Mass Transfer Performance of a String Film Reactor: A Bioreactor Design for Aerobic Methane Bioconversion

A shortcut to carbon-neutral bioplastic production: Recent advances in microbial production of polyhydroxyalkanoates from C1 resources

Since the 20th century, plastics that are widely being used in general life and industries are causing enormous plastic waste problems since improperly discarded plastics barely degrade and decompose. Thus, the demand for polyhydroxyalkanoates (PHAs), biodegradable polymers with material properties similar to conventional petroleum-based plastics, has been increased so far. The microbial production of PHAs is an environment-friendly solution for the current plastic crisis, however, the carbon sources for the microbial PHA production is a crucial factor to be considered in terms of carbon-neutrality. One‑carbon (C1) resources, such as methane, carbon monoxide, and carbon dioxide, are greenhouse gases and are abundantly found in nature and industry. C1 resources as the carbon sources for PHA production have a completely closed carbon loop with much advances; i) fast carbon circulation with direct bioconversion process and ii) simple fermentation procedure without sterilization as non-preferable nutrients. This review discusses the biosynthesis of PHAs based on C1 resource utilization by wild-type and metabolically engineered microbial host strains via biorefinery processes.

Chemoautotroph Cupriavidus necator as a potential game-changer for global warming and plastic waste problem: A review

Cupriavidus necator, a versatile microorganism found in both soil and water, can have both heterotrophic and lithoautotrophic metabolisms depending on environmental conditions. C. necator has been extensively examined for producing Polyhydroxyalkanoates (PHAs), the promising polyester alternatives to petroleum-based synthetic polymers because it has a superior ability for accumulating a considerable amount of PHAs from renewable resources. The development of metabolically engineered C. necator strains has led to their application for synthesizing biopolymers, biofuels and biochemicals such as ethanol, isobutanol and higher alcohols. Bio-based processes of recombinant C. necator have made much progress in production of these high-value products from biomass wastes, plastic wastes and even waste gases. In this review, we discuss the potential of C. necator as promising platform host strains that provide a great opportunity for developing a waste-based circular bioeconomy.

Cellulose nanocrystals coated with a tannic acid-Fe3+ complex as a significant medium for efficient CH4 microbial biotransformation

Microbial biotransformation of CH₄ gas has been attractive for the production of energy and high-value chemicals. However, insufficient supply of CH₄ in a culture medium needs to be overcome for the efficient utilization of CH₄. Here, we utilized cellulose nanocrystals coated with a tannic acid-Fe³⁺ complex (TA-Fe³⁺CNCs) as a medium component to enhance the gas-liquid mass-transfer performance. TA-Fe³⁺CNCs were well suspended in water without agglomeration, stabilized gas bubbles without coalescence, and increased the gas solubility by 20 % and the k_La value at a rapid inlet gas flow rate. Remarkably, the cell growth rate of Methylomonas sp. DH-1 as model CH₄-utilizing bacteria improved with TA-Fe³⁺CNC concentration without any cytotoxic or antibacterial properties, resulting in higher metabolite production ability such as methanol, pyruvate, formate, and succinate. These results showed that TA-Fe³⁺CNCs could be utilized as a significant component in the culture medium applicable as a promising nanofluid for efficient CH₄ microbial biotransformation.

Recent Advances on Biocatalysis and Metabolic Engineering for Biomanufacturing

The use of biocatalysts, including enzymes and metabolically engineered cells, has attracted a great deal of attention in chemical and bio-industry, because biocatalytic reactions can be conducted under environmentally-benign conditions and in more sustainable ways [...]