CBN-V Video Archives - S2-05
Biodegradation of Cyanogens in Cassava Starch/Sago Factory Effluents by Immobilised Microorganisms

Balagopalan C., T.P. Anupama, K. Sasikiran, V.R. Bindumole and M.R. Rekha

CTCRI, PO Box 3502, Sreekariyam, Trivandrum 695017, India bal@ctcri.ren.nic.in

        Cassava starch/sago factory effluents, which have a high cyanide concentration, pose serious environmental problems and threaten quality of life. Approximately 4000-6000 litres of wastewaters are discharged to the environment for every tonne of starch/sago produced. During the process of starch extraction, large quantities of cyanogens present in cassava roots are released from the disrupted cells and become the major source of high cyanide levels in the wastewaters discharged. The total cyanogens in the waste water samples discharged from starch/sago factories ranged between 10.4 to 27.4 mg/l while the levels of total cyanogens in the ground water sources near the factories ranged between 1.3 to 1.6 mg/l. Cyanide is a metabolic inhibitor, meaning that the waste waters are a threat to the human population. Microorganisms capable of using cyanide as source of nitrogen viz. Bacillus sp., Saccharomyces sp. and Aspergillus sp. isolated from cassava starch factory effluents were immobilised in alginate beads by entrapment and on Keisulghur and brick powder by adsorption. The ability of each organism to degrade cyanide was studied at six different intervals. The percentage of reduction in the case of immobilised Bacillus cells were found to be maximum (80%) followed by Aspergillus cells (73%) and yeast cells (50%). The results obtained from the studies illustrate the potential benefits of exploring the use of immobilised microbial cells for the detoxification of cyanogens in wastewaters generated from cassava starch/sago factories. A low cost effluent treatment system could be developed to protect the environment, produce methane gas and recycle wastewater for aquaculture.

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