Microbe-Mediated Control of Mycotoxigenic Grain Fungi in Stored Rice with Focus on Aflatoxin Biodegradation and Biosynthesis Inhibition

( Mohamed Mannaa ),( Ki Deok Kim ) 한국균학회 2016 Mycobiology Vol.44 No.2

Rice contaminated with fungal species during storage is not only of poor quality and low economic value, but may also have harmful effects on human and animal health. The predominant fungal species isolated from rice grains during storage belong to the genera Aspergillus and Penicillium. Some of these fungal species produce mycotoxins; they are responsible for adverse health effects in humans and animals, particularly Aspergillus flavus, which produces the extremely carcinogenic aflatoxins. Not surprisingly, there have been numerous attempts to devise safety procedure for the control of such harmful fungi and production of mycotoxins, including aflatoxins. This review provides information about fungal and mycotoxin contamination of stored rice grains, and microbe-based (biological) strategies to control grain fungi and mycotoxins. The latter will include information regarding attempts undertaken for mycotoxin (especially aflatoxin) bio-detoxification and microbial interference with the aflatoxin-biosynthetic pathway in the toxin-producing fungi.

Biocontrol Activity of Volatile-Producing Bacillus megaterium and Pseudomonas protegens Against Aspergillus and Penicillium spp. Predominant in Stored Rice Grains: Study II

( Mohamed Mannaa ),( Ki Deok Kim ) 한국균학회 2018 Mycobiology Vol.46 No.1

In our previous studies, Bacillus megaterium KU143, Microbacterium testaceum KU313, and Pseudomonas protegens AS15 have been shown to be antagonistic to Aspergillus flavus in stored rice grains. In this study, the biocontrol activities of these strains were evaluated against Aspergillus candidus, Aspergillus fumigatus, Penicillium fellutanum, and Penicillium islandicum, which are predominant in stored rice grains. In vitro and in vivo antifungal activities of the bacterial strains were evaluated against the fungi on media and rice grains, respectively. The antifungal activities of the volatiles produced by the strains against fungal development and population were also tested using I-plates. In in vitro tests, the strains produced secondary metabolites capable of reducing conidial germination, germ-tube elongation, and mycelial growth of all the tested fungi. In in vivo tests, the strains significantly inhibited the fungal growth in rice grains. Additionally, in I-plate tests, strains KU143 and AS15 produced volatiles that significantly inhibited not only mycelial growth, sporulation, and conidial germination of the fungi on media but also fungal populations on rice grains. GC-MS analysis of the volatiles by strains KU143 and AS15 identified 12 and 17 compounds, respectively. Among these, the antifungal compound, 5-methyl-2-phenyl-1H-indole, was produced by strain KU143 and the antimicrobial compounds, 2-butyl 1-octanal, dimethyl disulfide, 2-isopropyl- 5-methyl-1-heptanol, and 4-trifluoroacetoxyhexadecane, were produced by strain AS15. These results suggest that the tested strains producing extracellular metabolites and/or volatiles may have a broad spectrum of antifungal activities against the grain fungi. In particular, B. megaterium KU143 and P. protegens AS15 may be potential biocontrol agents against Aspergillus and Penicillium spp. during rice grain storage.

Biocontrol Activity of Volatile-Producing Bacillus megaterium and Pseudomonas protegens against Aspergillus flavus and Aflatoxin Production on Stored Rice Grains

( Mohamed Mannaa ),( Ji Yeon Oh ),( Ki Deok Kim ) 한국균학회 2017 Mycobiology Vol.45 No.3

In our previous study, three bacterial strains, Bacillus megaterium KU143, Microbacterium testaceum KU313, and Pseudomonas protegens AS15, were selected as effective biocontrol agents against Aspergillus flavus on stored rice grains. In this study, we evaluated the inhibitory effects of the volatiles produced by the strains on A. flavus growth and aflatoxin production on stored rice grains. The three strains significantly reduced mycelial growth of A. flavus in dual-culture assays compared with the negative control strain, Sphingomonas aquatilis KU408, and an untreated control. Of these tested strains, volatiles produced by B. megaterium KU143 and P. protegens AS15 markedly inhibited mycelial growth, sporulation, and conidial germination of A. flavus on agar medium and suppressed the fungal populations in rice grains. Moreover, volatiles produced by these two strains significantly reduced aflatoxin production in the rice grains by A. flavus. To our knowledge, this is the first report of the suppression of A. flavus aflatoxin production in rice grains using B. megaterium and P. protegens volatiles.

