Multiple fluorescence labeling and two dimensional FTIR-13C NMR heterospectral correlation spectroscopy to characterize extracellular polymeric substances in biofilms produced during composting.

Knowledge on the structure and function of extracellular polymeric substances (EPS) in biofilms is essential for understanding biodegradation processes. Herein, a novel method based on multiple fluorescence labeling and two-dimensional (2D) FTIR-(13)C NMR heterospectral correlation spectroscopy was developed to gain insight on the composition, architecture, and function of EPS in biofilms during composting. Compared to other environmental biofilms, biofilms in the thermophilic (>55 °C) and cooling (mature) stage of composting have distinct characteristics. The results of multiple fluorescence labeling demonstrated that biofilms were distributed in clusters during the thermophilic stage (day 14), and dead cells were detected. In the mature stage (day 26), the biofilm formed a continuous layer with a thickness of approximately 20-100 µm around the compost, and recolonization of cells at the surface of the compost was easily observed. Through 2D FTIR-(13)C NMR correlation heterospectral spectroscopy, the following trend in the ease of the degradation of organic compounds was observed: heteropolysaccharides > cellulose > amide I in proteins. And proteins and cellulose showed significantly more degradation than heteropolysaccharides. In summary, the combination of multiple fluorescence labeling and 2D correlation spectroscopy is a promising approach for the characterization of EPS in biofilms.

Fate of biopolymers during rapeseed meal and wheat bran composting as studied by two-dimensional correlation spectroscopy in combination with multiple fluorescence labeling techniques.

Detailed knowledge of the molecular events during composting is important in improving the efficiency of this process. By combining two-dimensional Fourier transform infrared (FTIR) correlation spectroscopy and multiple fluorescent labeling, it was possible to study the degradation of biopolymers during rapeseed meal and wheat bran composting. Two-dimensional FTIR correlation spectroscopy provided structural information and was used to deconvolute overlapping bands found in the compost FTIR spectra. The degradation of biopolymers in rapeseed meal and wheat bran composts followed the sequence: cellulose, heteropolysaccharides, and proteins. Fluorescent labeling suggested that cellulose formed an intact network-like structure and the other biopolymers were embedded in the core of this structure. The sequence of degradation of biopolymers during composting was related to their distribution patterns.

Characteristics of extracellular polymeric substances (EPS) fractions from excess sludges and their effects on bioflocculability.

Extracellular polymeric substances (EPS) of biological origin are ubiquitous in excess sludges and can be applied as an underlying bioflocculant, owing to their high content of macromolecules and cations. However, low flocculating activity limits the feasibility of their practical applications. This study provides a novel EPS fractionation approach to improve their flocculability by extracting an active EPS fraction and removing the others with low flocculability. The results showed that for two excess sludges (called sludge A and sludge B), the tightly bound EPS (TB-EPS) fraction possessed a high flocculating rate to kaolin suspension compared with the other EPS fractions [i.e., supernatant, slime, and loosely bound EPS (LB-EPS) fraction] (>54.1+/-1.4% vs <7.8+/-1.6%). High bioflocculability of TB-EPS fraction could be attributable to high contents of macromolecules (330-1200 kDa) and trivalent cations (Fe(3+) and Al(3+)). Further investigation reveals that the TB-EPS fraction caused aggregation of particles by bridging and sweep flocculation.

Enhanced aerobic granulation with extracellular polymeric substances (EPS)-free pellets.

Extracellular polymeric substances (EPSs) were secreted by cells after they agglomerated into a compact aggregate. This study shows that the EPS initially embedded in seed sludge before granulation may sterically slow subsequent microbe-microbe contact, thereby delaying aerobic granulation. Three identical bioreactors were used in this study using glucose as the sole carbon and energy source. Reactor 1 (R1) was seeded with EPS-free pellets and operated in sequencing batch reactor (SBR) mode. Reactor 2 (R2) was seeded with the original sludge flocs and operated in SBR mode. Reactor 3 (R3) was seeded with EPS-free pellets and operated in continuously stirred tank reactor (CSTR) mode. Granulation occurred in R1 earlier than in R2; the granules that formed in R1 were larger and more compact than those in R2 at the same cultivation time. The few mature granules in R3 suggest that aerobic granulation can occur in a CSTR when a reactor is seeded with EPS-free pellets.