Mechanical, antibacterial and biodegradable properties of starch film containing bacteriocin immobilized crystalline nanocellulose.

We reported the preparation of antibacterial corn starch film (57% reduction in bacterial count) with enhanced tensile strength (69%) by incorporating immobilized bacteriocin. Whisker shaped crystalline nanocellulose (CNC, length 71.2 ± 20.7 nm and width 27.8 ± 11.2 nm) was prepared from cotton linters by bio-mechanical process, having the degree of polymerization 250. Bacteriocins extracted from broth cultures of P. acidilactici and E. faecium were immobilized on the surface of CNC and used to reinforce the starch film. The biodegradability of reinforced films was affected due to the use of bacteriocin in fillers. Surface morphology and roughness of reinforced films were studied by SEM and AFM. In an ambient environment, the films incorporated with bacteriocin immobilized CNC stayed fresh for 28 days while that of bacteriocin alone had fungal degradation in 14 days. This supports the requirement of CNC immobilization for better stability of bacteriocin on storage.

Improving the stability of bacteriocin extracted from Enterococcus faecium by immobilization onto cellulose nanocrystals.

Enterococcus faecium (E. faecium) isolated from Vigna mungo (Black gram) produced bacteriocin that inhibits both Gram positive and Gram negative bacteria and better heat stability (100 °C for 30 min). The bacteriocin was sensitive to protease treatment and most active in acidic pH. Bacteriocin produced by Pediococcus acidilactici was used for comparison. To enhance stability for diversified applications, the bacteriocin was immobilized by physical adsorption onto cellulose nanocrystals (CNC) extracted from cotton linters. The bacteriocin immobilization yield was 64.91% for P. acidilactici and 53.63% for E. faecium. The bacteriocin immobilized CNC was characterized by DLS particle sizing, FTIR and AFM to evaluate size distribution, chemical nature and surface morphology. The bacteriocins immobilized on CNC showed 50% increase in stability in terms of antibacterial activity. The enzymatic synthesis of CNC in combination with physical adsorption immobilization method for bacteriocin makes it an efficient system of producing antibacterial nanofillers for food packaging and bio-composites applications.