Extracellular polymeric substances production kinetics of 13 sludge isolates using wastewater sludge as raw material and its flocculation potential

Abstract

The kinetics of batch fermentation of 13 extracellular polymeric substances (EPS) producing bacterial strains (9 Bacillus, 2 Serratia and 2 Yersinia) were carried out using sterilized sludge as a raw material. The most of Bacillus (µ(max): 0.11-0.27 h⁻¹), Serratia (µ(max): 0.23-0.27 h⁻¹) and Yersinia (µ(max): 0.18-0.19 h⁻¹) strains had capability to grow and produce EPS (1.36-2.12 g/L) in the sterilized sludge. In general, EPS production was mixed growth associated for all the bacterial strains cultivated independently. Bacillus sp. 7, Serratia sp. 2 and Yersinia sp. 2 produced higher concentration (1.95-2.12 g/L) of EPS than the other remaining bacterial strains. Protein and carbohydrate contents of EPS remained constant during fermentation. Broth EPS (B-EPS) exhibited high kaolin flocculation activity (≥ 75%) in most of the cases except Bacillus sp. 1, Bacillus sp. 5 and Bacillus sp. 9, respectively. In general, high flocculation activities (FAs) (≥ 75%), were attained using 1.31-1.70 mg B-EPS/g kaolin, 0.45-0.97 mg protein/g kaolin and 0.11-0.21 mg carbohydrates/g kaolin. The study suggests that further systematic exploration is required for optimizing the process of EPS production. EPS produced in the sludge can potentially be used for different water and wastewater treatments.

Characterization of Extracellular Polymeric Substances (Eps) Produced by Cloacibacterium normanense Isolated from Wastewater Sludge for Sludge Settling and Dewatering

“…A decrease in B-EPS concentration (from 13.3 to 11.4 g/L) was observed between 48 and 96 h. This decrease could be due to the fact that the bacteria may have consumed EPS when carbon limitation occurred in the medium. This phenomenon was also observed by other researchers using pure or mixed culture in sludge or synthetic medium [2,16]. According to More et.…”

“…al. [2] investigated the effect of fermentation time on EPS production in activated sludge and found that the EPS content was proportional to the bacterial growth. A decrease in B-EPS concentration (from 13.3 to 11.4 g/L) was observed between 48 and 96 h. This decrease could be due to the fact that the bacteria may have consumed EPS when carbon limitation occurred in the medium.…”

“…Better dewaterability leads to a sludge economical disposal, reuse as a soil conditioner in agriculture, bricks for construction, and raw material for growing industrial microorganisms [1]. In recent years, researchers have been venturing into bioflocculation of sludge using microorganisms [2]. Bioflocculation is defined as an aggregation of bacterial flocs and it is utmost important for efficient separation of microorganisms from the treated effluent.…”

“…The bacterial EPSs are usually acidic heteropolysaccharides possessing different functional groups (e.g., hydroxyl, carboxyl and phosphoric acid), which exhibit high affinity towards certain metal ions. Many physical and chemical properties of microbial EPSs have led to a wide range of field applications, e.g., adhesion, chelation of heavy metals, coagulation and flocculation, detoxification of toxic compounds, nutrient sequestration, protection against osmotic shock, stabilizers, thickeners, gelling, film-forming and water-retention capability (in detergents, textiles, adhesives, paper, paint, food and beverage industries), oil recovery, mining industry and petroleum industries [2]. A wide range of bacteria from various environmental habitats are known to produce complex and diverse EPS occurring as capsular polysaccharides (C-EPS, strongly associated with the cell surface) or as slime polysaccharides (S-EPS, loosely associated with the cell).…”

Effect of Sludge Concentration and Crude Glycerol Matrix as a Substrate on the Production of Single-Cell Oil by Oleaginous Yeast Yarrowia lipolytica SKY7

“…The sludge media was prepared using different sludge solid concentrations (5,10,20,30 The crude glycerol used in this experiment was obtained from Bio-Liq, Quebec, Canada. The crude glycerol contained 675 g/L of glycerol.…”