A mathematical model for the growth kinetics and synthesis of phenolics in oregano (Origanum vulgare) shoot cultures inoculated with Pseudomonas species

Autoinduction AND Gate Inhibits Cell Lysis to Enhance Protein Production in Bacillus subtilis Controlled by Population Density and Cell Physiological State

The extracellular protease-deficient strain Bacillus subtilis WB600 is commonly used as a chassis cell for the production of industrial proteins. However, B. subtilis WB600 exhibits an increased susceptibility to cell lysis and a reduction in biomass. Inhibition of cell lysis by knocking out lytic genes will impair physiological function. Here, we dynamically inhibited cell lysis in B. subtilis WB600 to balance the impairment of physiological function with the accumulation of biomass. First, the inducible protein degradation systems (IPDSs) were constructed and used to investigate the effects of inhibiting cell lysis on biomass, cell morphology, and protein production at different times (using pullulanase as a test). The highest pullulanase activity was obtained at 20 h of inhibiting cell lysis, 184.8 U/mL, which was 44% higher than the activity of B. subtilis WB600. Then, to avoid addition of inducers, we introduced orthogonal quorum sensing and constructed autoinduction protein degradation systems (AIPDSs). The optimized AIPDS showed similar pullulanase activity to the optimal IPDS (20 h), 181.3 U/mL. Next, we constructed dual-signal input autoinduction protein degradation systems (DSI-AIPDSs) via AND gate to further address two deficiencies of AIPDS, one-time activation and damage to new cells. These DSI-AIPDSs were controlled by quorum sensing and stationary phase promoters that respond to population density and single-cell physiological state, respectively. Finally, the OD₆₀₀ and pullulanase activity of the strain with optimal DSI-AIPDS were 51% and 115% higher than those of B. subtilis WB600 in pullulanase production, respectively. We provided a B. subtilis chassis strain with considerable potential for biomass accumulation and enhanced protein production.

Enhancing scleroglucan production by Sclerotium rolfsii WSH-G01 through a pH-shift strategy based on kinetic analysis

As a stable microbial polysaccharide, scleroglucan has extensive application in the food, medicine, and cosmetics industries. However, its large-scale industrial application is limited by its high production cost, low yield, long production time, etc. This study aims to enhance scleroglucan production by Sclerotium rolfsii WSH-G01. Based on the analysis of batch fermentation kinetics parameters, a pH-shift strategy was adopted. Through systematic kinetics analysis, a 32.4 g/L scleroglucan was accomplished. The kinetic model of the pH-shift batch fermentation process was established using a logistic equation, Luedeking-Piret equation, and a Luedeking-Piret-like equation. As decreased glucose concentration could cause decreased scleroglucan synthesis rates during the batch fermentation process, 30 g/L glucose was fed in the later phase of fermentation. As a result, scleroglucan production increased to 42 g/L, with a productivity of 0.5 g/L·h. Thus, the pH-shift strategy and feeding approach could be useful for industrial scleroglucan production.

Model-based temperature control for improving lactic acid production from glycerol

To maximize the final lactic acid productivity and concentration, temperature control was optimized using a mathematical modelling approach. A kinetic model, including cell growth, product formation and substrate consumption equations, was proposed to describe the lactic acid production process by Escherichia coli AC-521 with glycerol as the substrate. By constructing four functions, the temperature effect was introduced on the fermentation process, where four parameters (X_max, μ_max, Y_ps and β) were observed to be significantly affected by the temperature. For the convenience of application, the temperature control strategies were simplified by dividing the whole fermentation process into several units. In each unit, the temperature was controlled constantly. Based on the model, the optimal temperature for each unit was determined to maximize the final lactate productivity. This temperature control strategy can be effectively applied in batch and fed-batch cultures, and the verified experimental evaluation showed a good correlation with the model data. Under improved temperature control conditions, a maximal lactic acid concentration of 90.4 g L⁻¹ was obtained after 80 h of fed-batch fermentation, giving a productivity of 1.13 g L⁻¹ h⁻¹, which is 1.2 times more than that in the conventional constant temperature during the cultivation course.

With model-based temperature control, yield of lactic acid obtained was higher than that obtained in the conventional process with a constant temperature.

The isolation, structural characterization, and anticancer activity from the aerial parts of Cymbopogon flexuosus

This study investigated bioactive secondary metabolites from the aerial parts of Cymbopogon flexuosus (CF). Total phenolic and total flavonoid contents, the antioxidant activities including 2, 2'-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS⁺ ) and 2, 2'-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging systems, and cytotoxic effects were determined. 1, 3-O-di-E-caffeoylglycerol (SA3) and 1-O-p-coumaroyl-3-O-caffeoylglycerol (SA4) were firstly isolated from an ethanol extract of CF. Their chemical structures were elucidated by extensive spectroscopic analyses, including MS and NMR spectra as well as by comparison to the data reported in the literature. DPPH and ABTS⁺ radical scavenging tests showed that the highest antioxidant potent was detected for compound SA3 with IC₅₀ of 4.42 ± 0.18 and 21.84 ± 0.22 µg/ml, respectively. The compound SA3 stimulated the apoptotic factors of caspase-3, bax, and bcl-2 in HepG2 and caspase-3, caspase-9, P53 in A549. PRACTICAL APPLICATIONS: CF has been widely used as both a herbal drink and as a spice in diets. In the food processing industry, CF was used to process candy. In addition, it is used for the treatment of sore throat, cough, skin diseases, and other diseases in traditional oriental medicine. Recently, in Vietnam, CF has also been used to treat liver and lung cancer and consumed daily to process many dishes.

