Pichia anomala as a biocontrol agent during storage of high-moisture feed grain under airtight conditions

147

This study aimed at investigating the antifungal activity of Wickerhamomyces anomalus and sourdough lactic acid bacteria to extend the shelf life of wheat flour bread. The antifungal activity was assayed by agar diffusion, growth rate inhibition, and conidial germination assays, using Penicillium roqueforti DPPMAF1 as the indicator fungus. Sourdough fermented by Lactobacillus plantarum 1A7 (S1A7) and dough fermented by W. anomalus LCF1695 (D1695) were selected and characterized. The water/salt-soluble extract of S1A7 was partially purified, and several novel antifungal peptides, encrypted into sequences of Oryza sativa proteins, were identified. The water/salt-soluble extract of D1695 contained ethanol and, especially, ethyl acetate as inhibitory compounds. As shown by growth inhibition assays, both water/salt-soluble extracts had a large inhibitory spectrum, with some differences, toward the most common fungi isolated from bakeries. Bread making at a pilot plant was carried out with S1A7, D1695, or a sourdough started with a combination of both strains (S1A7-1695). Slices of the bread manufactured with S1A7-1695 did not show contamination by fungi until 28 days of storage in polyethylene bags at room temperature, a level of protection comparable to that afforded by 0.3% (wt/wt) calcium propionate. The effect of sourdough fermentation with W. anomalus LCF1695 was also assessed based on rheology and sensory properties.The major problem for long-term shelf life of baked goods is contamination with fungi. Although they are used as the main chemical preservatives, salts of propionic, sorbic, and benzoic acids have shown several drawbacks. Reports on the appearance of cancer-like tumors in rats fed with propionic acid at concentrations of up to 4% led to prohibition of the use of calcium propionate in some European countries (31). Prolonged preservation of breads with high concentrations of calcium propionate stimulated the growth of resistant strains of Penicillium roqueforti (42). Since a few years ago, the European directive on preservatives (18) decreased the permitted concentrations of sorbate and propionate to 0.2 and 0.3% (wt/wt), respectively. Ethanol is also permitted as an antifungal preservative (2% [wt/wt]). Its inhibitory effect varies depending on the fungal species, and in some cases, it is not sufficient to prevent contamination (14).Several studies have focused on the antifungal activity of compounds from natural sources and on biopreservation as effective alternatives to chemical preservatives. Several antimicrobial compounds have been identified, especially proteins or peptides from plants, as well as metabolites derived from fermentation by lactic acid bacteria (12,23,25,42,43). Besides acidification during sourdough fermentation, lactic acid bacteria also synthesize a wide range of low-molecular-weight compounds (27), peptides (28), and proteins (10, 37) with antifungal activity. Unfortunately, only a few studies have assessed their inhibitory activity under bread-making conditions. Recent studie...

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Antifungal Activity of Wickerhamomyces anomalus and Lactobacillus plantarum during Sourdough Fermentation: Identification of Novel Compounds and Long-Term Effect during Storage of Wheat Bread

Coda

Cassone

Rizzello

et al. 2011

147

“…They found that C. infirmominiatum was the most sensitive to exogenous H 2 O 2 , while M. fructicola was the most tolerant (27,28,30 In addition to oxidative stress, antagonistic yeasts may also have to deal with the low oxygen levels associated with controlledatmosphere storage. This is especially true for the biocontrol agents used to manage mold in grain stored under airtight conditions (57). In this respect, P. anomala J121, a yeast strain used in the biocontrol of mold in grain during storage under conditions of low oxygen and high carbon dioxide, has been extensively studied.…”

Section: Environmental Stressesmentioning

confidence: 99%

Responses of Yeast Biocontrol Agents to Environmental Stress

Yuan

Wisniewski

Droby

et al. 2015

118

c Biological control of postharvest diseases, utilizing wild species and strains of antagonistic yeast species, is a research topic that has received considerable attention in the literature over the past 30 years. In principle, it represents a promising alternative to chemical fungicides for the management of postharvest decay of fruits, vegetables, and grains. A yeast-based biocontrol system is composed of a tritrophic interaction between a host (commodity), a pathogen, and a yeast species, all of which are affected by environmental factors such as temperature, pH, and UV light as well as osmotic and oxidative stresses. Additionally, during the production process, biocontrol agents encounter various severe abiotic stresses that also impact their viability. Therefore, understanding the ecological fitness of the potential yeast biocontrol agents and developing strategies to enhance their stress tolerance are essential to their efficacy and commercial application. The current review provides an overview of the responses of antagonistic yeast species to various environmental stresses, the methods that can be used to improve stress tolerance and efficacy, and the related mechanisms associated with improved stress tolerance.

“…P. anomala strain J121 can reduce the growth of P. roqueforti in vitro, in high-moisture cereal grain in a test-tube version of a malfunctioning storage system, and in 0.21-m 3 pilot scale silos for airtight storage of 160-kg batches of moist grain (3,7,(22)(23)(24). Airtight storage of cereal grain is an energy-saving alternative to hot-air drying.…”

mentioning

confidence: 99%

Nutrient Effects on Biocontrol of Penicillium roqueforti by Pichia anomala J121 during Airtight Storage of Wheat

Druvefors

Passoth

Schnürer

2005

The biocontrol yeast Pichia anomala inhibits the growth of a variety of mold species. We examined the mechanism underlying the inhibition of the grain spoilage mold Penicillium roqueforti by the biocontrol yeast P. anomala J121 during airtight storage. The biocontrol effect in a model grain silo with moist wheat (water activity of 0.96) was enhanced when complex medium, maltose, or glucose was added. Supplementation with additional nitrogen or vitamin sources did not affect the biocontrol activity of the yeast. The addition of complex medium or glucose did not significantly influence the yeast cell numbers in the silos, whether in the presence or absence of P. roqueforti. Mold growth was not influenced by the addition of nutrients, if cultivated without yeast. The products of glucose metabolism, mainly ethanol and ethyl acetate, increased after glucose addition to P. anomala-inoculated treatments. Our results suggest that neither competition for nutrients nor production of a glucose-repressible cell wall lytic enzyme is the main mode of action of biocontrol by P. anomala in this grain system. Instead, the mold-inhibiting effect probably is due to the antifungal action of metabolites, most likely a combination of ethyl acetate and ethanol, derived from glycolysis. The discovery that sugar amendments enhance the biocontrol effect of P. anomala suggests novel ways of formulating biocontrol yeasts.