Bioprospection of Commercially Important Alkaliphilic Bacteria From Soda Ash Industrial Effluent and Sludge Samples Near the Gulf of Khambhat, Gujarat, India

This study reports 110 different alkaliphilic bacteria isolated from soda ash industrial effluents and sludge samples, employing an innovative κ-carrageenan-KCl-based solid medium (pH 13.0 ± 0.2). Primarily, they were subjected to morphological, physiological, and biochemical tests. Molecular characterization was carried out using 16S rRNA sequence homology analysis. They were also screened for halo-alkaline extracellular enzyme production like amylase, pectinase, caseinase, gelatinase, lipase, and xylanase and antibiotic sensitivity. Their phylogenetic analysis revealed that these extreme alkaliphiles belonged to 26 diverse genera: (Firmicutes, 61%) Paenibacillus, Bacillus, Exiguobacterium, Lysinibacillus, Planomicrobium, Aneurinibacillus, Staphylococcus; (Proteobacteria, 21%) Pseudomonas, Stenotrophomonas, Enterobacter, Alishewanella, Rheinheimera, Brevundimonas, Ochrobactrum, Alcaligenes; (Actinobacteria, 18%) Cellulosimicrobium, Nesterenkonia, Arthrobacter, Rhodococcus, Microbacterium, Brevibacterium, Janibacter, Dietzia, Micrococcus, Kocuria, Streptomyces. Majority of them produced were lipase (73%), pectinase (72%), and caseinase (71%). Fifteen percent of them produced all six alkaline enzymes. A large amount of extracellular polysaccharide (EPS) was produced by 19% of isolates, which might be useful for petroleum hydrocarbon or heavy metal bioremediation. Sixteen percent of the isolates were resistant to ≥ 5 antibiotics. Highest antibiotic resistance was observed against ceftazidime (39.09%) and penicillin (26.36%), while netlimycin, amikacin, ciprofloxacin, and gentamicin proved most effective against 99%-98% of isolates. There were 27 isolates whose 16S rRNA sequences showed ≤ 97% homology with ones in NCBI, suggesting the possibility of novel lineages in phylogeny. This is the first attempt where a diverse population of commercially important alkaliphilic bacteria has been isolated and characterized from soda ash industry, effluent, and sludge samples by using a specially devised culture media.