Homofermentative Lactobacilli isolated from organic sources exhibit potential ability of lactic acid production

There has been an increasing interest in recent years in lactic acid bacteria that are derived from organic sources for lactic acid production. This research article presents the isolation and identification of homofermentative lactic acid bacteria from various novel organic sources, followed by qualitative and quantitative analyses of lactic acid produced. A total of 32 isolates were identified initially from various sources, such as curd (C1, C2), probiotics (P1, P2, and P3), silage (Si1 and Si2), soil samples (S1, S2, and S3), vermicompost (V1 and V2), and Farmyard manure. Biochemical tests such as Gram's staining, catalase test, and oxidase test were conducted for preliminary identification of lactic acid bacteria using De Man, Rogosa, and Sharpe agar (MRS) media. Through selection and identification, based on colony morphology and biochemical characteristics, 18 isolates were identified as lactic acid bacteria. The subsequent analysis included a tube test, screening for organic acid production, and homofermentative screening using homofermentative-heterofermentative differential (HHD) medium for qualitative analysis of lactic acid. The results revealed that 9 out of 18 selected strains were homofermentative and had promising potential for the production of lactic acid. Furthermore, six isolates (P1-1, S1-3, C2-1, V2-3, P2-1, and C1-1) from all of the nine positive strains were subjected to pH testing (0, 24, 48, and 72 h) and titrimetric assay for estimation of % crude lactic acid present. The presence of lactic acid was confirmed using thin-layer chromatography (TLC). L (+)-Lactic acid was quantified using a K-LATE enzymatic assay kit, for the best three isolates (P1-1, S1-3, C2-1). Finally, the strains were subjected to 16SrRNA sequencing and were identified as Lactobacilli. Based on the findings of the study, it could be concluded that homofermentative lactic acid bacteria with significant LA-producing ability can be obtained from different organic sources and may prove to be useful in the successful production of lactic acid for biotechnological applications.

A photonic crystal fiber-based fluorescence sensor for simultaneous and sensitive detection of lactic acid enantiomers

A photonic crystal fiber (PCF)–based fluorescence sensor is developed for rapid and sensitive detection of lactic acid (LA) enantiomers in serum samples. The sensor is fabricated by chemical binding dual enzymes on the inner surface of the PCF with numerous pore structures and a large specific surface area, which is suitable to be utilized as an enzymatic reaction carrier. To achieve simultaneous detection of l-LA and d-LA, the PCF with an aldehyde-activated surface is cut into two separate pieces, one of which is coated with l-LDH/GPT enzymes and the other with d-LDH/GPT enzymes. By being connected and carefully aligned to each other by a suitable sleeve tube connector, the responses of both l-LA and d-LA sensors are determined by laser-induced flourescence (LIF) detection. With the aid of enzyme-linked catalytic reactions, the proposed PCF sensor can greatly improve the sensitivity and analysis speed for the detection of LA enantiomers. The PCF sensor exhibits a low limit of detection of 9.5 μM and 0.8 μM, and a wide linear range of 25–2000 μM and 2–400 μM for l-LA and d-LA, respectively. The sensor has been successfully applied to accurate determination of LA enantiomers in human serum with satisfactory reproducibility and stability. It is indicated that the present PCF sensors would be used as an attractive analytical platform for quantitative detection of trace-amount LA enantiomers in real biological samples, and thus would play a role in disease diagnosis and clinical monitoring in point-of-care testing.

Enantioseparation using carboxymethyl-6-(4-methoxybenzylamino)-β-cyclodextrin as a chiral selector by capillary electrophoresis and molecular modeling study of the recognition mechanism

In this study, carboxymethyl-6-(4-methoxybenzylamino)-β-cyclodextrin (CMCDPN) was synthesized for the first time and managed to be used as a chiral selector to enantioseparate 13 kinds of chiral drugs by capillary electrophoresis.

Chromatographic Enantioseparations in Achiral Environments: Myth or Truth?

Direct chromatographic enantioseparations are among the most important practical tasks of chromatography. The accepted rules and concepts of stereochemistry anticipated one type of chromatographic systems applicable only to such enantioseparations consisting either of chiral stationary phase, or chiral selector present in mobile phase. In such a model of chromatographic system, both racemic and non-racemic mixtures could be enantioseparated. Over the years, however, reports on successful chiral enantioseparations in non-chiral chromatographic systems have cumulated as well. To adapt the initial model to novel experimental evidence, an assumption had to be added stating that these were only non-racemic mixtures (and not racemic ones), which could be enantioseparated in achiral chromatographic systems, by granting them an inevitable chirality from the enantiomeric excess of a more abundant enantiomer. There still exists an overlooked portion of experimental evidence for successful enantioseparations of racemic mixtures in the non-chiral chromatographic systems, which cannot be explained by the accepted model. Facing this incompatibility between the model and practical results, we reflect on how to reconcile these two by questioning the possibility of pinpointing a true racemate with the help of our imperfect analytical tools.

Condensation oscillations in the peptidization of phenylglycine

In earlier studies, we showed that certain low-molecular-weight carboxylic acids (profens, amino acids, hydroxy acids) can undergo spontaneous in vitro chiral conversion accompanied by condensation to from oligomers, and we proposed two simple models to describe these processes. Here, we present the results of investigations using non-chiral high-performance liquid chromatography with diode array detector (HPLC-DAD) and mass spectrometry (MS) on the dynamics of peptidization of S-, R-, and rac-phenylglycine dissolved in 70% aqueous ethanol and stored for times up to one year. The experimental results demonstrate that peptidization of phenylglycine can occur in an oscillatory fashion. We also describe, and carry out simulations with, three models that capture key aspects of the oscillatory condensation and chiral conversion processes.