Biodegradation of Jatropha curcas phorbol esters in soil.
BACKGROUND
Jatropha curcas seed cake is generated as a by-product during biodiesel production. Seed cake containing toxic phorbol esters (PEs) is currently used as a fertiliser and thus it is of eco-toxicological concern. In the present study the fate of PEs in soil was studied.


RESULTS
Two approaches for the incorporation of PEs in soil were used. In the first, silica was bound to PEs, and in the second, seedcake was used. At day 0, the concentration of PEs in soil was 2.6 and 0.37 mg g(-1) for approach 1 and 2 respectively. PEs from silica bound PEs were completely degraded after 19, 12, 12 days (at 130 g kg(-1) moisture) and after 17, 9, 9 days (at 230 g kg(-1) moisture) at room temperature, 32 degrees C and 42 degrees C respectively. Similarly at these temperatures PEs from seed cake were degraded after 21, 17 and 17 days (at 130 g kg(-1) moisture) and after 23, 17, and 15 days (at 230 g kg(-1) moisture). Increase in temperature and moisture increased rate of PEs degradation. Using the snail (Physa fontinalis) bioassay, mortality by PE-amended soil extracts decreased with the decrease in PE concentration in soil.


CONCLUSIONS
Jatropha PEs are biodegradable. The degraded products are innocuous.
Devappa
Rakshit K
RK
Institute for Animal Production in the Tropics and Subtropics (480b), University of Hohenheim, 70593 Stuttgart, Germany.
Makkar
Harinder Ps
HP
Becker
Klaus
K
D000818:Animals; D001673:Biodegradation, Environmental; D005308:Fertilizers; D007220:Industrial Waste; D031286:Jatropha / Q000737:chemistry*; D010703:Phorbol Esters / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D012908:Snails; D012987:Soil / Q000737:chemistry*; D012989:Soil Pollutants / Q000737:chemistry*; D013696:Temperature; D014867:Water
D005308:Fertilizers; D007220:Industrial Waste; D010703:Phorbol Esters; D012987:Soil; D012989:Soil Pollutants; D014867:Water; D012822:Silicon Dioxide