Common nettle as substrate for the growth of Lacticaseibacillus sp. and Ligilactobacillus sp.

Abstract

Common nettle (Urtica dioica) is widely spread medicinal plant growing in Europe. It is used as food, herbal tea or extract in dietary supplements. Significant amount of common nettle herb residues remains during standard herb processing in herbal tea production – due to grounding and fragility of dried common nettle’s leaf. These residues are currently underexploited and are considered waste, but could be used for extraction. Dried or liquid extracts of pharmacopoeial-level quality common nettle are used in iron supplementation, in treatments of rheumatoid diseases, hyperthensia or hyperglycemic disorders. Green solvents, water and ethanol are preferable for sustainable extractions and food and health related applications. Additionally, these solvents favour extraction of polar compounds like glycosides which could be metabolized by microorganisms. Water extracts do not harm microorganisms and are used as such in fermentation while ethanol have to be removed before fermentations. In our work, we studied water extraction of common nettle herb and its residues and tested these extracts as substrates for the growth of Ligilactobacillus salivarius and Lacticaseibacillus rhamnosus, bacteria with probiotic potential. Antioxidant activity (DPPH and ABTS methods) and growth of L. salivarius and L. rhamnosus were common nettle’s extracts obtained under different conditions. The extracts obtained from residues showed comparable or even superior antioxidant activity to extracts obtained from standard herb. Common nettle extracts without carbon or nitrogen supplementation were poor substrates for the growth of L. salivarius and L. rhamnosus, while supplementation with broth in low percentages resulted in growth stimulation above control. Findings suggest that common nettle herb residues could be valorised in food chain avoiding landfill disposal and wasting of this valuable resource.

Kopriva (Urtica dioica) je široko rasprostranjena biljka koja raste širom Evrope. Koristi se za ishranu, kao čaj ili u formi ekstrakta u dijetetskim suplementima. Tokom prerade herbe koprive i pakovanja za primenu u formi čajeva nastaje značajna količina otpada – izdrobljene herbe koprive. Ovaj otpad se za sada ne koristi i smatra se otpadom, ali bi se mogao koristiti za ekstrakcije. Suvi i tečni ekstrakti koprive farmakopejskog kvaliteta se koriste za tretmanu anemija, reumatoidnih bolesti, hipertenzije i hiperglikemijskih poremećaja. Zeleni rastvarači, voda i etanol su najpogodniji za dobijanje ekstrakata na održiv način za prehrambene i farmaceutske primene. Takođe, ovi rastvarači pogoduju ekstrakciji polarnih jedinjenja kao što su glikozidi koje mogu da fermentišu mikroorganizmi. Vodeni ekstrakti se mogu koristiti bez tretmana, jer ne utiču negativno na rast mikroorganizama, dok je iz etanolnih ekstrakata neophodno ukloniti etanol pre fermentacije. U radu smo proučavali vodenu ekstrakciju herbe koprive i otpada dobijenog preradom herbe. Testirali smo ekstrakte kao supstrate za rast Ligilactobacillus salivarius i Lacticaseibacillus rhamnosus, bakterija sa probiotskim potencijalom i antioksidantnu aktivnost ekstrakata (DPPH i ABTS metode). Antioksidantna aktivnost i rast L. salivarius i L. rhamnosus su ispitivani u ektraktima koprive dobijenim pod različitim uslovima. Ekstrakti dobijeni iz otpadna herbe koprive su pokazali sličnu ili čak bolju antioksidativnu aktivnost u odnosu na ekstrakte standardno korišćene herbe. Ekstrakti koprive bez dopune izvorima ugljenika ili azota su bili loš supstrat za rast L. salivarius i L. rhamnosus, dok su ekstrakti obogaćeni bujonom u niskom procentu pokazali rast bolji od kontrolnog uzorka. Rezultati rada ukazuju na potencijal otpada iz prerade koprive za primenu u prehrambenoj industriji čime bi se izbeglo odlaganje na deponije i bacanje ovog vrednog resursa.