Research round-up: NASA, active packaging and dormant pathogens

By Joseph James Whitworth contact

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©iStock. Let us know about your work for a chance to feature in our round-up: joe.whitworth@wrbm.com
©iStock. Let us know about your work for a chance to feature in our round-up: joe.whitworth@wrbm.com
Summer is almost over and it is back to the research lab – we take a look at what research has been done in the last month.

We start with two plant pathology professors from Penn State receiving $1.2m to study Fusarium fungi.

David Geiser and Seogchan Kang of the College of Agricultural Sciences got the grant from the National Science Foundation.

Fusarium species can cause disease in plants, animals and humans and produce toxins that contaminate food. One species may cause blight on wheat and barley while another may be used as a biological control to inhibit the growth of pathogenic microbes.

Geiser and Kang will produce a new monograph of the Fusarium genus​.

It will provide a description of all currently known species and use new and existing gene sequence data as molecular fingerprints. It also will include chapters that summarize the biological and ecological diversity of the genus.

Project participants include the USDA's Agricultural Research Service; National Agriculture and Food Research Organization in Tsukuba Science City, Ibaraki, Japan; Agriculture and Agri-Food Canada, in Ottawa and Westerdijk Fungal Biodiversity Institute in Utrecht, Netherlands.

Scientists are making strides toward the development of a protein database​ capable of identifying fish species.

Fish can be tagged with misleading names at numerous points along the journey from the docks to processing plants to retail establishments.

Antje Stahl and Uwe Schröder wanted to determine if mass spectrometry could be used to swiftly and accurately identify fish.

Researchers identified protein profiles or ‘fingerprints’ for 54 species including salmon, trout, swordfish and other fish commonly sold in grocery stores or restaurants. They confirmed these findings using DNA barcoding, a process that uses a partial DNA sequence from a mitochondrial gene.

However, in some cases, they were only able to identify a sample's genus (i.e. Thunnus) rather than the exact species.

Cold plasma fails on produce

Low-pressure cold plasma for disinfection of ISS grown produce​ was not successful with unacceptable kill rates, according to NASA research​.  

The produce was also negatively impacted by exposure to the plasma. E. coli was the challenge organism.

Since cold plasma uses no liquids it has the advantage when used in microgravity of not having to separate liquids from the item being cleaned.

Exposure times from 0 to 60 minutes and pressures ranging from 0.10 to 1.0 mbar were used to optimize plasma parameters.

Dr Xiaonan Lu, an associate professor of food science at the University of British Columbia, is leading researchers in an effort to develop an assay to detect dormant pathogens​ - referred to as viable but non-culturable (VBNC) on fresh and processed produce.

"VBNC is a relatively new concept to the fresh produce industry. There's very, very limited studies that have been done to prove VBNC is on fresh produce, so this is a pretty new topic."

Lu said growers and processors may need to rethink the types and levels of antimicrobials they use to treat water to account for VBNC pathogens.

Potential of packaging

Scientists have developed a packaging film coated with clay nanotubes​ packed with an antibacterial essential oil.

Hayriye Ünal’s team started with a polyethylene film. To scavenge for ethylene and provide a gas barrier they incorporated clay "halloysite nanotubes" which prevent oxygen from entering the film, and water vapour and other gases from escaping.

Researchers loaded the nanotubes with a natural antibacterial essential oil called carvacrol and coated the inner surface of the packaging film with the loaded nanotubes to kill microbes.

After 10 days, tomatoes wrapped with the film were better preserved than control vegetables. It also helped bananas stay more firm and keep their yellow colour after six days compared to control fruit.

Specially designed plastic films​ can prevent bacterial contamination and bacteria from forming biofilms in the food industry.

The films are modified to prevent contamination by integrating "N-halamines," special chemical groups, within the polymer matrix. N-halamines are composed of a nitrogen and a chlorine atom and sometimes other elements. They were tested using two E. coli and Listeria.

Depending on the composition, the N-halamines can kill bacteria on contact, or by releasing chlorine to kill the bacteria.

Nitin Nitin, professor and engineer, departments of Food Science and Technology and Biological and Agricultural Engineering at UC Davis, said: “Currently, we do not have an active approach to continuously prevent deposition of bacteria during food processing operations, and can only remove these deposits after processing - during a cleaning shift.”

Antibiotic resistance

A novel combination of aztreonam, amikacin and polymyxin B​ was able to kill E. coli carrying mcr-1 and ndm-5 within 24 hours and prevent regrowth, according to University of Buffalo researchers.

E. coli carrying mcr-1 and ndm-5 genes make the bacterium immune to last-resort antibiotics.

Zackery Bulman, PharmD, first author, a graduate and former postdoctoral fellow at the UB School of Pharmacy and Pharmaceutical Sciences, said only the three drugs combined worked to suppress and kill the bacteria.

We overcame the bacteria by pushing it as far as possible with an agent that it was resistant to while simultaneously administering two other antibiotics,”​ said Bulman, who is now assistant professor at the University of Illinois at Chicago College of Pharmacy.

The US Environmental Protection Agency has announced a project​ to develop methods to improve understanding of the distribution of freshwater mussels​.

EPA will partner with the West Virginia Department of Natural Resources, the Maryland Department of Natural Resources and the Pennsylvania Department of Environmental Protection.

Freshwater mussels improve water quality by filtering and sequestering pollutants and suspended particulates and removing harmful toxins and pathogens that are threats to public health.

Currently, it takes time, effort and money to assess mussel populations but it is now possible to monitor mussels by collecting water and/or sediment samples and analyze for their DNA.

This method lowers the level of effort in traditional freshwater mussel assessments and will help provide an early warning system for water quality changes and act as sensors for drinking water.

Related topics: R&D, Fresh produce, Shelf life

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