ABSTRACT
HISTORY OF FUNGAL PROTEIN FOR FOOD Fungi have been part of the human diet for thousands of years as a food item in itself — especially mushrooms — or as part of fermented foods like yeasts used in bread and beverages. Other well-known fermented products using filamentous fungi are blue and white moulded cheeses, tempe and miso. In the late 1950s searches for new protein sources were initiated as it was estimated that animal protein sources would be insufficient to meet man’s requirements for protein. Microbial produced protein, also named single-cell protein (SCP), was in focus and many different microbial sources were investigated, mainly intended for animal feed (Spicer, 1971). Reviews on alternative protein sources and SCP from many different organisms, e.g., bacteria, fungi and algae, have been published elsewhere (Das and Singh, 2004; Özyurt and Deveci, 2004; Sadler, 2004; Villas-Boas et al., 2002). As fungi have a long history of safe use in food and food production, it has been a strategy to use these organisms, especially filamentous fungi, for production of microbial protein for human consumption. Examples on fungal species and some yeasts which have been tested for SCP production intended for food or feed are listed in Table 1. A general concern on microbial protein from a filamentous fungus, generically named mycoprotein, is the possible contamination of mycotoxins produced by the fungus, as known from food spoilage by fungi (Filtenborg et al., 1996) and from production of enzymes and
other food ingredients (Blumenthal, 2004; Mapari et al., 2005). With this in mind, it is alarming that Aspergillus fumigatus known as a highly toxigenic and even pathogenic fungus ever has been suggested as a mycoprotein producer (Table 1). The A. fumigatus mycoprotein was evaluated as safe in a rat feeding experiment (Khor et al., 1977) and also analysed for aflatoxins, citrinin, ochratoxin, zearalenone, T-2 toxin and sterigmatocystin (Reade and Gregory, 1975). These mycotoxins are not among the toxins known from A. fumigatus, and the analyses were negative as well. There have been no further reports on the use of A. fumigatus mycoprotein since the abovementioned reports from the late 1970s. One of the major work horses in biotechnology is Aspergillus niger and its use has been evaluated as safe taking into account that ochratoxin A is produced by industrial strains under laboratory conditions (Schuster et al., 2002). During the experimental SCP productions by A. niger (Table 1) a possible mycotoxin contamination was never discussed, but despite the wide use of A. niger in biotechnology, mycoprotein from this species has never been commercialised. Geotrichum candidum is widely used as starter culture in dairy industry for cheese production, but the mycoprotein production (Table 1) has been evaluated to be of less commercial value compared to SCP from Saccharomyces cerevisiae and Candida species (Table 1) due to their much higher protein per dry weight content (Ziino et al., 1999).
