Microalgal Biomass as Feedstock for Bacterial Production of PHA: Advances and Future Prospects

Abstract

The search for biodegradable plastics has become the focus in combating the global plastic pollution crisis. Polyhydroxyalkanoates (PHAs) are renewable substitutes to petroleum-based plastics with the ability to completely mineralize in soil, compost, and marine environments. The preferred choice of PHA synthesis is from bacteria or archaea. However, microbial production of PHAs faces a major drawback due to high production costs attributed to the high price of organic substrates as compared to synthetic plastics. As such, microalgal biomass presents a low-cost solution as feedstock for PHA synthesis. Photoautotrophic microalgae are ubiquitous in our ecosystem and thrive from utilizing easily accessible light, carbon dioxide and inorganic nutrients. Biomass production from microalgae offers advantages that include high yields, effective carbon dioxide capture, efficient treatment of effluents and the usage of infertile land. Nevertheless, the success of large-scale PHA synthesis using microalgal biomass faces constraints that encompass the entire flow of the microalgal biomass production, i.e., from molecular aspects of the microalgae to cultivation conditions to harvesting and drying microalgal biomass along with the conversion of the biomass into PHA. This review discusses approaches such as optimization of growth conditions, improvement of the microalgal biomass manufacturing technologies as well as the genetic engineering of both microalgae and PHA-producing bacteria with the purpose of refining PHA production from microalgal biomass.

An Alternative Exploitation of Synechocystis sp. PCC6803: A Cascade Approach for the Recovery of High Added-Value Products

“…To the best of our knowledge, this is the first evidence of PHA production starting from lipids obtained by microalgae in a cascade approach. Indeed, only carbohydrates from microalgal hydrolysate have been used as carbon source for the production of PHA through bacterial fermentation [ 33 ], or, as an alternative, genetically modified Synechocystis has been used as an eco-friendly alternative in the bioplastic production [ 34 ]. PHAs represent a high added-value product, with their market expected to reach USD 167 million by 2027, at a CAGR of 15.3% from USD 81 million in 2022 ( , accessed on 14 February 2023).…”

A potential paradigm in CRISPR/Cas systems delivery: at the crossroad of microalgal gene editing and algal-mediated nanoparticles

“…Although CRISPR/Cas systems have demonstrated great promise in the field of microalgae, their application may be hampered by a lack of understanding of microalgal biology, inefficient delivery of genetic materials, decreased expression of Cas9 due to unknown factors, low repair efficiency of the homology-directed repair (HDR) pathway, and other factors [ 250 ]. (1) Microalgae bioengineering is still in its infancy, with only a few fully sequenced genome species [ 251 ]. In the field of microalgal research, artificial intelligence (AI) has gained popularity and can be used to predict gene sequencing and editing.…”