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1. Electrosynthesis of amino acids from biomass-derived α-hydroxyl acids

   https://doi.org/10.1039/d2gc01779b  

   Yan, Kaili; Huddleston, Morgan L.; Gerdes, Brett A.; Sun, Yujie (July 2022, Green Chemistry)

   Electrochemical conversion of biomass-derived intermediate compounds to high-value products has emerged as a promising approach in the field of biorefinery. Biomass upgrading allows for the production of chemicals from non-fossil-based carbon sources and capitalization on electricity as a green energy input. Amino acids, as products of biomass upgrading, have received relatively little attention. Pharmaceutical and food industries will benefit from an alternative strategy for the production of amino acids that does not rely on inefficient fermentation processes. The use of renewable biomass resources as starting materials makes this proposed strategy more desirable. Herein, we report an electrochemical approach for the selective oxidation of biomass-derived α-hydroxyl acids to α-keto acids, followed by electrochemical reductive amination to yield amino acids as the final products. Such a strategy takes advantage of both reactions at the anode and cathode and produces amino acids under ambient conditions with high energy efficiency. A flow electrolyzer was also successfully employed for the conversion of α-hydroxyl acids to amino acids, highlighting its great potential for large-scale application. 

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2. Discovery of l-threonine transaldolases for enhanced biosynthesis of beta-hydroxylated amino acids

   https://doi.org/10.1038/s42003-023-05293-0  

   Jones, Michaela A; Butler, Neil D; Anderson, Shelby R; Wirt, Sean A; Govil, Ishika; Lyu, Xinyi; Fang, Yinzhi; Kunjapur, Aditya M (September 2023, Communications Biology)

   Abstract Beta-hydroxy non-standard amino acids (β-OH-nsAAs) have utility as small molecule drugs, precursors for beta-lactone antibiotics, and building blocks for polypeptides. While the L-threonine transaldolase (TTA), ObiH, is a promising enzyme for β-OH-nsAA biosynthesis, little is known about other natural TTA sequences. We ascertained the specificity of the TTA enzyme class more comprehensively by characterizing 12 candidate TTA gene products across a wide range (20-80%) of sequence identities. We found that addition of a solubility tag substantially enhanced the soluble protein expression level within this difficult-to-express enzyme family. Using an optimized coupled enzyme assay, we identified six TTAs, including one with less than 30% sequence identity to ObiH that exhibits broader substrate scope, two-fold higher L-Threonine (L-Thr) affinity, and five-fold faster initial reaction rates under conditions tested. We harnessed these TTAs for first-time bioproduction of β-OH-nsAAs with handles for bio-orthogonal conjugation from supplemented precursors during aerobic fermentation of engineeredEscherichia coli, where we observed that higher affinity of the TTA for L-Thr increased titer. Overall, our work reveals an unexpectedly high level of sequence diversity and broad substrate specificity in an enzyme family whose members play key roles in the biosynthesis of therapeutic natural products that could benefit from chemical diversification. 

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3. Photodynamics of amino acids under UV excitation: Extraterrestrial amino acids

   https://doi.org/10.1063/5.0332342  

   Zeng, Jia; Sasselov, Dimitar D; Crespo-Hernández, Carlos E; Kufner, Corinna L (July 2026, The Journal of Chemical Physics)

   The detection of amino acids in extraterrestrial environments has important implications for astrobiology and prebiotic chemistry, yet the pathways to their syntheses and their photostability under such conditions remain unclear. In this study, we employ femtosecond UV-pump visible-probe spectroscopy to investigate the ultrafast relaxation dynamics of non-aromatic amino acids in aqueous environments, representative of those found in Murchison-type meteorites and pristine Bennu samples. Using excitation wavelengths around 210 nm and probing in the visible range, two distinct decay lifetimes are identified, revealing the coexistence of internal conversion and fluorescence decay mechanisms. Internal conversion lifetimes range from 25 to 32 ps, showing efficient non-radiative relaxation processes, while fluorescence decays have a slower timescale of about 1 ns. These findings can help clarify the excited-state relaxation pathways that influence the photostability and survival of these amino acids. 

