Isolation and identification of thermostable amylase enzyme producing bacteria from compost production plant in Kurunegala

Abstract

Thermostable enzymes play a vital role in various industrial sectors due to their ability to function efficiently at elevated temperatures. Thermostable amylase is one such enzyme widely utilized in numerous industrial applications. Therefore, isolating locally available thermostable amylase-producing bacteria is essential to meet the increasing demand for these enzymes. This study aimed to isolate and identify thermostable amylase-producing bacteria from hot soil. Soil samples were collected from the municipal solid waste compost production plant in Sundarapola, Kurunegala (7° 30' 31.50" N, 80° 21' 9.84" E). Bacterial colonies were isolated using the standard pour plate method on Nutrient Agar (NA) at room temperature. Amylase-producing bacteria were identified through the starch hydrolysis test. The amylase activity of crude enzyme extracts was determined using the Di-nitrosalicylic acid (DNS) method. Optimum temperature and pH for enzyme activity were evaluated, and the most promising isolate was identified using 16S rRNA gene sequencing. The soil samples were collected from a location with a temperature of approximately 60 °C. Out of ten morphologically distinct bacterial isolates obtained, three (SP1, SP5, SP7) tested positive for amylase production. The isolate SP5 exhibited the highest amylase activity (1.434 U mL⁻¹) at room temperature (29 °C), whereas SP1, identified as Bacillus pumilus, demonstrated the highest amylase activity (2.282 U mL⁻¹) at its optimum temperature of 60 °C. The optimum pH for enzyme activity was recorded as pH 7. Based on these findings, the B. pumilus isolate from the Sundarapola compost production plant shows strong potential for use in industrial processes that operate at high temperatures. Further studies are recommended to optimize culture conditions and additional factors influencing enzyme activity to facilitate successful industrial application of these thermostable enzymes.