Abstract
The indiscriminate discharge of Cassava mill effluent pose serious environmental and public health implications. This work was aimed at assessing the biodegradation potentials of indigenous microbial isolates from cassava mill effluent using screening and shake flask degradation tests. The mean heterotrophic bacterial and fungal counts were 3.4±0.26 x 106cfu/ml and 1.1±0.20 x 106cfu/ml respectively. The microorganisms isolated, characterized and identified include the genus Pseudomonas (15.48%), Bacillus (12.41%), Acetobacter and Rhizopus (10.88%), Corynebacterium (9.33%), Lactobacillus, Micrococcus and Aspergillus (7.79%), Staphylococcus and Penicillium (6.25%) and Saccharomyces species (4.62%). The pH (5.39 ± 0.14), electrical conductivity (2506.90 ± 45.35), sulphate (210.87 ± 5.31), nitrate (365.28 ± 3.61), phosphate (107.70 ± 2.10), cyanide (19.93 ± 0.25), chemical oxygen demand (1728.33 ± 19.66), biological oxygen demand (1141.51 ± 12.69), iron (206.43±2.05), zinc (54.56 ± 0.62), manganese (19.96 ± 0.35), copper (10.67 ± 0.10) and nickel (3.28 ± 0.46) in mg/l were above the Federal Environmental Protection Agency standard for effluent discharge. Bacillus, Pseudomonas, Aspergillus and Penicillium species which had the highest turbidity were used for bioremediation studies. The consortium of microorganisms demonstrated the highest efficacy. Bioremediation of cassava mill effluent by these microorganisms was manifested in the reduction of biological oxygen demand (consortium of Pseudomonas and Bacillus species 97.42%), (Aspergillus and Penicillium species 75.32%) and chemical oxygen demand (Pseudomonas and Bacillus species 37.63%), (Aspergillus and Penicillium species 44.97%). The study has shown that microbial isolates have the potentials of reducing pollution effect thereby enhancing management of cassava mill effluent before eventual discharge into the environment.Keywords: Biodegradation, Environmental management, Microorganisms, Turbidity, Cassava mill effluent, Ebelle.
Highlights
Cassava mill effluents are produced from various stages involved in processing of Cassava tubers like washing, grating and moisture extraction processes
Collection of cassava mill effluent sample: Cassava mill effluents were collected from FADAMA (III) cassava processing mill site at Ebelle, Edo state
Bacterial and fungal isolates were screened for their utilization of cassava mill effluent using a Mineral Salt Medium (MSM)
Summary
Description of the Studied Area: Ebelle is situated in Igueben Local Government Area of Edo State, with geographical coordinates 6° 30' 0" North, 6° 12' 0" East. Enumeration of total heterotrophic bacterial and fungal counts: Ten - fold serial dilution of the cassava mill effluent sample was prepared. Aliquot 1ml of appropriate ten - fold serial dilution (10-3, 10-6 and 10-9) of the cassava mill effluent sample was inoculated into nutrient and potato dextrose agars plates containing fuscin and streptomycin in triplicate using pour plate method for bacterial and fungal enumeration respectively (Cheesbrough, 2006). Bacterial and fungal isolates were screened for their utilization of cassava mill effluent using a Mineral Salt Medium (MSM). MSM was used (for both cell suspensions and medium for the shake flask degradation test). Aliquot 0.2ml of the inoculum of bacteria and fungi (isolates and consortium) were dispensed into the flask containing sterilized cassava mill effluent and appropriate growth medium.
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