Light quality and duration profoundly influence the growth and productivity of plant species. This study investigated the effects of a blue–red LED light combination, known to induce flowering, on the physiological state and content of biologically active substances in catmint (Nepeta nuda L.) grown under controlled in vitro conditions. White light (W) was used as a control and compared with two blue–red intensities: BR (high-intensity blue–red light) and BRS (low-intensity blue–red light or “BR with shadow”). BR-treated plants showed increased leaf area, mesophyll thickness, biomass and starch content but reduced levels of plastid pigments. BR also modified the oxidative state of plants by inducing lipid peroxidation while simultaneously activating ROS scavenging mechanisms and enhancing phenolic antioxidants. Interestingly, BR decreased the accumulation of the Nepeta sp.-specific iridoid, nepetalactone. These effects appear to be regulated by the phytohormones auxin, abscisic acid and jasmonates. BRS treatment produced effects similar to the W control but led to increased plant height and reduced leaf area and thickness. Both BR and BRS regimes induced the accumulation of proteins and amino acids. We conclude that blue–red light can enhance the survival capacity of micropropagated N. nuda during subsequent soil adaptation, suggesting that similar light pre-treatment could improve plant performance under stress conditions.

Baker’s yeast is a key starting material for producing extracts with diverse compositions and applications. This study investigates the effect of pulsed electric field (PEF) pretreatment, which induces irreversible electropermeabilization, on the enzymatic hydrolysis of yeast. Cell suspensions were exposed to monopolar rectangular pulses in a continuous flow system followed by 4 h of incubation with Alcalase at concentrations of 0.2% and 0.5%. PEF pretreatment significantly improved enzymatic hydrolysis, with maximum intracellular content recovery under electrical conditions resulting in outlet temperatures of 56–58 °C. The released protein reached 163.7 ± 13 mg per gram of dry cell weight (DCW). SDS-PAGE analysis showed that the extracts predominantly contained peptides with molecular masses below 4.7 kDa. The phenolic content was comparable to that of cell lysates obtained after mechanical disruption. The free α-amino nitrogen content and total antioxidant activity reached 218.2 ± 26 mg/gDCW and 53.4 ± 4.6 mg TE/gDCW, respectively, representing 3.2-fold and 2.65-fold increases compared to cell lysates. The hydrolysates from PEF-pretreated cells demonstrated a positive effect on the proliferation of the human keratinocyte cell line HaCat. The obtained data lead to the conclusion that PEF pretreatment is a promising approach to enhance the production of yeast hydrolysates with various applications.

Spent brewer’s yeast, a major by-product of the brewing industry, is a valuable source of bioactive compounds. The main technological limitation for their recovery is the rigid yeast cell wall, while the high nucleic acid content may restrict the direct use of yeast-derived extracts for human nutrition. In this study, pulsed electric field (PEF) treatment, applied alone or in combination with enzymatic hydrolysis, was investigated for the production of yeast-derived extracts with different compositions. PEF treatment performed in continuous-flow mode resulted in more than 98% of cells with irreversibly permeabilized membranes and enabled the rapid and selective release of low-molecular-weight intracellular compounds during subsequent incubation of the cells in water. Within 4 h, approximately 61% of total antioxidant activity, 65% of glutathione, and around 80% of free α-amino nitrogen and B-group vitamins were recovered at different rates, while the aqueous extracts were characterized by low purine nucleotide content. Electropermeabilized cells exhibited high sensitivity to enzymatic hydrolysis. After 6 h of incubation with 0.2% (v/v) Alcalase, the obtained hydrolysates contained 254 ± 17 mg/g DCW of protein, mostly in the form of peptides, 148.2 ± 17.3 mg/g DCW of free α-amino nitrogen, and a total phenolic content of 16.7 ± 1.9 mg GAE/g DCW. The maximal antioxidant activity (62.7 ± 9.3 mg TE/g DCW) was reached after 4 h of incubation, corresponding to a 2.7-fold increase compared with cell lysates. Overall, PEF treatment, applied alone or in combination with enzymatic hydrolysis, provides an efficient and mild approach for the production of yeast-derived extracts with tailored compositions and potential applications in the food, pharmaceutical, and cosmetic industries.

The application of series of high intensity electric pulses to a yeast suspension provoked a considerable release of some cytoplasmic proteins, glutathione reductase, 3-phosphoglycerate kinase and alcohol dehydrogenase. A maximal yield was achieved 3–8 h after pulsation. The electro-induced protein efflux was accelerated by pretreatment with the reducing agent dithiothreitol and showed a strong dependence on the growth phase and the presence of monovalent ions in the post-pulse incubation medium. The results obtained for two strains of Saccharomyces cerevisiae, PV3 (diploid) and Y47 (wild haploid), showed that electropulsation can be used for the effective extraction of cytoplasmic proteins with a preserved functional activity.