NSC unveils 'bio' PHBV plastic

The National Science Council (NSC) yesterday presented a patented and innovative process for making polyhydroxybutyrate-valerate (PHBV), a biodegradable plastic made from the bacterial fermentation of starch.

"In a time when fossil fuels are increasingly scarce and expensive, our breakthrough allows us to cost-efficiently mass produce greener [more environmentally friendly] plastics," research coordinator Don Trong-ming (董崇民), a professor at the department of chemical and materials engineering at Tamkang University, told a press conference.

"Not only can PHBV be made into consumer products, its bio-compatibility allows for the production of biomedical products such as sutures and bone plates," he said.

The six-year research project was an interdisciplinary effort involving six universities, NSC Deputy Minister Yang Hung-tun (楊弘敦) said.

PHBV is a type of polyhydroxyalkanoate (PHA), a substance produced by microorganisms as a nutrient-conserving mechanism when nitrogen, phosphorus and sulfur are scarce, Don said.

"Basically, PHA plastics are made by microorganisms and microorganisms can degrade them," Don said, adding that in compost PHA can completely biodegenerate into water and carbon dioxide in just three months.

"PHA was named by Forbes magazine in 2003 as one of the five molecules that will change the world; molecules that can incur substantial profits on their advances on the molecular level," he said.

The most common type of PHA is poly-beta-hydroxybutyrate (PHB), a compound similar to polypropylene but stiffer and more brittle, Don said, adding that PHB is also limited in application because of its cost and small temperature window for molding.

"The goal of our project was therefore to combat the limitations and produce a cheap, stretchy and easily moldable plastic," Don said.

"We decided to use Haloferax mediterranei, a bacteria found in the ocean, because it economically feeds on starch [rice bran and soy milk] and lives in highly saturated saltwater where most other bacteria cannot survive, so the probability of contamination is low," Don said.

The team set about making the bacteria produce PHBV, a PHB copolymer that has a valerate component attached to the PHB compound, which makes the plastic more stretchy, said Simon Lai (賴森茂), a professor at National Ilan University.

"The breakthrough came when we developed a two-staged fermentation process to force the bacteria to produces PHBV in the second stage, instead of PHB, because of a diet change," Don said.

"Our PHBV yield of 55.6 percent is much higher than market standards," said Will Chen, (陳志成), chairman of the department of biomedical engineering at Tatung University. "And while many current biodegradable plastic productions depend on genetic manipulation and cost up to US$8 to US$10 per kilogram, ours cost between US$3.74 and US$4.79."

"In the future we aim to make the plastic even greener by utilizing food waste as feedstock," Don said.

Talks with businesses for market production have been initiated, Don said, adding that, "we hope the mass production of this green plastic will help alleviate the environmental burden that traditional plastic brings."