Effect of Temperature and Relative Humidity on Growth of Aspergillus and Penicillium spp. and Biocontrol Activity of Pseudomonas protegens AS15 against Aflatoxigenic Aspergillus flavus in Stored Rice Grains

( Mohamed Mannaa ),( Ki Deok Kim ) 한국균학회 2018 Mycobiology Vol.46 No.3

In this study, we evaluated the effect of different temperatures (10, 20, 30, and 40℃) and relative humidities (RHs; 12, 44, 76, and 98%) on populations of predominant grain fungi (Aspergillus candidus, Aspergillus flavus, Aspergillus fumigatus, Penicillium fellutanum, and Penicillium islandicum) and the biocontrol activity of Pseudomonas protegens AS15 against aflatoxigenic A. flavus KCCM 60330 in stored rice. Populations of all the tested fungi in inoculated rice grains were significantly enhanced by both increased temperature and RH. Multiple linear regression analysis revealed that one unit increase of temperature resulted in greater effects than that of RH on fungal populations. When rice grains were treated with P. protegens AS15 prior to inoculation with A. flavus KCCM 60330, fungal populations and aflatoxin production in the inoculated grains were significantly reduced compared with the grains untreated with strain AS15 regardless of temperature and RH (except 12% RH for fungal population). In addition, bacterial populations in grains were significantly enhanced with increasing temperature and RH, regardless of bacterial treatment. Higher bacterial populations were detected in biocontrol strain-treated grains than in untreated control grains. To our knowledge, this is the first report showing consistent biocontrol activity of P. protegens against A. flavus population and aflatoxin production in stored rice grains under various environmental conditions of temperature and RH.

Halal Tourism inUnited Arab Emirates

Maryam Mannaa 한국문화관광학회 2020 문화관광연구 Vol.22 No.1

The halal or Muslims’ travel segment is recognized as a powerful commercial force and is one of the fastest growing segments in the international tourism industry. In 2017, the number of Muslim visitor arrivals was estimated at 131 million globally. In 2016, the share of Muslim tourists in global tourism income was evaluated at $US 155 billion. In order to take the high share from this emerging market, different Muslim-majority and even Muslim-minority countries are taking measures to attract the greatest number of Muslim tourists. During the past five years, United Arab Emirates (UAE) was ranked amongst the top destinations for halal tourism according to the Global Muslim Travel Index (GMTI). This paper examines the different elements that have qualified UAE, particularly Dubai, to deserve this rank as a favorite destination for Muslim tourists.

Influence of Temperature and Water Activity on Deleterious Fungi and Mycotoxin Production during Grain Storage

( Mohamed Mannaa ),( Ki Deok Kim ) 한국균학회 2017 Mycobiology Vol.45 No.4

Cereal grains are the most important food source for humans. As the global population continues to grow exponentially, the need for the enhanced yield and minimal loss of agricultural crops, mainly cereal grains, is increasing. In general, harvested grains are stored for specific time periods to guarantee their continuous supply throughout the year. During storage, economic losses due to reduction in quality and quantity of grains can become very significant. Grain loss is usually the result of its deterioration due to fungal contamination that can occur from preharvest to postharvest stages. The deleterious fungi can be classified based on predominance at different stages of crop growth and harvest that are affected by environmental factors such as water activity (a_w) and eco-physiological requirements. These fungi include species such as those belonging to the genera Aspergillus and Penicillium that can produce mycotoxins harmful to animals and humans. The grain type and condition, environment, and biological factors can also influence the occurrence and predominance of mycotoxigenic fungi in stored grains. The main environmental factors influencing grain fungi and mycotoxins are temperature and a_w. This review discusses the effects of temperature and a_w on fungal growth and mycotoxin production in stored grains. The focus is on the occurrence and optimum and minimum growth requirements for grain fungi and mycotoxin production. The environmental influence on aflatoxin production and hypothesized mechanisms of its molecular suppression in response to environmental changes are also discussed. In addition, the use of controlled or modified atmosphere as an environmentally safe alternative to harmful agricultural chemicals is discussed and recommended future research issues are highlighted.

Does Food Really Matter While Travelling? The Availability of Halal Food and It’s Effect on Muslim Travellers’ Destination Selection, Destination Satisfaction and Retention: Applied Study on UAE Travellers

Maryam Taha Mannaa 세계문화관광학회 2017 International Journal of Culture and tourism Resea Vol.10 No.1

Despite the fact that Halal tourism market is booming, Muslim tourists have difficulties obtaining Halal food in many tourist destinations. Several studies indicate that Halal food is by far the most crucial requirement that a Muslim traveller seeks when traveling. However, research into the significance attached to halal food by Muslim tourists is limited. A self-administered semi-structured interview was developed. A convenience sample of UAE citizens were interviewed to test the effect of the availability of Halal food in the destination on their preference and selection of the destination, their overall satisfaction and their intensions to revisit the destination.

