The Catalytic Role of RuBisCO for in situ CO2 Recycling in Escherichia coli

Increase CO2 recycling of Escherichia coli containing CBB genes by enhancing solubility of multiple expressed proteins from an operon through temperature reduction

IMPORTANCE

In a previous study, we successfully engineered Escherichia coli capable of endogenous CO2 recycling through the heterologous expression of the Calvin-Benson Bassham genes. Establishing an efficient gene expression environment for recombinant strains is crucial, on par with the importance of metabolic engineering design. Therefore, the primary objective of this study was to further mitigate greenhouse gas emissions by investigating the effects of culture temperature on the formation of inclusion bodies (IB) and CO2 fixation activity in the engineered bacterial strain. The findings demonstrate that lowering the culture temperature effectively suppresses IB formation, enhances CO2 recycling, and concurrently increases the accumulation of organic acids. This temperature control approach, without adding or modifying compounds, is both convenient and efficient for enhancing CO2 recycling. As such, additional optimization of various environmental parameters holds promise for further enhancing the performance of recombinant strains efficiently.

Artificial Photosynthesis: Current Advancements and Future Prospects

Artificial photosynthesis is a technology with immense potential that aims to emulate the natural photosynthetic process. The process of natural photosynthesis involves the conversion of solar energy into chemical energy, which is stored in organic compounds. Catalysis is an essential aspect of artificial photosynthesis, as it facilitates the reactions that convert solar energy into chemical energy. In this review, we aim to provide an extensive overview of recent developments in the field of artificial photosynthesis by catalysis. We will discuss the various catalyst types used in artificial photosynthesis, including homogeneous catalysts, heterogeneous catalysts, and biocatalysts. Additionally, we will explore the different strategies employed to enhance the efficiency and selectivity of catalytic reactions, such as the utilization of nanomaterials, photoelectrochemical cells, and molecular engineering. Lastly, we will examine the challenges and opportunities of this technology as well as its potential applications in areas such as renewable energy, carbon capture and utilization, and sustainable agriculture. This review aims to provide a comprehensive and critical analysis of state-of-the-art methods in artificial photosynthesis by catalysis, as well as to identify key research directions for future advancements in this field.

The Transcription Activator AtxA from Bacillus Anthracis was Employed for Developing a Tight-Control, High-Level, Modulable, and Stationary-Phase Specific Transcription Activity in Escherichia Coli

The strong transcriptional activity of the virulent gene pagA in Bacillus anthracis has been proven to be anthrax toxin activator (AtxA)-regulated. However, the obscure pagA transcription mechanism hinders practical applications of this strong promoter. In this study, a 509-bp DNA fragment [termed 509sequence, (−508)-(+1) relative to the P2 transcription start site] was cloned upstream of rbs-GFPuv as pTOL02B to elucidate the AtxA-regulated transcription. The 509sequence was dissected into the −10 sequence, −35 sequence, AT_rich tract, SLI/SLII and upstream site. In conjunction with the heterologous co-expression of AtxA (under the control of the T7 promoter), the −10 sequence (TATACT) was sufficient for the AtxA-regulated transcription. Integration of pTOL02F + pTOLAtxA as pTOL03F showed that the AtxA-regulated transcription exhibited a strong specific fluorescence intensity/common analytical chemistry term (OD₆₀₀) of 40 597 ± 446 and an induction/repression ratio of 122. An improved induction/repression ratio of 276 was achieved by cultivating Escherichia coli/pTOL03F in M9 minimal medium. The newly developed promoter system termed P_AtxA consists of AtxA, the −10 sequence and Escherichia RNA polymerase. These three elements synergistically and cooperatively formed a previously undiscovered transcription system, which exhibited a tight-control, high-level, modulable and stationary-phase-specific transcription. The P_AtxA was used for phaCAB expression for the stationary-phase polyhydroxybutyrate production, and the results showed that a PHB yield, content and titer of 0.20 ± 0.27 g/g-glucose, 68 ± 11% and 1.5 ± 0.4 g/l can be obtained. The positive inducible P_AtxA, in contrast to negative inducible, should be a useful tool to diversify the gene information flow in synthetic biology.

