Isolation and screening of bioflocculant-producing bacteria from Richards Bay Harbour marine environment in South Africa

The search for biodegradable, economical and sustainable extracellular biopolymers from microorganism has been on the rise globally since chemical flocculants have been found to be hazardous to the environment. Marine sediments have been reported to contain a wide array of unique, diversified and novel organisms than those found in terrestrial and extreme environments that were once thought to be unfavourable to support their growth and the production of secondary metabolites as useful tools in biotechnology. Bacterial strains were isolated from soil, water and sediment samples collected from Richards Bay Harbour, Kwazulu Natal, South Africa. Their physiological and colonial characteristics were observed and recorded. Most of the isolates showed different range of white, yellow, pink, creamy, green and brown pigmented small to medium swarming colonies that were either raised or flat at the centre. Out of the initial mixed cultures, 22 pure isolates were screened for flocculating abilities using their crude extract. Among the screened isolates, three isolates showed significant flocculating activities greater than 70% in kaolin clay suspension (4.0 g/ L). The selected three isolates with their corresponding flocculating activities were preliminarily named as S1 (94%), S13 (97%) and S15 (74%), respectively. 16S rRNA identification revealed that S1, S13 and S15 were identified as Bacillus safensis, Bacillus pumilus and Bacillus atrophaeus, respectively. These three species of Bacillus have been observed to produce representative resistant endospore of the bacillus species and have been extensively studied in econiches of spacecraft and biodefence control interplanetary stations. The phylogenetic tree of the three organisms was constructed to show common ancestry as Bacillus species. However, based on the literature, unlike the Bacillus safensis and Bacillus pumilus; Bacillus atrophaeus was found for the first time to produce bioflocculants. The results showed that Richards Bay marine environment in South Africa as a reservoir for bioflocculants-producing bacteria with a potential to produce flocculants. The biotechnological importance of these isolated microorganism can be further achieved through optimisation of their culture conditions for bioflocculants production, extraction and characterisation of the produced bioflocculants.