A Solvent-Free Approach for Converting Cellulose Waste into Volatile Organic Compounds with Endophytic Fungi.

Simple sugars produced from a solvent-free mechanocatalytic degradation of cellulose were evaluated for suitability as a growth medium carbon source for fungi that produce volatile organic compounds. An endophytic Hypoxylon sp. (CI-4) known to produce volatiles having potential value as fuels was initially evaluated. The growth was obtained on a medium containing the degraded cellulose as the sole carbon source, and the volatile compounds produced were largely the same as those produced from a conventional dextrose/starch diet. A second Hypoxylon sp. (BS15) was also characterized and shown to be phylogenetically divergent from any other named species. The degraded cellulose medium supported the growth of BS15, and approximately the same quantity of the volatile compounds was produced as from conventional diets. Although the major products from BS15 grown on the degraded cellulose were identical to those from dextrose, the minor products differed. Neither CI-4 or BS15 exhibited growth on cellulose that had not been degraded. The extraction of volatiles from the growth media was achieved using solid-phase extraction in order to reduce the solvent waste and more efficiently retain compounds having low vapor pressures. A comparison to more conventional liquid⁻liquid extraction demonstrated that, for CI-4, both methods gave similar results. The solid-phase extraction of BS15 retained a significantly larger variety of the volatile compounds than did the liquid⁻liquid extraction. These advances position the coupling of solvent-free cellulose conversion and endophyte metabolism as a viable strategy for the production of important hydrocarbons.

Pushing the limits of mercury sensors with gold nanorods.

The method presented here provides a direct way to determine mercury in tap water samples at the parts-per-trillion level. Its outstanding selectivity and sensitivity results from the well-known amalgamation process that occurs between mercury and gold. The entire procedure takes less than 10 min. No sample separation or sample preconcentration is required. The only step prior to mercury determination consists of mixing the water sample with a gold nanorod solution in sodium borohydride. The analytical figures of merit demonstrate precise and accurate analysis at the parts-per-trillion level. The limit of detection (6.6 x 10(-13) g x L(-1)) shows excellent potential for monitoring ultralow levels of mercury in water samples.