Efficient production of chemicals from microorganism by metabolic engineering and synthetic biology

The use of traditional chemical catalysis to produce chemicals has a series of drawbacks,such as high dependence on fossil resources,high energy consumption,and environmental pollution.With the development of synthetic biology and metabolic engineering,the use of renewable biomass raw materials for chemicals synthesis by constructing efficient microbial cell factories is a green way to replace traditional chemical catalysis and traditional microbial fermentation.This review mainly summarizes several types of bulk chemicals and high value-added chemicals using metabolic engineering and synthetic biology strategies to achieve efficient microbial production.In addition,this review also summarizes several strategies for effectively regulating microbial cell metabolism.These strategies can achieve the coupling balance of material and energy by regulating intracellular material metabolism or energy metabolism,and promote the efficient production of target chemicals by microorganisms.

Pilot-scale acetone-butanol-ethanol fermentation from corn stover

Biobutanol is an advanced biofuel that can be produced from excess lignocellulose via acetone-butanol-ethanol(ABE)fermentation.Although significant technological progress has been made in this field,attempts at largescale lignocellulosic ABE production remain scarce.In this study,1m^(3)scale ABE fermentation was investigated using high inhibitor tolerance Clostridium acetobutylicum ABE-P1201 and steam-exploded corn stover hydrolysate(SECSH).Before expanding the fermentation scale,the detoxification process for SECSH was simplified by process engineering.Results revealed that appropriate pH management during the fed-batch cultivation could largely decrease the inhibition of the toxic components in undetoxified SECSH to the solventogenesis phase of the ABE-P1201 strains,avoiding“acid crash”.Therefore,after naturalizing the pH by Ca(OH)_(2),the undetoxified SECSH,without removal of the solid components,reached 17.68±1.30 g/L of ABE production with 0.34±0.01 g/g of yield in 1 L scale bioreactor.Based on this strategy,the fermentation scale gradually expanded from laboratory-scale apparatus to pilot-scale bioreactors.Finally,17.05±1.20 g/L of ABE titer and 0.32±0.01 g/g of ABE yield were realized in 1m3 bioreactor,corresponding to approximately 145 kg of ABE production from 1 t of dry corn stover.The pilot-scale ABE fermentation demonstrated excellent stability during repeated operations.This study provided a simplified ABE fermentation strategy and verified the feasibility of the pilot process,providing tremendous significance and a solid foundation for the future industrialization of second-generation ABE plants.

Investigating formate tolerance mechanisms in Saccharomyces cerevisiae and its application

Current global energy and environmental crisis have spurred efforts towards developing sustainable biotechnological solutions,such as utilizing CO_(2) and its derivatives as raw materials.Formate is an attractive onecarbon source due to its high solubility and low reduction potential.However,the regulatory mechanism of formate metabolism in yeast remains largely unexplored.This study employed adaptive laboratory evolution(ALE)to improve formate tolerance in Saccharomyces cerevisiae and characterized the underlying molecular mechanisms.The evolved strain was applied to produce free fatty acids(FFAs)under high concentration of formate with glucose addition.The results showed that the evolved strain achieved a FFAs titer of 250 mg/L.Overall,this study sheds light on the regulatory mechanism of formate tolerance and provides a platform for future studies under high concentrations of formate.

Massive and parallel 10 Tbit/s physical random bit generation with chaotic microcomb

Ultrafast physical random bit(PRB)generators and integrated schemes have proven to be valuable in a broad range of scientifc and technological applications.In this study,we experimentally demonstrated a PRB scheme with a chaotic microcomb using a chip-scale integrated resonator.A microcomb contained hundreds of chaotic channels,and each comb tooth functioned as an entropy source for the PRB.First,a 12 Gbits/s PRB signal was obtained for each tooth channel with proper post-processing and passed the NIST Special Publication 800-22 statistical tests.The chaotic microcomb covered a wavelength range from 1430 to 1675 nm with a free spectral range(FSR)of 100 GHz.Consequently,the combined random bit sequence could achieve an ultra-high rate of about 4 Tbits/s(12 Gbits/s×294=3.528 Tbits/s),with 294 teeth in the experimental microcomb.Additionally,denser microcombs were experimentally realized using an integrated resonator with 33.6 GHz FSR.A total of 805 chaotic comb teeth were observed and covered the wavelength range from 1430 to 1670 nm.In each tooth channel,12 Gbits/s random sequences was generated,which passed the NIST test.Consequently,the total rate of the PRB was approximately 10 Tbits/s(12 Gbits/s×805=9.66 Tbits/s).These results could ofer potential chip solutions of Pbits/s PRB with the features of low cost and a high degree of parallelism.