Graphical Abstract

A Comparison of the Effects of Several Foliar Forms of Magnesium Fertilization on ‘Superior Seedless’ (Vitis vinifera L.) in Saline Soils

Magnesium (Mg) is the most essential element constituent in chlorophyll molecules that regulates photosynthesis processes. The physiological response of ‘Superior Seedless’ grapes was evaluated under different foliar magnesium fertilization such as sulfate magnesium (MgSO4·7 H2O), magnesium disodium EDTA (Mg-EDTA), and magnesium nanoparticles (Mg-NPs) during the berry development stages (flowering, fruit set, veraison, and harvest). In general, the ‘Superior Seedless’ vine had a higher performance in photosynthesis with Mg-NPs application than other forms. The Fy/Fm ratio declined rapidly after the fruit set stage; then, it decreased gradually up until the harvesting stage. However, both MgSO4 and Mg-EDTA forms showed slight differences in Fv/Fm ratio during the berry development stages. The outcomes of this research suggest that the Fv/Fm ratio during the growth season of the ‘Superior Seedless’ vine may be a good tool to assess magnesium fertilization effects before visible deficiency symptoms appear. Mg-NPs are more effective at improving ‘Superior Seedless’ berry development than the other magnesium forms. These findings suggest that applying foliar Mg-NPs to vines grown on salinity-sandy soil alleviates the potential Mg deficiency in ‘Superior Seedless’ vines and improves bunches quality.

Non-Photosynthetic CO2 Utilization to Increase Fatty Acid Production in Yarrowia lipolytica

Metabolic engineering of non-photosynthetic microorganisms to increase the utilization of CO₂ has been focused on as a green strategy to convert CO₂ into valuable products such as fatty acids. In this study, a CO₂ utilization pathway involving carbonic anhydrase and biotin carboxylase was formed to recycle CO₂ in the oleaginous yeast Yarrowia lipolytica, thereby increasing the production of fatty acids. In the recombinant strain in which the CO₂ utilization pathway was introduced, the production of fatty acids was 10.7 g/L, which was 1.5-fold higher than that of the wild-type strain. The resulting strain had a 1.4-fold increase in dry cell mass compared to the wild-type strain. In addition, linoleic acid was 47.7% in the fatty acid composition of the final strain, which was increased by 11.6% compared to the wild-type strain. These results can be applied as an essential technology for developing efficient and eco-friendly processes by directly utilizing CO₂.

Growth Enhancement Facilitated by Gaseous CO2 through Heterologous Expression of Reductive Tricarboxylic Acid Cycle Genes in Escherichia coli

The enzymatic mechanisms of carbon fixation by autotrophs, such as the reductive tricarboxylic acid cycle (rTCA), have inspired biotechnological approaches to producing bio-based chemicals directly through CO2. To explore the possibility of constructing an rTCA cycle in Escherichia coli and to investigate their potential for CO2 assimilation, a total of ten genes encoding the key rTCA cycle enzymes, including α-ketoglutarate:ferredoxin oxidoreductase, ATP-dependent citrate lyase, and fumarate reductase/succinate dehydrogenase, were cloned into E. coli. The transgenic E. coli strain exhibited enhanced growth and the ability to assimilate external inorganic carbon with a gaseous CO2 supply. Further experiments conducted in sugar-free medium containing hydrogen as the electron donor and dimethyl sulfoxide (DMSO) as the electron acceptor proved that the strain is able to undergo anaerobic respiration, using CO2 as the major carbon source. The transgenic stain demonstrated CO2-enhanced growth, whereas the genes involved in chemotaxis, flagellar assembly, and acid-resistance were upregulated under the anaerobic respiration. Furthermore, metabolomic analysis demonstrated that the total concentrations of ATP, ADP, and AMP in the transgenic strain were higher than those in the vector control strain and these results coincided with the enhanced growth. Our approach offers a novel strategy to engineer E. coli for assimilating external gaseous CO2.