Optimization of α-Amylase Production by Enterobacter cloacae Strain D1 Isolated from Cassava Effluent-impacted Soil Using Response Surface Methodology

Background: Production of amylase by Enterobacter cloacae D1 was optimized in this study using central composite design (CCD) of response surface methodology (RSM). 
Methodology: Effects of five numeric factors (pH, temperature, inoculum concentration, peptone and yeast extract) on the production of amylase were examined. Amylase production was first screened using plate technique and amylase assay thereafter carried out using the dinitrosalicylic acid (DNSA) method. The CCD-RSM experimental set-up involved 30 runs with 5 levels of independent variables. 
Results: The amylase-producing bacterium Enterobacter cloacae strain D1 was identified based on the phylogenetic tree analysis of its sequence. The sequence has been submitted to GenBank under the accession number: MZ477010. The isolate had 98% similarity to the GenBank match Enterobacter cloacae strain ATCC 13182. Optimum conditions that yielded maximum amylase (34.43 U/mL) were pH 5; temperature 40 ℃; inoculum concentration 3%; peptone 1.2% and yeast extract 0.5%. 
Conclusion: This study has demonstrated efficient amylase production from Enterobacter cloacae strain D1 isolated from cassava effluent-impacted soil from Rumuosi, Port Harcourt, Rivers State. In addition, optimization of the critical factors of amylase production resulted in 3.4 fold increase in amylase activity. The enhancement of amylase production by the RSM techniques shows that amylase from this strain can be scaled-up for industrial application.