The aim of this study was to investigate the impact of polyhexamethylene guanidine hydrochloride
(PHMG) derivatives introduced into polyhydroxybutyrate (PHB) and polylactide (PLA) on biofilm formation
by Escherichia coli and Staphylococcus aureus on the surface of these composites. We also
determined bactericidal activity of the applied PHMG derivatives according to standard ISO 22196. The
composites were made of PLA and PHB containing PHMG stearate, PHMG granular polyethylene wax, and
PHMG salt of sulfanilic acid at concentrations ranging from 0.2 to 1.0 % (w:w). The results indicate that
PLA and PHB enriched with PHMG stearate and salt of sulfanic acid do not have bactericidal properties
(R < 2) while PLA and PHB enriched with PHMG granular polyethylene wax have bactericidal properties
(R > 2). Increased concentration of PHMG derivatives improved bactericidal activity of the investigated
composites thus inhibiting biofilm formation on their surface. The composite containing PHMG granular
polyethylene wax was the strongest inhibitor of biofilm formation by S. aureus.