Modified biogenic nanocellulose and PHB from cacao fruit waste for enhanced mechanical and barrier performance of PHBV films

Abstract

Growing demand for sustainable packaging materials has intensified interest in polyhydroxyalkanoates (PHAs) as biodegradable alternatives to plastics. Among these, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV), a commercially available copolymer, shows promise for packaging but is hindered by limited mechanical strength and poor moisture resistance. We explore a biotechnological strategy to enhance PHBV film performance using two additives produced via microbial fermentation of effluents from cacao fruit processing: (i) TEMPO-oxidized bacterial cellulose (BC-TOCN) chemically modified by amidation with octadecyl amine (BC-TOCN-AMD C-18), and (ii) low-molecular-weight polyhydroxybutyrate (PHB). Hydrophobization of BC-TOCN-AMD C-18 was confirmed by a maximum water contact angle of 147°, higher than unmodified BC-TOCN, and decreased surface free energy (SFE) with minimal polar contribution.

Incorporating the two additives into PHBV films formed by melt extrusion increased the water contact angle from 89 to 112°, enhanced tensile strength from 0.50 to 5.5 MPa, and improved surface smoothness. Additionally, the films show 10.47 % reduction in water permeability and 9.54 % decrease in oxygen permeability compared to neat PHBV. These effects are attributed to synergistic interactions promoting improved dispersion and interfacial compatibility. The results highlight the potential of BC-based nanomaterials and homopolymeric PHB to modulate PHBV properties, supporting applications in sustainable packaging requiring moisture control and biodegradability.