Structure Assessment and Impacts of Lipids' Chemistry on the Structuration of Polyhydroxyalkanoate Biosynthesized by Bacillus licheniformis AZU-A5

Abstract

The current study exploited cheese whey supernatant (CWS) as a renewable resource for polyhydroxyalkanoates (PHAs) formation. Structure identification and investigating the influence of lipid membranes' chemistry on PHA structuration were detailed. Approximately 66 bacterial isolates from dairy products companies in Egypt were screened for PHA production, and the bacterial isolate AZU-A5, identified as Bacillus licheniformis strain AZU-A5, showed the highest production PHA 0.93 g L⁻¹) using whey lactose. The highest PHA rate in the individual design was 1.59 g L⁻¹ with a recovery yield of 33.08% (w w⁻¹), while the production rate in the statistical design reached 1.75 g L⁻¹ PHA and 51.60% PHA content. Structurally, the PHA was identified as polyhydroxy-3R-butyrate (R-PH3B). The fibrous texture by SEM highlighted the self-assembly of PHB. The CD analysis of the PHA films suggested favorable hydrophobic interactions between lipids and PHB. Higher lipid contents not only caused a decrement in the CD signal of PHB but also bathochromic effects occurred. The chain length of lipids exerted high impacts on interactions (CD) and structuration of PHB (Δλ). The unsaturation showed little influence on CD and negligible effect on Δλ, while the head group exerted no effect on CD with a considerable impact on Δλ.