A review on enzymes and pathways for manufacturing polyhydroxybutyrate from lignocellulosic materials

Production and functionalization strategies for superior polyhydroxybutyrate blend performance

This study investigates the effects of blending poly(3-hydroxybutyrate) (PHB) with microcrystalline cellulose (MCC), polylactic acid (PLA), lignin, and polyethylene glycol (PEG) on the properties of the resulting composite materials. Using a melt blending method, the composites were characterized by scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), and thermogravimetric analysis (TGA). The results reveal that blending PHB with MCC, PLA, lignin, and PEG significantly enhances the thermal stability, mechanical strength, and biodegradability of the composites compared to pure PHB. Specifically, the tensile strength of PHB-PLA blends increased by up to 47.77 MPa, compared to 27.16 MPa for pure PHB. The blend with 50 % cellulose content showed the highest tensile strength of 54.91 MPa. TGA results show that the PHB-MCC and PHB-lignin blends exhibit improved thermal stability, with onset degradation temperatures rising to 294.8 °C, compared to 275 °C for pure PHB. Moreover, the PHB-lignin blend demonstrated a gradual weight loss starting at 200 °C and continuing until about 350 °C. SEM images of the blends indicate a uniform microstructure, contributing to the improved mechanical properties. The PHB-PEG blend demonstrated an elongation at break of 4.34 %, significantly higher than the 2.15 % for pure PHB, highlighting its suitability for applications requiring pliable materials. The biodegradability tests showed that PHB-PLA blends maintained consistent degradation rates, making them advantageous for applications needing controlled biodegradability. These findings suggest that blending PHB with MCC, PLA, lignin, and PEG can produce materials with enhanced properties suitable for applications in packaging, biomedical devices, and other areas where both performance and sustainability are essential.

Current advances and emerging trends in sustainable polyhydroxyalkanoate modification from organic waste streams for material applications

The current processes for producing polyhydroxyalkanoates (PHAs) are costly, owing to the high cost of cultivation feedstocks, and the need to sterilise the growth medium, which is energy-intensive. PHA has been identified as a promising biomaterial with a wide range of potential applications and its functionalization from waste streams has made significant advances recently, which can help foster the growth of a circular economy and waste reduction. Recent developments and novel approaches in the functionalization of PHAs derived from various waste streams offer opportunities for addressing these issues. This study focuses on the development of sustainable, efficient, and cutting-edge methods, such as advanced bioprocess engineering, novel catalysts, and advances in materials science. Chemical techniques, such as epoxidation, oxidation, and esterification, have been employed for PHA functionalization, while enzymatic and microbial methods have indicated promise. PHB/polylactic acid blends with cellulose fibers showed improved tensile strength by 24.45-32.08 % and decreased water vapor and oxygen transmission rates while PHB/Polycaprolactone blends with a 1:1 ratio demonstrated an elongation at break four to six times higher than pure PHB, without altering tensile strength or elastic modulus. Moreover, PHB films blended with both polyethylene glycol and esterified sodium alginate showed improvements in crystallinity and decreased hydrophobicity.

Inhibitor formation and detoxification during lignocellulose biorefinery: A review

For lignocellulose biorefinery, pretreatment is needed to maximize the cellulose accessibility, frequently generating excess inhibitory substances to decline the efficiency of the subsequent fermentation processes. This mini-review updates the current research efforts to detoxify the adverse impacts of generated inhibitors on the performance of biomass biorefinery. The lignocellulose pretreatment processes are first reviewed. The generation of inhibitors, furans, furfural, phenols, formic acid, and acetic acid, from the lignocellulose, with their action mechanisms, are listed. Then the detoxification processes are reviewed, from which the biological detoxification processes are noted as promising and worth further study. The challenges and prospects for applying biological detoxification in lignocellulose biorefinery are outlined. Integrated studies considering the entire biorefinery should be performed on a case-by-case basis.