Rice in a silver spoon
doi:10.1038/nindia.2017.102 Published online 14 August 2017
Could farmers be looking at harvesting the precious metal silver alongside rice from their crop fields? Yes, if they cultivate the rice variety Garib-sal, scientists at the Indian Institute of Technology Madras (IIT-M) report1.
While screening 505 native varieties of rice for different heavy metals, the team led by chemistry professor Thalappil Pradeep noticed that nine of them were capable of absorbing silver, occurring naturally in soil. Among these, Garib-sal, a landrace from West Bengal – traditionally used by indigenous people to cure gastro-intestinal (GI) infections – was found to accumulate silver at an exceptionally high concentration: 15.61 mg/kg.
The researchers claim that this is the first investigation of the deposition of silver in rice grains.
Silver ions are known to be detrimental to pathogenic microbes. The finding also endorses the use of this rice in traditional indigenous medicine as a treatment for GI infections, the researchers say.
Accumulation of silver does not alter the grain morphology, chemical characteristics or food value of the rice. Mass spectrometry analysis showed that silver was accumulated mostly in the grain's outer layer (rice bran) removable through milling. "We suggest growing this landrace as a possible means of agricultural extraction of the noble metal from the rice bran," the scientists say.
Debal Deb, one of the authors and head of the Basudha farm, located in Odisha's Rayagada district, where the rice varieties were grown, says the discovery will be patented. "Presently Garib-sal is not very popular among farmers because it is not high yielding. But the finding that silver comes as a bonus may change that," he told Nature India.
1. Sen Gupta, S. et al. Unusual accumulation of silver in the aleurone layer of an Indian rice (Oryza sativa) landrace and sustainable extraction of the metal. ACS Sustainable Chem. Eng. (2017) doi:10.1021/acssuschemeng.7b02058