Optimized cell growth and poly(3-hydroxybutyrate) synthesis from saponified spent coffee grounds oil

Effect of emulsified lipid and saponified lipid on the enzyme desizing of starch and its mechanism

To enhance the flexibility of starch film adhesion on yarns, sizing lipids (saponified lipid or emulsified lipid) must be added during the sizing process. However, different types of sizing lipids may have diverse combinations with starch to impact enzyme desizing. Therefore, this study investigated the effects of saponified lipid and emulsified lipid commonly used in warp sizing on the hydrolysis of starch. Additionally, the desizing efficiency and chain structure of desizing residues were analyzed. Experimental results demonstrated that the existence of saponified lipid or emulsified lipid led to a reduction in the degree of hydrolysis (1.1 % and 2.6 %, respectively) compared to the original corn starch. Notably, saponified lipid exhibited a relatively strong negative impact. Furthermore, the desizing efficiency decreased after adding emulsified lipid (1.2 %) or saponified lipid (2.9 %). Starch-lipid V-type complexes and physical hindrance could inhibit the enzyme desizing, resulting in a larger wavelength of maximum absorbance for desizing residues, along with higher molecular weight, z-average radius of gyration, and an increased proportion of long chains. The presence of saponified lipid significantly negatively influenced desizing, possibly due to the smaller particle size and propensity for complex formation with starch.

Genetic and process engineering for polyhydroxyalkanoate production from pre- and post-consumer food waste

Biopolymers produced as microbial carbon storage systems, such as polyhydroxyalkanoates (PHAs), offer potential to be used in place of petrochemically derived plastics. Low-value organic feedstocks, such as food waste, have been explored as a potential substrate for the microbial production of PHAs. In this review, we discuss the biosynthesis, composition and producers of PHAs, with a particular focus on the genetic and process engineering efforts to utilise non-native substrates, derived from food waste from across the entire supply chain, for microbial growth and PHA production. We highlight a series of studies that have achieved impressive advances and discuss the challenges of producing PHAs with consistent composition and properties from mixed and variable food waste and by-products.

Perceiving biobased plastics as an alternative and innovative solution to combat plastic pollution for a circular economy

Plastic waste from fossil-based sources, including single-use packaging materials, is continuously accumulating in landfills, and leaching into the environment. A 2021 UN Environment Programme (UNEP) report suggests that the plastic pollution is likely to be doubled by 2030, posing a major challenge to the environment and the overall global plastic waste management efforts. The use of biobased plastics such as polyhydroxyalkanoates (PHAs) as a biodegradable substitute for petroleum-based plastics could be a feasible option to combat this issue which may further result in much lower carbon emissions and energy usage in comparison to conventional plastics as additional advantages. Though recent years have seen the use of microbes as biosynthetic machinery for biobased plastics, using various renewable feedstocks, the scaled-up production of such materials is still challenging. The current study outlays applications of biobased plastics, potential microorganisms producing biobased plastics such as Cupriavidus necator, Bacillus sp., Rhodopseudomonas palustris, microalgae, and mixed microbial cultures, and inexpensive and renewable resources as carbon substrates including industrial wastes. This review also provides deep insights into the operational parameters, challenges and mitigation, and future opportunities for maximizing the production of biobased plastic products. Finally, this review emphasizes the concept of biorefinery as a sustainable and innovative solution for biobased plastic production for achieving a circular bioeconomy.

De Novo Synthesis of Poly(3-hydroxybutyrate-co-3-hydroxypropionate) from Oil by Engineered Cupriavidus necator

Poly(3-hydroxybutyrate-co-3-hydroxypropionate) [P(3HB-co-3HP)] is a biodegradable and biocompatible polyester with improved and expanded material properties compared with poly(3-hydroxybutyrate) (PHB). This study engineered a robust malonyl-CoA pathway in Cupriavidus necator for the efficient supply of a 3HP monomer, and could achieve the production of [P(3HB-co-3HP)] from variable oil substrates. Flask level experiments followed by product purification and characterization found the optimal fermentation condition (soybean oil as carbon source, 0.5 g/L arabinose as induction level) in general consideration of the PHA content, PHA titer and 3HP molar fraction. A 5 L fed-batch fermentation (72 h) further increased the dry cell weight (DCW) to 6.08 g/L, the titer of [P(3HB-co-3HP)] to 3.11 g/L and the 3HP molar fraction to 32.25%. Further improving the 3HP molar fraction by increasing arabinose induction failed as the engineered malonyl-CoA pathway was not properly expressed under the high-level induction condition. With several promising advantages (broader range of economic oil substrates, no need for expensive supplementations such as alanine and VB12), this study indicated a candidate route for the industrial level production of [P(3HB-co-3HP)]. For future prospects, further studies are needed to further improve the strain and the fermentation process and expand the range of relative products.