A novel thermally stable heteropolysaccharide-based bioflocculant from hydrocarbonoclastic strain Kocuria rosea BU22S and its application in dye removal

A new bioflocculant named pKr produced by hydrocarbonoclastic strain Kocuria rosea BU22S
(KC152976) was investigated. Gas chromatography–flame ionization detector (GC-FID) analysis
confirmed the high potential of the strain BU22S in the degradation of n-alkanes. Plackett–
Burman experimental design and response surface methodology were carried out to optimize
pKr production. Glucose, peptone and incubation time were found to be the most significant
factors affecting bioflocculant production. Maximum pKr production was about 4.72 ± 0.02 g/L
achieved with 15.61 g/L glucose, 6.45 g/L peptone and 3 days incubation time. Chemical analysis
of pKr indicated that it contained 71.62% polysaccharides, 16.36% uronic acid and 2.83%
proteins. Thin layer chromatography analysis showed that polysaccharides fraction consisted of
galactose and xylose. Fourier transform infrared analysis revealed the presence of many
functional groups, hydroxyl, carboxyl, methoxyl, acetyl and amide that likely contribute to
flocculation. K. rosea pKr showed high flocculant potential using kaolin clay at different pH (2–
11), temperature (0–100°C) and cation concentrations. The bioflocculant was particularly effective
in flocculating soluble anionic dyes, Reactive Blue 4 and Acid Yellow, with a decolorization
efficiency of 76.4% and 72.6%, respectively. The outstanding flocculating performances suggest
that pKr could be useful for bioremediation applications.