"Bioplastics" that are naturally synthesized by microbes could be made commercially viable by using waste cooking oil as a starting material. This would reduce environmental contamination and also give high-quality plastics suitable for medical implants, according to scientists presenting their work at the Society for General Microbiology's Autumn Conference at the University of Warwick.

The Polyhydroxyalkanoate (PHA) family of polyesters is synthesized by a wide variety of bacteria as an energy source when their carbon supply is plentiful. Poly 3-hydroxybutyrate (PHB) is the most commonly produced polymer in the PHA family. Currently, growing bacteria in large fermenters to produce high quantities of this bioplastic is expensive because glucose is used as a starting material.

Work by a research team at the University of Wolverhampton suggests that using waste cooking oil as a starting material reduces production costs of the plastic. "Our bioplastic-producing bacterium, Ralstonia eutropha H16, grew much better in oil over 48 hours and consequently produced three times more PHB than when it was grown in glucose," explained Victor Irorere who carried out the research. "Electrospinning experiments, performed in collaboration with researchers from the University of Birmingham, showed that nanofibres of the plastic produced from oils were also less crystalline, which means the plastic is more suited to medical applications."

Previous research has shown that PHB is an attractive polymer for use as a microcapsule for effective drug delivery in cancer therapy and also as medical implants, due to its biodegradability and non-toxic properties. Improved quality of PHB combined with low production costs would enable it to be used more widely.

The disposal of used plastics - which are largely non-biodegradable - is a major environmental issue. Plastic waste on UK beaches has been steadily increasing over the past two decades and now accounts for about 60% of marine debris. "The use of biodegradable plastics such as PHB is encouraged to help reduce environmental contamination. Unfortunately the cost of glucose as a starting material has seriously hampered the commercialization of bioplastics," said Dr Iza Radecka who is leading the research. "Using waste cooking oil is a double benefit for the environment as it enables the production of bioplastics but also reduces environmental contamination caused by disposal of waste oil."

The next challenge for the group is to do appropriate scale-up experiments, to enable the manufacture of bioplastics on an industrial level.

More information: Dr Radecka's poster presentation "Making bioplastic from different oils" will take place on Monday 3 September at the Society for General Microbiology's Autumn Conference 2012.

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Waste cooking oil makes bioplastics cheaper

Digested coconut oil is able to attack the bacteria that cause tooth decay. It is a natural antibiotic that could be incorporated into commercial dental care products, say scientists presenting their work at the Society for General Microbiology's Autumn Conference at the University of Warwick.

The team from the Athlone Institute of Technology in Ireland tested the antibacterial action of coconut oil in its natural state and coconut oil that had been treated with enzymes, in a process similar to digestion. The oils were tested against strains of Streptococcus bacteria which are common inhabitants of the mouth. They found that enzyme-modified coconut oil strongly inhibited the growth of most strains of Streptococcus bacteria including Streptococcus mutans an acid-producing bacterium that is a major cause of tooth decay.

Many previous studies have shown that partially digested foodstuffs are active against micro-organisms. Earlier work on enzyme-modified milk showed that it was able to reduce the binding of S. mutans to tooth enamel, which prompted the group to investigate the effect of other enzyme-modified foods on bacteria.

Further work will examine how coconut oil interacts with Streptococcus bacteria at the molecular level and which other strains of harmful bacteria and yeasts it is active against. Additional testing by the group at the Athlone Institute of Technology found that enzyme-modified coconut oil was also harmful to the yeast Candida albicans that can cause thrush.

The researchers suggest that enzyme-modified coconut oil has potential as a marketable antimicrobial which could be of particular interest to the oral healthcare industry. Dr Damien Brady who is leading the research said, "Dental caries is a commonly overlooked health problem affecting 60-90% of children and the majority of adults in industrialized countries. Incorporating enzyme-modified coconut oil into dental hygiene products would be an attractive alternative to chemical additives, particularly as it works at relatively low concentrations. Also, with increasing antibiotic resistance, it is important that we turn our attention to new ways to combat microbial infection."

The work also contributes to our understanding of antibacterial activity in the human gut. "Our data suggests that products of human digestion show antimicrobial activity. This could have implications for how bacteria colonize the cells lining the digestive tract and for overall gut health," explained Dr Brady. "Our research has shown that digested milk protein not only reduced the adherence of harmful bacteria to human intestinal cells but also prevented some of them from gaining entrance into the cell. We are currently researching coconut oil and other enzyme-modified foodstuffs to identify how they interfere with the way bacteria cause illness and disease," he said.

More information: Dr Brady's poster presentation "Inhibition of cariogenic streptococci using enzyme modified coconut oil" will take place on Monday 3 September at the Society for General Microbiology's Autumn Conference 2012.

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Coconut oil could combat tooth decay