Effects of γ-polyglutamic acid on grassland sandy soil properties and plant functional traits exposed to drought stress.

The current study provides field experimental data that support the use of γ-polyglutamic acid (γ-PGA) in drought stress and proposes its application in grassland management. We hypothesized that water treatment combined with PGA application to sandy soil would reduce drought stress in grasslands more effectively than watering alone. A randomized block design was used, with three replicate watering blocks (no watering, weekly watering, and monthly watering) and PGA treatments at four different concentrations (0%, 0.3%, 1%, and 2% PGA). The results showed that PGA acts as a biostimulant, alleviating the effects of stress in plants by: (1) increasing the availability of ions, especially K+, Zn2+, Mn2+, Fe2+/3+, Ca2+, and Mg2+, as well as N-NH4+, and N-NO3-, (2) elongating plant roots, (3) increasing the aboveground biomass, (4) improving the resprouting capacity of the dominant grass Nardus stricta, and (5) improving the regeneration of dicotyledons. In the case of meadows on sandy soils, the use of low PGA concentrations (0.3% or 1%) was the most beneficial for the availability of macro- and microelements and improving the functional traits of plants. Irrigation had a greater effect than using PGA only for the dicotyledon to monocotyledon ratio.

Basic Chemical Composition, Antioxidant Activity and Selected Polyphenolic Compounds Profile in Garlic Leaves and Bulbs Collected at Various Stages of Development.

Garlic is commonly used as vegetable or spice and as a herb in folklore as well as traditional medicine in many countries. The current study aimed to compare the chemical composition, antioxidant activity, and the content of selected polyphenolic compounds in cloves as well as leaves of winter garlic plants of the Harnas and Ornak cultivars, which are of Polish origin. Garlic was grown from cloves for three years (2018-2020) in the experimental field of the University of Agriculture in Krakow, Poland. The research material was harvested on three dates: May; June, unripe garlic plants; and in July, the plant at full maturity. The content of vitamin C in the fresh material was determined. The proximate analysis was determined in the freeze-dried plants of garlic, and the total carbohydrate content was calculated. The antioxidant activity and the content of selected polyphenolic compounds were also determined. Garlic cloves showed a higher content of dry matter, and total carbohydrates than the leaves of garlic plants. On the other hand, in the leaves, a significantly higher content of protein, total fat and ash were observed. Additionally, garlic leaves were characterised by a higher content of vitamin C, total polyphenols, and a higher antioxidant activity than garlic cloves. The leaves of young garlic plants from the May harvest were distinguished by a higher content of these compounds. The dominant phenolic compounds were catechin and epicatechin. The leaves of young plants can be a valuable source of bioactive substances, especially in early spring.

Hydrocarbon Degradation and Microbial Survival Improvement in Response to γ-Polyglutamic Acid Application.

To improve the environmental sustainability of cleanup activities of contaminated sites there is a need to develop technologies that minimize soil and habitat disturbances. Cleanup technologies, such as bioremediation, are based on biological products and processes, and they are important for the future of our planet. We studied the potential of γ-poly glutamic acid (PGA) as a natural component of biofilm produced by Bacillus sp. to be used for the decomposition of petroleum products, such as heavy naphtha (N), lubricating oil (O), and grease (G). The study aimed to assess the impact of the use of different concentrations of PGA on the degradation process of various fractions of petroleum hydrocarbons (PH) and its effect on bacterial population growth in harsh conditions of PH contamination. In laboratory conditions, four treatments of PGA with each of the petroleum products (N, O, and G) were tested: PGA0 (reference), PGA1 (1% PGA), PGA1B (1% PGA with Bacillus licheniformis), and PGA10 (10% PGA). After 7, 28, 56, and 112 days of the experiment, the percentage yield extraction, hydrocarbon mass loss, geochemical ratios, pH, electrical conductivity, and microorganisms survival were determined. We observed an increase in PH removal, reflected as a higher amount of extraction yield (growing with time and reaching about 11% in G) and loss of hydrocarbon mass (about 4% in O and G) in all treatments of the PGA compared to the reference. The positive degradation impact was intensive until around day 60. The PH removal stimulation by PGA was also reflected by changes in the values of geochemical ratios, which indicated that the highest rate of degradation was at the initial stage of the process. In general, for the stimulation of PH removal, using a lower (1%) concentration of PGA resulted in better performance than a higher concentration (10%). The PH removal facilitated by PGA is related to the anionic homopoliamid structure of the molecule and its action as a surfactant, which leads to the formation of micelles and the gradual release of PH absorbed in the zeolite carrier. Moreover, the protective properties of PGA against the extinction of bacteria under high concentrations of PH were identified. Generally, the γ-PGA biopolymer helps to degrade the hydrocarbon pollutants and stabilize the environment suitable for microbial degraders development.

Thermal properties and free radicals generation in starch isolated from pumpkin fruits.

The selected thermal and rheological properties of pumpkin starches were compared with values evaluated for corn and potato starch. The pumpkin starches had lower pasting temperatures (by near 3°C and 24°C than potato or corn starch respectively), the peak viscosity (nearly 2300mPas lower than potato starch) and higher final viscosities (by 80-120mPas than those for potato starch and by 1700mPas in relation to corn starch). The thermal profile of pumpkin starches examined by the DSC method were quite similar to those of potato starch but lower than those of corn. The retrogradation degree of pumpkin starch was lower by 5-26% than that for corn or potato starches. The thermal treatment of starches led to the formation of radicals. Pumpkin starches were less susceptible to the formation of radicals than potato starch and had less about 0.3-1.3×1015radicals/g than potato starch.