EVALUATION OF STORAGE TEMPERATURES TO MEET SHELF LIFE REQUIREMENT FOR ACINETOBACTER BAUMANNII BIOFERTILIZER PRODUCT

Abstract

Acinetobacter baumannii (AP1) multifunctional biofertilizer bacterium has capabilities of atmospheric nitrogen (N₂) fixation, phosphate and potassium solubilisation and antagonism towards bacterial wilt disease of crops. AP1 is commercialised as GoGrow BioNPK. Shelf life study is essential for any commercial biofertilizer product. The minimum shelf life requirement for a biofertilizer product is six months. Optimum storage conditions, especially suitable storage temperatures are crucial, whereby the population of viable biofertilizer bacterial cells do not fall to below 10⁸ colony forming unit per ml (cfu ml^-1). The objective of this study was to determine the shelf life of AP1 at cool and room temperatures. Two categories of AP1 concentration were prepared, viz. mother culture concentration (10¹¹ cfu mL^-1) and commercial product concentration (10⁹ cfu mL^-1) . The samples were kept at cool temperature (6 + 2 ^oC) and room temperature (28 + 2^oC) for six months. The viable population of AP1 was determined monthly by the serial dilution method. Results showed survival of AP1 cells and viable population of AP1 remained at around 10⁸ cfu mL^-1 at six months storage, indicating that AP1 met the product specification either stored at cool temperature or at room temperature. Thus, AP1 is considered as a good biofertilizer product due to its long shelf life, beyond the minimum requirement of 10⁸cfu mL^-1 as set by Department of Agriculture Malaysia, at 6 months of storage.