## 1 Introduction
Lactic acid is a metabolite generated by lactic acid bacteria in the presence of carbohydrates, especially six-carbon sugars such as glucose or sucrose [20]. The most desired in commercial production are the enantiomers L(+) of lactic acid, which is primarily generated by homoffermatative lactic fermentation bacteria of the _Lactobacillus genus_[21]. Lactic acid has traditionally been employed in the preparation of meat, fruit, and vegetables due to its powerful preservation effect; however, lately, it has gained popularity in the cosmetic business [22]. Its distinctive action is to acidify the environment since a low pH prevents the growth of unwanted microflora in food and cosmetic items [23]. _Syzgium aromaticum_ L. belongs to the _Myrtaceae_ family, which includes more than 3000 species and about 150 genera, such as the myrtle, eucalyptus, clove, and guava families. A review of the literature showed the high biological activity of essential oils and extracts obtained from most _Myrtaceae_ species [24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34; 35; 36]. The oils and extracts from _Acca sellowiana_, _Blepharocalyx salicfolius_, _Calyptranthes lucida_, _C. pallens_, _Eugenia acapulcensis_, _E. bacopari_, _E. beaurepaireana_, _E. brasiliensis_, _E. chlorophylla_, _E. pluriflora_, _E. umbelliflora_, _E. stipitata ssp. sororia_, _E. uruguayensis_, and _E. uniflora_ were found to have antibacterial properties. This was because they contained phenolics (eugenol and eugenol acetate) and terpen (\(\beta\)-caryophyllene and \(\alpha\)-humulene). Antioxidant (_Campomonas xanthocarpa_, _E. involucrata_, _E. uniflora_, _P. cattleyanum_), antinociceptiveptive (_P. guajana, P. pohlianum, E. uniflora_), anti-inflammatory (_E. jamboiana, Psidium cattleyanum_), and analgesic (_P. guianense_) properties were also shown by some _Myrtaceae_ species. Extracts obtained from plants of the _Myrtaceae_ family (myrtle, eucalyptus, and clove) effectively inhibit the growth of Gram-negative and Gram-positive bacteria (_S. marcescens, P. aeruginosa, Streptococcus sanguinis, Streptococcus mitis, Fusobacterium nucleatum_, _Escherichia coli_, _Staphylococcus aureus_, _S. marcescens, P. aeruginosa, Corynebacterium bovis_, _Corynebacterium striatum_, and _Corynebacterium jeikeium_), which cause skin infections, tooth decay, and food spoilage. These results demonstrate the enormous potential of the _Myrtaceae_ family [24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36]. The buds of the clove tree yield two principal products: cloves (_S. aromaticum_ L.)--rich in essential oil--and eugenol (4-allyl-2-methoxyphenyl), the main ingredient of clove oil. Currently, cloves are used in both the spice industry and the traditional Indonesian cigarette market, the kretek. The essential oil extract is utilised for plasticising, anaesthetic, antibacterial, and organoleptic qualities, which are used in cosme, dentistry, and the agro-food industries [37, 38, 39, 34]. Because of its qualities, the oil has a wide range of uses, particularly in the pharmaceutical business (as a component in warming and analgesic ointments) and dentistry (as an ingredient in analgesic preparations, dental cavity fillings, mouth and gum rinses, and toothpaste) [34, 37, 40]. High antimicrobial and antioxidant activity classify eugenol as an absorption promoter [37, 38]. Eugenol also has a positive effect on the complexion of people with acne and psoriasis, which is why it is recommended in cosmetic formulas designed for acne skin care, as it reduces the appearance of lesions and accelerates the healing of existing ones [37, 38, 41, 42, 43, 44]. The presented research is related to the development of the most favourable process conditions for the fermentation of stems from _S. aromaticum_ L. using lactic acid bacteria (LAB) and beet molasses (which is a valuable source of six-carbon sugars) to obtain fermented plant extracts (FPEs).