Arbuscular mycorrhizas accelerate the degradation of colour containing organic pollutants present in distillery spent wash leachates

Distillery spent wash (DSW) from molasses-based distilleries is being used as a low-cost alternative to chemical fertilizers in countries like India and Brazil. However, using DSW as a fertilizer substitute causes organic pollutant leaching, including melanoidins and caramel colourants that turn bodies of water dark brown. This study investigated the arbuscular mycorrhiza (AM) mediated degradation of organic pollutants in DSW.

Mycorrhizal and non-mycorrhizal Sorghum bicolor were grown in microcosms for 16 weeks. The plants were fertilized with either raw DSW or Hoagland solution. Leachates draining from the microcosms after fertilization were collected three times in 30-day intervals. Each 30-day collection was preceded by two fertilizations. A gas chromatography-mass spectrometry comparative analyses of raw DSW with leachates of the third collection from mycorrhizal and non-mycorrhizal microcosms was made. Sixty-five and 42 complex organic compounds were detected in raw DSW and leachate collected from the non-mycorrhizal pots respectively. Only 26 compounds were detected in leachate collected from mycorrhizal pots. Absent from leachate of the mycorrhizal pots were: colour-containing organic compounds diacetone alcohol; 3-amino-2-cyano-6-methyl-6,7-dihydrothieno[2,3-b]pyrazine S-oxide; cyclohexane; 1,2-benzenedicarboxylic acid, butyl 8-methylnonyl ester; 2-pyrrolidinone; and acetic acid, dodecyl ester present in raw DSW. The results indicate that AM fungi can degrade organic pollutants in DSW.