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4. Protein storage and reproduction increase in grasshoppers on a diet matched to the amino acids of egg yolk protein

   https://doi.org/10.1242/jeb.244450  

   Hatle, John D.; Maslikova, Victoriya; Short, Clancy A.; Bracey, Donald; Darmanjian, Margaret; Morningstar, Sarah; Reams, Brooke; Mashanov, Vladimir S.; Jahan-Mihan, Alireza; Hahn, Daniel A. (September 2022, Journal of Experimental Biology)

   ABSTRACT The diets of animals are essential to support development, and protein is key. Accumulation of stored nutrients can support developmental events such as molting and initiation of reproduction. Agricultural studies have addressed how dietary protein quality affects growth, but few studies have addressed the effects of dietary protein quality on developmental transitions. Studies on how dietary quality may affect protein storage and development are possible in arthropods, which store proteins in the hemolymph. We hypothesized that diets with a composition of amino acids that matches the precursor of egg yolk protein (vitellogenin, Vg) will be high quality and support both egg production and accumulation of storage proteins. Grasshoppers were fed one of two isonitrogenous solutions of amino acids daily: Vg-balanced (matched to Vg) or Unbalanced (same total moles of amino acids, but not matched to egg yolk). We measured reproduction and storage protein levels in serial hemolymph samples from individuals. The Vg-balanced group had greater reproduction and greater cumulative levels of storage proteins than did the Unbalanced group. This occurred even though amino acids fed to the Vg-balanced group were not a better match to storage protein than were the amino acids fed to the Unbalanced group. Further, oviposition timing was best explained by a combination of diet, age at the maximum level of storage protein hexamerin-270 and accumulation of hexamerin-90. Our study tightens the link between storage proteins and commitment to reproduction, and shows that dietary protein quality is vital for protein storage and reproduction. 

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5. Hydrolysis of lignocellulose by anaerobic fungi produces free sugars and organic acids for two‐stage fine chemical production with Kluyveromyces marxianus

   https://doi.org/10.1002/btpr.3172  

   Hillman, Ethan T.; Li, Mengwan; Hooker, Casey A.; Englaender, Jacob A.; Wheeldon, Ian; Solomon, Kevin V. (April 2021, Biotechnology Progress)

   null (Ed.)

   Development of the bioeconomy is driven by our ability to access the energy-rich carbon trapped in recalcitrant plant materials. Current strategies to release this carbon rely on expensive enzyme cocktails and physicochemical pretreatment, producing inhibitory compounds that hinder subsequent microbial bioproduction. Anaerobic fungi are an appealing solution as they hydrolyze crude, untreated biomass at ambient conditions into sugars that can be converted into value-added products by partner organisms. However, some carbon is lost to anaerobic fungal fermentation products. To improve efficiency and recapture this lost carbon, we built a two-stage bioprocessing system pairing the anaerobic fungus Piromyces indianae with the yeast Kluyveromyces marxianus, which grows on a wide range of sugars and fermentation products. In doing so we produce fine and commodity chemicals directly from untreated lignocellulose. P. indianae efficiently hydrolyzed substrates such as corn stover and poplar to generate sugars, fermentation acids, and ethanol, which K. marxianus consumed while producing 2.4 g/L ethyl acetate. An engineered strain of K. marxianus was also able to produce 550 mg/L 2-phenylethanol and 150 mg/L isoamyl alcohol from P. indianae hydrolyzed lignocellulosic biomass. Despite the use of crude untreated plant material, production yields were comparable to optimized rich yeast media due to the use of all available carbon including organic acids, which formed up to 97% of free carbon in the fungal hydrolysate. This work demonstrates that anaerobic fungal pretreatment of lignocellulose can sustain the production of fine chemicals at high efficiency by partnering organisms with broad substrate versatility. 

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