Closing the Gap between Bio-Based and Petroleum-Based Plastic through Bioengineering

Bioplastics, which are plastic materials produced from renewable bio-based feedstocks, have been investigated for their potential as an attractive alternative to petroleum-based plastics. Despite the harmful effects of plastic accumulation in the environment, bioplastic production is still underdeveloped. Recent advances in strain development, genome sequencing, and editing technologies have accelerated research efforts toward bioplastic production and helped to advance its goal of replacing conventional plastics. In this review, we highlight bioengineering approaches, new advancements, and related challenges in the bioproduction and biodegradation of plastics. We cover different types of polymers, including polylactic acid (PLA) and polyhydroxyalkanoates (PHAs and PHBs) produced by bacterial, microalgal, and plant species naturally as well as through genetic engineering. Moreover, we provide detailed information on pathways that produce PHAs and PHBs in bacteria. Lastly, we present the prospect of using large-scale genome engineering to enhance strains and develop microalgae as a sustainable production platform.

Algal Cell Factories: Approaches, Applications, and Potentials

With the advent of modern biotechnology, microorganisms from diverse lineages have been used to produce bio-based feedstocks and bioactive compounds. Many of these compounds are currently commodities of interest, in a variety of markets and their utility warrants investigation into improving their production through strain development. In this review, we address the issue of strain improvement in a group of organisms with strong potential to be productive “cell factories”: the photosynthetic microalgae. Microalgae are a diverse group of phytoplankton, involving polyphyletic lineage such as green algae and diatoms that are commonly used in the industry. The photosynthetic microalgae have been under intense investigation recently for their ability to produce commercial compounds using only light, CO₂, and basic nutrients. However, their strain improvement is still a relatively recent area of work that is under development. Importantly, it is only through appropriate engineering methods that we may see the full biotechnological potential of microalgae come to fruition. Thus, in this review, we address past and present endeavors towards the aim of creating productive algal cell factories and describe possible advantageous future directions for the field.

Innate immunity at the mucosal surface: role of toll-like receptor 3 and toll-like receptor 9 in cervical epithelial cell responses to microbial pathogens

Toll-like receptors (TLRs) are a family of pattern recognition receptors that recognize distinct molecular patterns shared by a broad range of pathogens, including nucleic acids. TLR9, for example, recognizes unmethylated deoxycytidyl-phosphate-deoxyguanosine (CpG) dinucleotides that are common in bacterial and some viral nucleic acids, whereas TLR3 recognizes double-stranded RNA and TLR7/TLR8 recognize single-stranded RNA, which would be found during viral replication. We were interested in whether TLR3, TLR9, and the related TLR9 family members TLR7/TLR8 might play a role in antiviral immune defense at the mucosal epithelial surface of the lower female reproductive tract. We studied cervical epithelial cells and found that they expressed mRNA for TLR3, TLR9, and TLR7, but had only a weak signal for TLR8. For TLR3 and TLR9, protein expression was confirmed to be intracellular. When epithelial cells were incubated with polyinosine-polycytidylic acid and CpG oligodinucleotides, we observed dose-dependent upregulation of interleukin-8 secretion. However, cells failed to respond to a variety of TLR7/TLR8 ligands. Polyinosine-polycytidylic acid also induced production of interferon-beta and chemokine C-C motif ligand 5, whereas CpG DNA did not. Cell activation by synthetic oligodinucleotides occurred only in response to the B class sequences, and required the presence of human-specific CpG motifs. In addition, responses to CpG oligodinucleotides could be inhibited by chloroquine, demonstrating the requirement for endosomal maturation. These data demonstrate that mucosal epithelial cells express functional TLR3 and TLR9, and suggest that these receptors play a role in regulating the proinflammatory cytokine and antiviral environment of the lower female reproductive tract during infection with viral and bacterial pathogens.