ChemWeb Newsletter

Not a subscriber? Join now.February 28, 2006


Soil-eating microbes could change their diet to plastics, The Alchemist discovers in this week's issue. Also, we learn that polymers could be used to store hydrogen in the fuel cell cars of the future, the problem of benzene in soda, and we hear of a theoretical demonstration showing communication between quantum dots. Finally, there is international outrage over a US visa refusal for an eminent Indian chemist.

Irish and German researchers have discovered that the soil bacterium Pseudomonas putida can eat pyrolyzed oil from waste polystyrene to produce the biodegradable polymers PHA (polyhydroxyalkanoates). Kevin O'Connor of University College Dublin and colleagues there and in Germany have demonstrated that an engineered microbial strain can convert petroleum-based plastic waste into a reusable biodegradable form. O'Connor suggests that a similar process might be used to convert other types of discarded plastics into PHA. PHA is commonly used in medical materials and devices and for making plastic kitchenware, packaging film and other disposable items. It is resistant to hot liquids, greases and oils, but unlike polystyrene, it readily breaks down in soil, water, septic systems and backyard composts.

Neil McKeown of Cardiff University, UK, and collaborators Peter Budd of the University of Manchester, and David Book of the University of Birmingham have devised a new approach to hydrogen storage based on porous organic polymers that can adsorb appreciable quantities of the gas. Materials scientists are keen to find materials that can adsorb large quantities of hydrogen and other energy-rich gases for use as compact fuel supplies for fuel cells. Zeolites and activated carbons have been the focus of much of this research but cost and weight remain obstacles to their implementation in commercially viable systems. McKeown's porous polymers should be inexpensive to mass produce. The researchers suggest that by 2010 they will have succeeded in optimizing their polymers to store 6% by weight of hydrogen.

The US FDA and national food agencies around the globe are reinvestigating the safety of the food and drinks preservative sodium benzoate after a fifteen year hiatus. Soluble benzoates are converted into an antimicrobial form, benzoic acid, in acid conditions and as such are used as preservatives in soft drinks and various foodstuffs. The FDA warned, however, in the early 1990s, that this compound could degrade to benzene through interaction with hydroxyl radicals released by ascorbic or citric acids also present in some food and drink products. An early workaround involved not using ascorbic or citric acid in drinks with benzoates and not using benzoates in foods in which these acids are naturally present. Unfortunately, dozens of current manufacturers were seemingly unaware of the problem and food agencies have been finding benzene levels in soft drinks well above World Health Organization acceptable limits. Agencies are hoping to resolve the issue in order to avoid public concern frothing over.

Nanoscientists have found a way to make quantum dots, the building blocks of a future generation of computational devices, talk to each other. Ameenah Al-Ahmadi of Ohio University and colleagues built a theoretical model to study how light hitting a quantum dot might prompt a transfer of energy in a "coherent" fashion. The researchers found that when the dots were arranged further apart than the radius of the individual dots, light waves traveled between the dots in a consistent pattern. The researchers suggest this means a way to transmit information through a network of quantum dots using light might be possible. The study lays the groundwork for optical quantum computing in which photons replace electrons as the currency of information. "The idea is to make the (computing) process faster and smaller," explains Al-Ahmadi.

Eminent organic chemist Goverdhan Mehta was recently refused entry to the USA two weeks because his chemical expertise was deemed a threat to US security. The refusal to grant Mehta a US visa comes at the most inopportune time diplomatically speaking, given President Bush's imminent visit to India. Mehta is on record as being humiliated, accused of "hiding things" and being dishonest, and told that his work is dangerous because of its potential applications in chemical warfare, the Washington Post reports. Needless to say, the debacle has also caused major embarrassment to Mehta's American scientific colleagues. The consulate told Mehta "you have been denied a visa" and invited him to submit additional information, according to an official at the National Academy of Sciences who saw a copy of the document. Ironically, Mehta is president of the International Council for Science, an organization based in Paris whose aim is to facilitate collaboration between scientists internationally. The ICSU says Mehta is not alone and countless less well-known scientists are being refused US entry needlessly.