Evaluation of genotoxic and cytotoxic effects of hydroalcoholic extract of Euphorbia tirucalli (Euphorbiaceae) in cell cultures of human leukocytes

Euphorbia tirucalli (L.), commonly known as aveloz, has been indiscriminately used in popular medicine to treat various illnesses. However, some components can have devastating consequences. Injury to a cell's genetic material can cause mutations, cancer, and cell death. Our main goal in this work was to evaluate the genotoxic and cytotoxic effects of E. tirucalli extract on human leukocytes. For this purpose, we performed a phytochemical analysis to evaluate the plant's components. In the second step, we treated cultured human leukocytes with different concentrations of the dry extract of the plant and then evaluated the oxidative and genotoxic profiles of these leukocytes. We found that at 1% and 10% concentrations, the aveloz extract acted as a genotoxic agent that could damage DNA and increase oxidative damage. We conclude that despite its popular use, aveloz can act as a genotoxic agent, especially when it contains phorbol ester. Aveloz's indiscriminate use might actually promote tumors and therefore carry a considerable genetic risk for its users.

Characterization of bioactive compounds and ameliorative effects of Ceratonia siliqua leaf extract against CCl₄ induced hepatic oxidative damage and renal failure in rats

Ceratonia siliqua is a typical Mediterranean plant, mainly used in food and Tunisian traditional folk medicine. Among the tested extracts, the ethyl acetate fraction (EACs) exhibited the highest total phenolic and flavonoids content. The antioxidant activity in vitro systems showed a more significant potent free radical scavenging activity of this extract than other analysis fractions. The HPLC finger print of EACs active extract showed the presence of six phenolic compounds. The in vivo results showed that oral administration of CCl(4) enhanced levels of hepatic and renal markers (ALT, AST, ALP, LDH, γ-GT, urea and creatinine) in the serum of experimental animals. It also increased the oxidative stress markers resulting in increased levels of the lipid peroxidation with a concomitant decrease in the levels of enzymatic antioxidants (SOD, CAT, GPx) in both liver and kidney. The pre-treatment of experimental rats with 250 mg/kg (BW) of the EACs, by intraperitoneal injection for 8 days, prevented CCl(4) induced disorders in the levels of hepatic and kidney markers. The biochemical changes were in accordance with histopathological observations suggesting a marked hepatoprotective and nephroprotective effect of the EACs extract.

The antioxidant and cytotoxic activities of Sonchus oleraceus L. extracts

This study investigated in vitro antioxidant activity of Sonchus oleraceus L. by extraction solvent, which were examined by reducing power, hydroxyl radical-scavenging activity(HRSA) and 1, 1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assays. 70% MeOH extract had the greatest reducing power while EtOH extract had the greatest HRSA. The antioxidant activity of S. oleraceus extracts was concentration dependent and its IC₅₀ values ranged from 47.1 to 210.5 µg/ml and IC₅₀ of 70% MeOH, boiling water and 70% EtOH extracts were 47.1, 52.7 and 56.5 µg/ml, respectively. 70% MeOH extract of S. oleraceus contained the greatest amount of both phenolic and flavonoid contents. The extracts tested had greater nitrite scavenging effects at lower pH conditions. The cytotoxic activity showed that EtOH extract had the best activity against the growth of stomach cancer cell. These results suggest that S. oleraceus extract could be used as a potential source of natural antioxidants.

Chemical composition andin vitroantifungal and antioxidant activity of the essential oil and methanolic extract ofTeucrium sauvageiLe Houerou

The chemical composition and the in vitro antifungal and antioxidant activity of the essential oil and the methanolic leaf extracts of Teucrium sauvagei Le Houerou, an endemic medicinal plant growing in Tunisia, have been studied. More than 35 constituents having an abundance >or=0.2% were identified in the oil. beta-Eudesmol, T-cadinol, alpha-thujene, gamma-cadinene, and sabinene were the prevalent constituents. Results of the antifungal activity tests indicated that the methanolic extract inhibited the in vitro growth of seven dermatophytes, whereas the essential oil showed average inhibition against only three dermatophytes. In vitro antioxidant properties of the essential oil and the methanolic extract were determined by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid)) assays and compared to those of the synthetic antioxidant Trolox. Due to their antifungal and antioxidant properties, the essential oil and the methanolic extract of T. sauvagei may be of use as natural preservative ingredients in food and/or pharmaceutical industries.

In vitro antimicrobial and antioxidant activities of the essential oils and various extracts of Thymus eigii M. Zohary et P.H. Davis

This study was designed to examine the in vitro antimicrobial and antioxidant activities of the essential oil and various extracts obtained from aerial parts of Thymus eigii. The essential oil was particularly found to possess stronger antimicrobial activity, whereas other nonpolar extracts and subfractions showed moderate activity and polar extracts remained almost inactive. GC-MS analysis of the oil resulted in the identification of 39 compounds, representing 93.7% of the oil; thymol (30.6%), carvacrol (26.1%), and p-cymene (13.0%) were the main components. The samples were also subjected to a screening for their possible antioxidant activity by using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and beta-carotene-linoleic acid assays. In the former case, the polar subfraction of the methanol extract was found to be superior to all extracts tested, only 16.8 microg/mL of which provided 50% inhibition, whereas all extracts, particularly the polar ones, seem to inhibit the oxidation of linoleic acid in the latter case. These data were further supported by total phenolics analysis, indicating that the antioxidative potential of the extracts was closely related to their phenolic constituents.