## 1 Introduction  
In recent years, interest in \(\gamma\)-polyglutamic acid (\(\gamma\)-PGA) has increased due to its specific biochemical properties and potential for use in various fields [1]. \(\gamma\)-PGA is a biopolymer composed of D- and L-glutamic acid monomers, which are connected by amide bonds between \(\alpha\)-amino and \(\gamma\)-carboxyl groups [2]. The \(\gamma\) bond between glutamate units gives it resistance to proteases that break down \(\alpha\)-amine bonds. \(\gamma\)-PGA may exist in two forms: (i) soluble in water as a salt with cations or (ii) insoluble as a free acid [3]. Due to advantages such as the low cost of substrates for its synthesis, mild process conditions, and low impact on environmental pollution, the main method of producing \(\gamma\)-PGA is microbial fermentation [1; 4]. Bacteria producing \(\gamma\)-PGA are categorized into two groups based on the dependence of their metabolism on glutamic acid. The first group includes strains that require the presence of glutamic acid in the medium, so it should be supplemented with glutamate. The second group consists of glutamate-independent strains that use, for example, citric acid, appropriate amino acids, or glucose. By cultivating bacteria in appropriate combinations, it is possible to supervise the process and obtain \(\gamma\)-PGA with different molecular weights [2; 5]. The molecular weight of \(\gamma\)-PGA synthesized by microorganisms is in a wide range of 1-8000 kDa [4]. Apart from the type of bacteria, other factors, such as aeration of the solution in which this compound is synthesized, pH value, and process time, also influence the molecular weight of \(\gamma\)-PGA [6]. The different molecular weight values of \(\gamma\)-PGA influence the physicochemical properties of it and, consequently, its wide range of applications in various systems [1]. Numerous biochemical properties of \(\gamma\)-PGA, such as solubility in water, lack of toxicity and immunogenicity, edibility, water retention capacity, and biodegradability, as well as antioxidant and antimicrobial activity, determine its uniqueness [1; 2; 6; 7]. These properties make it possible to be used in the food, agricultural, cosmetic, and pharmaceutical industries and even in environmental engineering [2; 4]. Several studies indicate the multifunctional role of \(\gamma\)-PGA in both vegetative growth and reproductive success in plants, improving also the plant-microbe relationships. In rice cultivars, \(\gamma\)-PGA can enhance seed germination and sprouting by improving various physiological processes [8; 9; 10]. It may enhance enzymatic activity and enhance water absorption in seeds, leading to improved germination rates [11]. \(\gamma\)-PGA is known to improve root and shoot development, stimulating the production of growth hormones, such as auxins and cytokins, which play crucial roles during the vegetative stage. Research highlights \(\gamma\)-PGA's role in improving plants' resistance to abiotic stresses such as drought and salinity [12; 13]. It has been found to regulate osmotic pressure and promote the accumulation of stress-related metabolites [13]. Its use has been linked to increased production of phytoalexins and other defense compounds, improving resistance against pathogens [14]. Some studies have reported increased fruit and flower yields when \(\gamma\)-PGA is applied during the reproductive phase [15]. This can be attributed to its effects on nutrient uptake and enhancement of floral development, significantly increasing plant height, chlorophyll content, above-ground biomass, and underground biomass [16]. \(\gamma\)-PGA has garnered attention for its diverse applications in functional food systems, offering numerous benefits that enhance both the quality and nutritional value of food products [17]. One of its most notable attributes is its ability to improve the bioavailability of nutrients and bioactive compounds.