Indigenous butyric acid-degrading bacteria as surrogate pit latrine odour control: isolation, biodegradability performance and growth kinetics

Abstract

Butyric acid is one of the volatile organic compounds that significantly contribute to malodour emission from pit latrines. The purpose of this work is to isolate and identify bacterial strains that have the capability to degrade butyric acid, determine their butyric acid degradation efficiencies and estimate their growth pattern parameters of microbiological relevance. Pure cultures of bacterial strains capable of degrading butyric acid were isolated from pit latrine faecal sludge using an enrichment technique and were identified based on 16S rRNA analysis. The bacterial strains were cultured in mineral salt medium (MSM) supplemented with 1000 mg L −1 butyric acid, as a sole carbon and energy source, at 30 ± 1 °C, pH 7 and 110 rpm under aerobic growth conditions. The modified Gompertz model was used to estimate growth pattern parameters of microbiological relevance. Bacterial strains were phylogenetically identified as Alcaligenes sp. strain SY1, Achromobacter animicus, Pseudomonas aeruginosa, Serratia marcescens, Achromobacter xylosoxidans, Bacillus cereus, Lysinibacillus fusiformis, Bacillus methylotrophicus and Bacillus subtilis. The bacterial strains in pure cultures degraded butyric acid of 1000 mg L −1 within 20–24 h. The growth kinetics of the bacterial strains in pure culture utilising butyric acid were well described by the modified Gompertz model. This work highlights the potential for use of these bacterial strains in microbial degradation of butyric acid for deodorisation of pit latrine faecal sludge. This work also contributes significantly to our understanding of bioremediation of faecal sludge odours and informs the development of appropriate odour control technologies that may improve odour emissions from pit latrines.