The impact of cellulose nanocrystals on the aggregation and initial adhesion to a solid surface of Escherichia coli K12: Role of solution chemistry

Abstract

Aggregation of bacteria and their initial adhesion to silica surfaces are affected greatly by solution chemistry, particularly pH and ionic strength (IS). The effects of pH and IS on the aggregation and deposition of Escherichia coli K12 on silica surfaces were investigated in NaCl solutions at variable pH and IS, and in the absence and presence of cellulose nanocrystals (CNC). In the presence of CNC, bacterial aggregation was generally enhanced as the pH was increased from 3.5 to neutral at a given IS (10mM). At a given pH (7.2), bacterial aggregation was highest at 10mM as the IS was increased from 1mM to 50mM. The contribution of DLVO interaction and depletion interaction to bacterial aggregation in the bacteria and CNC system was compared. The results indicate that at pH ranging from 5.2 to 7.2 and IS ranging from 10mM to 50mM conditions, depletion attraction is the dominant mechanism for CNC induced bacterial aggregation. The lower bacterial deposition rates observed at 10mM IS and pH 7.2 compared with other conditions were mainly attributed to the aggregation of bacteria which could result in decreased convective-diffusive transport to the silica surface.