Phenotypic Characterization of Pectinase-Producing Alkaliphilic Microbial Isolates From Lake Bogoria, Baringo County, Kenya

Alkaline pectinases are in demand in industrial processes that require the degradation of plant pectins at high pH, for example, removal of pectin stains from fabrics, cutlery, and porcelain; treatment of pectic wastewater; fermentation of coffee, tea, and cocoa; manufacture of poultry and animal feeds, and processing of textiles, and so forth. The present study aimed to (a) screen four alkaliphilic microbial isolates, previously obtained from samples collected around Lake Bogoria (soda lake), Baringo County, Kenya, for alkaline pectinases, and (b) characterize the pectinase-producers. The screening data revealed that all the isolates were pectinase producers, exhibiting catalytic activities that ranged from 1.4 to 1.6 pectinolytic indices (PI) (primary screening) and 0.04–0.15 U/mL (secondary screening). These isolates' colonies, which featured smooth textures and umbonate elevations, were moist, white, or cream. Their cells were motile, aerobic rods that were Gram-, catalase-, and oxidase-positive. In addition, they a) utilized inositol, sucrose, lactose, and glucose, and b) hydrolyzed starch, pullulan, casein, and gelatin. Furthermore, they grew optimally at pH 10.5, 45°C, and in the absence of NaCl but tolerated growth at higher temperatures (up to 55°C) and saline conditions [up to 12.5% (w/v) NaCl]. No growth was detected at neutral pH. Based on these phenotypic characteristics, the indigenous pectinase-producing microbial isolates from Lake Bogoria were identified as thermo-halo-tolerant obligate alkaliphiles that belonged to the species Bacillus halodurans. The alkaline pectinases that they produced can potentially find applications in the fore-mentioned local industrial processes, if harnessed.