, and lastly, to investigate the protein content of the fungal biomass. One fungal strain was used in this work, but there are several different fungi that can be used for mycoprotein production. The nitrogen source in the standard medium was altered from ammonium sulphate to ammonium nitrate, ammonium citrate and urea to see if production of fungal biomass could be increased. Urea seemed to be a good alternative if a switch would be made, otherwise, lowering the concentration of ammonium sulphate could be an alternative. Reducing amounts of ammonium sulphate use would reduce costs for Mycorena AB and would reduce the environmental impact of production. A change in C:N ratio regarding ammonium sulphate did not show any large differences, which further supports the conclusion that lowering the amount of ammonium sulphate could be a good alternative. Several food side- and waste streams were tried in a laboratory scale, and fungal biomass was produced in varying amounts. One dairy waste stream and oat residues were investigated further, and produced a larger amount of fungal biomass compared to the standard substrate medium. Investigations showed that the oat residue is sensitive to storage and that additions of trace minerals does not enhance production of fungal biomass, indicating that these side streams are dense in nutrients. Scale-up experiments were not conducted as desired due to complications in Mycorena AB’s production. However, data was collected from their production facility in three different cultivations. Results showed that pH is a limiting factor and that metabolite production of ethanol occurs when sugar levels are low which impairs production of fungal biomass.
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mycoprotein, side-streams, filamentous fungi, nitrogen sources, fungal biomass, oat residues, protein
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