Inoculation with Jeotgalicoccus sp. improves nutritional quality and biological value of Eruca sativa by enhancing amino acid and phenolic metabolism and increasing mineral uptake, unsaturated fatty acids, vitamins, and antioxidants

Abstract

Plant growth-promoting bacteria (PGPB) are considered a promising tool for triggering the synthesis of bioactive compounds in plants and to produce healthy foods. This study aimed to demonstrate the impact of PGPB on the growth, accumulation of primary and secondary metabolites, biological activities, and nutritional qualities of Eruca sativa (arugula), a key leafy vegetable worldwide. To this end, Jeotgalicoccus sp. (JW0823), was isolated and identified by using partial 16S rDNA-based identification and phylogenetic analysis. The findings revealed that JW0823 significantly boosted plant biomass production by about 45% (P<0.05) and enhanced pigment contents by 47.5% to 83.8%. JW0823-treated plants showed remarkable improvements in their proximate composition and vitamin contents, with vitamin E levels increasing by 161.5%. JW0823 induced the accumulation of bioactive metabolites including antioxidants, vitamins, unsaturated fatty acids, and essential amino acids, thereby improving the nutritional qualities of treated plants. An increase in the amounts of amino acids was recorded, with isoleucine showing the highest increase of 270.2%. This was accompanied by increased activity of the key enzymes involved in amino acid biosynthesis, including glutamine synthase, dihydrodipicolinate synthase, cystathionine γ-synthase, and phenylalanine ammonia-lyase enzymes. Consequently, the total antioxidant and antidiabetic activities of the inoculated plants were enhanced. Additionally, JW0823 improved antimicrobial activity against several pathogenic microorganisms. Overall, the JW0823 treatment is a highly promising method for enhancing the health-promoting properties and biological characteristics of E. sativa, making it a valuable tool for improving the quality of this important leafy vegetable.

Keywords: antioxidant; arugula; biosynthetic enzymes; fatty acids; flavonoids; plant growth promoting bacteria.

Figure 1

Phylogenetic tree based on 16S rRNA gene sequences, constructed by the Maximum of likelihood method using MegaX application, showing the position of strain JW0823 among closest species available at GenBank.

Figure 2

Effect of JW0823 bacteria on the biomass and pigment contents of Eruca sativa represented by (A) the biomass (B) chlorophyll a, (C) chlorophyll b, (D) chlorophyll a+b, (E) Beta carotene, and (F) lycopene. Data are represented by means ± standard errors. Bars flagged with 1, or 2 asterisks indicate significant differences between JW0823 bacteria-treated and control groups at p<0.05, or p<0.01 respectively.

Figure 3

Effect of JW0823 bacteria on the proximate composition of Eruca sativa represented by (A) moisture, (B) total proteins, (C) total lipids, (D) crude fibers, (E) carbohydrates and (F) ash. Data are represented by means ± standard errors. Bars flagged with an asterisk indicate significant differences between JW0823 bacteria-treated and control groups at p<0.05.

Figure 4

Effect of JW0823 bacteria on the levels of (A) vitamins and (B) organic acids in Eruca sativa. Data are represented by means ± standard errors. Bars flagged with 1, 2, or 3 asterisks indicate significant differences between JW0823 bacteria-treated and control groups at p<0.05, p<0.01, or p<0.001, respectively.

Figure 5

Effect of JW0823 bacteria on the total antioxidant activities of Eruca sativa: (A) total phenolics, (B) total flavonoids, (C) FRAP, (D) ABTS and (E) DPPH. Data are represented by means ± standard errors. Bars flagged with an asterisk indicate significant differences between JW0823 bacteria-treated and control groups at p<0.05.

Figure 6

Effect of JW0823 bacteria on the antimicrobial activities of Eruca sativa. Data are represented by means ± standard errors. Bars flagged with 1 or 2 asterisks indicate significant differences between JW0823 bacteria-treated and control groups at p<0.05 or p<0.01, respectively.

Figure 7

Effect of JW0823 bacteria on the antidiabetic activities of Eruca sativa sprouts represented by (A) α- amylase inhibition activity (%), (B) α- glucosidase inhibition activity (%), and (C) glycemic index %. Data are represented by means ± standard errors. Bars flagged with an asterisk indicate significant differences between JW0823 bacteria-treated and control groups at p<0.05.