Nutrient Potential of Tori Fruits (Luffa cylindrica L.): When Used as Substrate for Microbial Growth or Source of Natural Phytochemical Agent

Agro-industrial residues are rich in lignocellulosic and complex bioactive phytochemical compounds. It is a useful free-energy source of fermentation for the manufacture of various important industrial products – especially vitamins, enzymes, antioxidants, and antibiotics – whereas its phytochemicals exhibit antimicrobial activities. In this study, the potential of tori (Luffa cylindrica L.) fruit when used as a substrate for Bacillus subtilis (k1) growth or antimicrobial activity against selected human bacterial pathogens was assessed. Five Bacillus subtilis (k1) cultures of tori fruit, i.e. LBo [1.0 % tryptone, 0.5 % yeast extract, and 0.5 % NaCl, 1-L dH2O (pH 7.0–7.2)], LB1 (1/8 LBo medium in dH2O), LB2 (LB1 + 5 % peel’s powder), LB3 (LB1 + 5 % peeled-off fruits powder), and LB4 (LB1 + 5 % peels powder + 5 % peeled-off fruits powder), were maintained for 18 h. Maximum cell growth plus xylanase and pectinase activities were found in LB2, as well as total proteins, reducing sugars, and prolines in LB4 cultures (p ≤ 0.05). For phytochemical analysis and evaluation of their antimicrobial efficiency, extracts of dried peels and peeled-off fruits were extracted in ddH2O and 50% aqueous solutions (v/v) of acetone, ethanol, and methanol separately. Extraction yielded phenolics, flavonoids, steroids, and tannins in methanol extracts, whereas alkaloids and terpenoids in acetone extracts were observed significantly higher in peeled-off fruit (pulps) than peels respectively. Meanwhile, the highest zone of inhibition shown by methanol extraction from peeled-off fruits against Staphylococcus aureus (20.89 mm) and Bacillus subtilis (k1) (22.91 mm), which showed comparable inhibition as by the respective standard antibiotics at 27.76 and 28.85 mm. In conclusion, methanol extracts of tori showed good antimicrobial potential against selected bacterial species due to its specific-typed phytochemical extraction in a solvent.