곡류작물의 수확전후에 발생하는 유해 저장 곰팡이와 균독소에 대한 제어 전략

모하메드 만나(Mohamed Mannaa),김기덕(Ki Deok Kim) 고려대학교 생명자원연구소 2017 생명자원연구 Vol.25 No.1

Abstract Consumption of cereals contaminated with mycotoxigenic fungi is a very serious issue threatening human and animal health. Therefore, the management of the occurrence of such fungi and control of mycotoxin level in cereals are current issues of great significance. These fungi may contaminate the grains and produce mycotoxins in cereal crops during preharvest or at postharvest periods, depending on the prevailing environmental conditions. Thus, efficient mycotoxin control strategies should consider all the factors that contribute to the accumulation of mycotoxins at different stages of the crops and adopt the most suitable control measures in an integrated control strategy. Several control measures have been proposed for the management of grain fungi and mycotoxins in the field during preharvest and at postharvest periods. Such methods include the selection of varieties resistant to the mycotoxigenic fungi, adhering to the proper cultural practices in the field, avoiding kernel damage during the harvesting process, and following the recommended postharvest practices to minimize the presence of mycotoxins in the grains. In the present review, the methods proposed for controlling mycotoxins are discussed, including the use of chemical methods, which are being replaced by other promising environment-friendly methods, such as the use of plant extracts and biocontrol microbial agents. In addition, the various antagonistic microbes as potential biocontrol agents against mycotoxigenic fungi and mycotoxins from previous studies are discussed. Finally, recommendations for future studies are provided, highlighting the importance of the integration of different control practices to minimize mycotoxins in grains and to reduce the use of synthetic chemicals.

Versatile Roles of Microbes and Small RNAs in Rice and Planthopper Interactions

Abdelaziz Mansour,Mannaa Mohamed Ibrahim Mohamed Ahmed,Omar Hewedy,Mostafa G. Ali,정혜정,서영수 한국식물병리학회 2022 Plant Pathology Journal Vol.38 No.5

Planthopper infestation in rice causes direct and indirect damage through feeding and viral transmission. Host microbes and small RNAs (sRNAs) play essential roles in regulating biological processes, such as metabolism, development, immunity, and stress responses in eukaryotic organisms, including plants and insects. Recently, advanced metagenomic approaches have facilitated investigations on microbial diversity and its function in insects and plants, highlighting the significance of microbiota in sustaining host life and regulating their interactions with the environment. Recent research has also suggested significant roles for sRNA-regulated genes during rice–planthopper interactions. The response and behavior of the rice plant to planthopper feeding are determined by changes in the host transcriptome, which might be regulated by sRNAs. In addition, the roles of microbial symbionts and sRNAs in the host response to viral infection are complex and involve defense-related changes in the host transcriptomic profile. This review reviews the structure and potential functions of microbes and sRNAs in rice and the associated planthopper species. In addition, the involvement of the microbiota and sRNAs in the rice–planthopper–virus interactions during planthopper infestation and viral infection are discussed.

Stress Tolerance and Virulence-Related Roles of Lipopolysaccharide in Burkholderia glumae

Lee, Chaeyeong,Mannaa, Mohamed,Kim, Namgyu,Kim, Juyun,Choi, Yeounju,Kim, Soo Hyun,Jung, Boknam,Lee, Hyun-Hee,Lee, Jungkwan,Seo, Young-Su The Korean Society of Plant Pathology 2019 Plant Pathology Journal Vol.35 No.5

The lipopolysaccharide (LPS) composed of lipid A, core, and O-antigen is the fundamental constituent of the outer membrane in gram-negative bacteria. This study was conducted to investigate the roles of LPS in Burkholderia glumae, the phytopathogen causing bacterial panicle blight and seedling rot in rice. To study the roles of the core oligosaccharide (OS) and the O-antigen region, mutant strains targeting the waaC and the wbiFGHI genes were generated. The LPS profile was greatly affected by disruption of the waaC gene and slight reductions were observed in the O-antigen region following wbiFGHI deletions. The results indicated that disruption in the core OS biosynthesis-related gene, waaC, was associated with increased sensitivity to environmental stress conditions including acidic, osmotic, saline, and detergent stress, and to polymyxin B. Moreover, significant impairment in the swimming and swarming motility and attenuation of bacterial virulence to rice were also observed in the waaC-defective mutant. The motility and virulence of O-antigen mutants defective in any gene of the wbiFGHI operon, were not significantly different from the wild-type except in slight decrease in swimming and swarming motility with wbiH deletion. Altogether, the results of present study indicated that the LPS, particularly the core OS region, is required for tolerance to environmental stress and full virulence in B. glumae. To our knowledge, this is the first functional study of LPS in a plant pathogenic Burkholderia sp. and presents a step forward toward full understanding of B. glumae pathogenesis.