## 2 Materials and Methods  
### Plant Material and Growth Conditions for Sprouts  
Kale seeds (_Brassica oleracea_ L. var. _sabellica_ L.) were purchased in W. Legutko Breeding and Seed Company LLC Poland. Lupine seeds (_Lupinus luteus_ L. var. MISTER) were purchased in Malopolska Hodowla Roslin (Krakow, Poland). Both evaluated seeds were stored in the Department of Food Chemistry and Nutrition seeds collection, with appropriate voucher numbers: BOS/PP/PL1045 and LL/PP/PL1048, respectively.  
Kale and lupin seeds were immersed in commercially available mineral water (controls) or in such water with two different \(\gamma\)-PGA concentrations (0.01% and 0.05% for kale; 0.1% and 0.5% for lupin) for 30 min. Then, they were evenly distributed in the gutters of three EQMM Easy Green Microfarm sprouters, each with five gutters (i.e., five biological replicates). The chamber of the first germinator was filled with water, the second with lower concentrated solutions of \(\gamma\)-polyglutamic acid (0.1% for lupin; 0.01% for kale), and the third one with a solution of this acid at higher concentrations (0.5% for lupin; 0.05% for kale). The cultivation of lupine and kale sprouts was carried out independently. The kale sprouts were grown for 6, 7, or 8 days after seeding, at a temperature of 24 \(\pm\) 2 \({}^{\circ}\)C, in natural light conditions. They were watered 3 times per day with the same solutions. The procedure for lupine sprouts was analogous, with the difference being that the sprouts were harvested on days 6, 8, and 10. The selection of both \(\gamma\)-PGA concentrations and sprouting duration was based on estimated calculations [12] and prior optimization studies, focusing primarily on the appearance, growth, drying, and rotting of the sprouts. The \(\gamma\)-PGA concentrations were chosen based on their observed effects on seedling development, ensuring that they supported normal growth without causing excessive sprout elongation or structural abnormalities. The germination time was carefully selected to prevent overgrowth, which could lead to the sprouts becoming weaker, drying out, or becoming more susceptible to rotting. Extended sprouting periods can also create microgreens and favorable conditions for microbial contamination, which could compromise the quality and safety of the sprouts. Therefore, the chosen conditions were optimized to balance healthy sprout growth while minimizing potential negative effects such as desiccation or decay. For each of the treatments, three replicates were taken for analysis [35].  
The preparation of appropriate \(\gamma\)-PGA solutions is described briefly below. Bacillus licheniformis was isolated from organic soils and maintained in sterile glycerol (50%, \(w/v\)) at \(-80\)\({}^{\circ}\)C. The strain was confirmed using MS MALDI TOF spectrometry, by the direct transfer method. The medium used for culture growth and \(\gamma\)-polyglutamic production contained (per liter) glucose--60 g monosodium glutamate--25 g, citric acid--5 g, hydrated MgSO4--0.5 g, hydrated MnO4--0.1 g, K2 HPO4--1.0 g, hydrated CaCl2--0.2 g, and hydrated FeCl3--0.02 g [36]. The initial pH was adjusted to pH 6.8 \(\pm\) 0.1 with 1 M NaOH in 500 mL baffled flasks and incubated aerobically at 150 rpm and 37 \({}^{\circ}\)C for 48 h. The presence of \(\gamma\)-PGA in the culture broth was estimated by the most specific chemical precipitation method with saturated CuSO4. To obtain the pure fraction, we used a triple micro-ultra and nanofiltration method, using a preliminary 0.25 \(\upmu\)m filter, then 100 kDa and 200 Da filters [37]. The fraction used in the experiment consisted of a 4% mixture of \(\gamma\)-PGA polymers in the 100 kDa to 200 Da range.