In-Needle Pre-Column Derivatization for Amino Acid Quantification (iPDAQ) Using HPLC

Creating Single-Cell Protein-Producing Bacillus subtilis Mutants Using Chemical Mutagen and Amino Acid Inhibitors

Due to population growth and climate changes, there is a rising need for alternative food and protein sources to reduce protein scarcity and the environmental impact of food industries. Single-cell proteins (SCPs) have the potential to partially or fully substitute plant- and animal-derived dietary proteins. Bacillus subtilis is an appealing bacterium for SCP production because of its fast growth and ability to obtain high protein and essential amino acid (AA) content in its biomass. It is also capable of utilizing a wide range of substrates. B. subtilis attractiveness and efficiency can be further enhanced using mutagenesis. In this study, a novel approach to creating mutant strains with enhanced protein and AA content was experimentally validated. The method is based on the application of AA inhibitors for selective pressure to ensure the growth of mutants with enhanced protein and/or AA synthesis capacity. For AA inhibitors, three herbicides were used: glufosinate-ammonium (GA), L-methionine sulfoximine (MSO), and S-(2-aminoethyl)-L-cysteine (AEC). Initially, AA inhibitor doses for the complete inhibition of wild-type (WT) B. subtilis strain were determined. Then, B. subtilis was treated with EMS chemical mutagen and created mutants were cultivated on a medium containing inhibitory dose of AA inhibitors. Growing samples were selected, analyzed, and compared. The optimal inhibitory concentrations of herbicides for mutant selection were 0.05-0.4 M for GA, 0.01-0.05 M for MSO, and 0.2 M for AEC. The best-performing mutants were selected when using GA-improvement of 7.1 times higher biomass content, 1.5 times higher protein concentration, 1.2 times higher AA content, and 1.2 times higher essential AA index was achieved in comparison with WT B. subtilis. Enhanced mutants were also successfully selected when using MSO and AEC. This study demonstrates the potential of using AA inhibitors for the selection of mutants with improved protein and AA profiles.

Study on the solid-liquid equilibrium and thermodynamic model of the L-phenylalanine + L-tryptophan + water system

Amino acids hold significant importance in the diagnosis and treatment of various chronic diseases. Accurate solid-liquid equilibrium data are the key to drug synthesis and chemical production. However, the studies on the solid-liquid equilibrium of amino acids remain limited. In this work, the solid-liquid equilibrium of the L-tryptophan + L-phenylalanine + water ternary system under atmospheric pressure at temperatures of 278.15 K-318.15 K was explored via isothermal solution saturation. The isothermal equilibrium phase diagram of the ternary system was constructed. The obtained solid-liquid equilibrium data were correlated with a semi-empirical-model, yielding thermodynamic parameters pa, pb, pc, and k. Furthermore, the model can be used to effectively predict the solid-liquid equilibrium data of ternary systems at other temperatures, and the dY and dP are 0.005 and 4.34%, respectively. The solid-liquid equilibrium data and ternary equilibrium phase diagrams of the system were utilized for the separation and purification of an L-tryptophan and L-phenylalanine mixture. By employing thermodynamic models to calculate the relevant phase diagram data for mixtures with different proportions, effective separation and purification of the mixture could be achieved using the principles of variable temperature phase diagrams. These works are valuable for optimizing chemical processes and have practical implications in the field.