Growth Inhibition of Various Enterobacteriaceae Species by the Yeast Hansenula anomala during Storage of Moist Cereal Grain

Abstract

Eleven of 13 Enterobacteriaceae species tested grew in moist stored wheat, highlighting a potential risk of this energy-saving airtight storage method. When Hansenula anomala was coinoculated, all Enterobacteriaceae species were significantly inhibited after 2 months of storage, six of them to below the detection limit. Enterobacteriaceae species can be associated with severe human health problems, as demonstrated during the outbreak of a life-threatening hemolytic syndrome in May-June 2011 in Europe. During this outbreak, an enterohemorrhagic Escherichia coli (EHEC) strain grown on products of organic farming caused an epidemic with over 2,000 registered cases and more than 30 deaths (www.rki.de). Thus, there is pressure to minimize the number of Enterobacteriaceae organisms in the food chain; reducing the number of these bacteria in feed production has been shown to reduce their frequency in the food chain (1). Treatment of the above-mentioned EHEC strain with antibiotics increased toxin production, also indicating a demand for alternative antibacterial agents.Cereal grain is a major resource for human nutrition, animal feed, and biofuel production. Diminishing postharvest losses and ensuring the hygienic quality of cereal grain are thus central issues in generating sustainable food, feed, and bioenergy production. The most efficient method for conserving cereal grain is drying. However, this method consumes much energy-in regions with a temperate climate, such as Sweden, it is responsible for up to 60% of the total energy consumption during grain production. Moreover, even dried material retains certain risks for contamination if drying is uneven or if the material absorbs moisture from humidity in the air. Airtight storage of moist grain is an energy-saving alternative that utilizes approximately 2% of the energy of hightemperature drying (16,22). Airtight storage of moist grain is appropriate mainly for storage of animal feed, and it has been shown that the nutritional characteristics of the grain improve during storage (14). Furthermore, bioethanol production from moist stored grain was also improved, due to better accessibility of the starch for enzymatic pretreatment (18). Members of the Enterobacteriaceae have usually not been regarded as a problem in cereal grain. However, our results recently demonstrated that at least two identified Enterobacteriaceae species, E. coli and Pantoea agglomerans, can be present and grow on stored cereal grain, even at a moisture content of only 14% (14, 17). The question remains as to whether other species can also grow under these conditions. It has been shown that the biopreservation yeast Hansenula anomala can prevent mold growth in moist cereal grain (19). (There is currently a debate about the correct designation of this yeast species. The name Pichia anomala, used in recent years, does not reflect the phylogeny of this species. A new species name, Wickerhamomyces anomalus, has been proposed [9, 10], but some argue to reinstate the former name, H. anomala [20].) Int...

Nutritional, Microbial, and Allergenic Changes during the Fermentation of Cashew ‘Cheese’ Product Using a Quinoa-Based Rejuvelac Starter Culture

“…Lactococcus was present because it is also capable of lactic acid fermentation, thereby contributing to the acidity of the final product, similar to Weissella and Pediococcus [1]. The rejuvelac used for both 'brie' and 'blue' products had Enterobacteriaceae present at low levels, which may be attributed to contaminated quinoa because Enterobacteriaceae have been found to be present in cereal grains and are also common contaminants of food in general [26][27][28]. Although Enterobacteriaceae were initially present in the rejuvelac, by the end of cashew fermentation it was no longer detectable.…”

Using Candida oleophila as a biocontriol agens to prevent foodborne Escherichia coli O157 EHEC infections

“…Cryptococcus laurentii , Pichia guilliermondi , Kloeckera apiculata , Sporobolomyces roseus , Candida sake and Candida oleophila (Usall et al 20002001; Abadias et al 2001; Gamagae and Sivakumar 2004; Lassois et al 2008) have shown biocontrol effectiveness against postharvest diseases caused by fungal pathogens of apple. Recently, inhibition of E. coli and other enterobacteria by Pichia anomala and Hansenula anomala yeast in storage systems has been shown by M. Olstorpe and colleagues (Olstorpe et al, 20102012). There is few scientific literature about application of C. oleophila yeast as antagonist for controlling of EHEC O157 in vegetable or fruit products.…”

Combined moist airtight storage and feed fermentation of barley by the yeast Wickerhamomyces anomalus and a lactic acid bacteria consortium

“…Preservation is based on metabolic activities of naturally occurring microbes, mainly yeasts and lactic acid bacteria (LAB), which remove easily available nutrients, replace oxygen with CO 2 , lower the pH and produce anti-microbial metabolites(Ström et al, 2002 ; Magnusson et al, 2003 ; Olstorpe and Passoth, 2011 ). The yeast Wickerhamomyces anomalus , a biocontrol yeast naturally occurring on cereal grain has been shown to efficiently inhibit non-desirable organisms such as molds and Enterobacteriaceae in airtight storage systems (Olstorpe et al, 2010b , 2012 ).…”

“…Enterobacteriaceae have usually not been considered a problem in dried cereal grain, as they are supposedly inhibited at low water activities (Asperger and Winterer, 1978 ). However, we have recently shown that species of Enterobacteriaceae can grow on cereal grains with a moisture content of only 14% (Olstorpe et al, 2010b , 2012 ). Similarly, fermentation of liquid feed is a variable process that does not yield a predictable content of organic acids, thereby generating feed products that may in some cases not be safe or palatable (Beal et al, 2005 ).…”

“…The yeast, W. anomalus , is a promising candidate organism for such an approach. It shows considerable biocontrol activity against both molds and Enterobacteriaceae in airtight storage systems from laboratory to farm-scale (Petersson and Schnürer, 1998 ; Olstorpe et al, 2010b , 2012 ), and has previously been isolated from fermented pig feed (Olstorpe et al, 2008 ). LAB such as Lactobacillus plantarum or Pediococcus spp.…”