Biodegradation of free cyanide using Bacillus sp. consortium dominated by Bacillus safensis, lichenformis and tequilensis strains: A bioprocess supported solely with whey

Abstract

Several bacterial species (n=13) were isolated from electroplating wastewater to assess their ability to biodegrade free cyanide (F-CN). A mixed culture mainly dominated by Bacillus sp (Bacillus safensis, Bacillus lichenformis and Bacillus tequilensis) was cultured in nutrient broth for 48 hours at 37°C, to which F-CN as KCN (200 to 400 mg CN-/L) was added in order to evaluate the species ability to tolerate and biodegrade the cyanide. In nutrient broth, the microorganisms were able to degrade 131(65.5%) and 177 (44.3%) mg CN-/L in cultures containing 200 and 400 mg CN-/L over a period of 8 days, respectively. Subsequently, cultures were supplemented solely with agrowaste extracts, i.e. Ananas comosus extract (1% v/v), Beta vulgaris extract (1% v/v), Ipomea batatas extract (1% v/v), spent brewer’s yeast (1% v/v) and whey (0.5% w/v), as the primary carbon sources in 200 and 400 mg CN-/L cultures. The bacterial species were able to degrade F-CN in cultures that were supplemented with whey, whereby 179 (89.5%) and 239 (59.75%) mg CN-/L was biodegraded from 200 and 400 mg CN-/L cultures, respectively.