(614g) Antibacterial Activity of AGRO-Industrial Wastes and Common Plants Extracts for Health and Industrial Applications – Towards Circular Bioeconomy and Sustainability

Plants are an outstanding source of natural products for human beings and are used for various purposes. In recent years, research has been sought to determine the phytochemicals that have antimicrobial and antioxidant action for specific uses within areas including pharmaceuticals, cosmetics, bioremediation, animal feed and aquaculture [1]. Plant extracts are ecoming an important material for health, industrial and environmental applications, due to their content in bioactive compounds such as flavonoids, carotenoids, alkaloids, tannins and terpenoids, which have antimicrobial and antioxidant properties [2]. The bioactive components of plant extracts are terpenoids, alkaloids and phenolic compounds, they can interact with the enzymes and proteins of the microbial cell wall membrane that disperses the flow of protons out of the cell, that causes cell death. Chemical compounds in plant extracts can also inhibit enzymes that cause amino acid biosynthesis [3]. They can alter the structure or modify the permeability of the mitochondria of microorganisms [4].

Plants are used in food industry generating a great volume of residues, which currently are not part of the value chain, in the market a percentage of food is uneaten, and do not have and appropriate final disposal causing environmental impact [5]. Food and agro- industrial waste such as peels, leaves, bark, roots, seeds, husks, hulls, straw are used as renewable raw material since it contains chemical compounds [6]. This approach leads to food waste biorefinery and Circular Bioeconomy promoting local, regional and global sustainable development [7].

In this work, the antimicrobial activity of the some agricultural wastes was evaluated e.g. avocado (Musa Americana) seeds, cocoa (Theobroma cacao) shells, mangosteen (Garcinia mangostana) rinds, banana (Musa paradisiaca) peels, miracle fruit (Synsepalum dulcificum) shells; against bacteria Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa. The commonly used plants analyzed in this research had antibacterial activity against Vibrio parahaemolyticus. They were guava leaf (Psidium guajava), Cananga odorata flowers, eucalyptus leaves (Eucalyptus globulus), lemon verbena leaf (Cymbopogon citratus), Baccharis latifolia leaves, basil leaves (Ocimum basilicum). Samples were dried and sieved to a particle size of less than 250 microns. The extraction process was performed in a Soxhlet equipment using distilled water, 70% ethanol and 70% methanol, the extraction was performed for 4 hours. For agricultural waste, only water and 70% ethanol solvents were used. Extracts were frozen at -20°C before lyophilization [8].

Antibacterial activity determination was performed by the diffusion method, using 7 mm filter paper discs (duplicate). The lyophilized plant extracts were dissolved in distilled water, ethanol or methanol at a concentration of 200 mg/mL, the discs were impregnated with the plant extract solution and dried at 40 °C. Discs with distilled water, ethanol, methanol are the negative control in each extract and commercial antibiotics of the BD Sensidisco brand are used at 30 µg tetracycline per disc or 10 ug gentamicin as positive control. The diluted extracts were applied to the filter paper discs and then placed in Petri dishes with Mueller Hinton agar containing the bacteria to be tested. They were then incubated at 37 °C for 24 h and the diameter of the zone of inhibition was measured [9].

The results showed that for agricultural residues, a greater amount of lyophilized matter was obtained in the aqueous extract of mangosteen with an extraction yield of 21.23%, with the ethanol solvent a yield percentage was also identified that does not exceed The 12%. In the antibacterial activity tests. The results of agricultural residue extracts revealed that they have different degrees of bacterial inhibition. The results were expressed based on the diameter of the growth inhibition zone in millimeters. The data showed that the extracts at a concentration of 100 mg/ml had an inhibitory activity against S. aureus in the case of moringa cotyledon, mangosteen bark, avocado seed. Banana peel and cocoa pod extracts did not show antimicrobial activity against the bacterial strains tested. In the case of mangosteen rind, the aqueous and ethanolic extract had a moderate antibacterial activity against this bacterium in a similar range. Avocado seed had high activity against S. aureus with an inhibition halo diameter of (22.7 mm) even greater than the activity of the gentamicin positive control (21.5 mm). E. coli and P. aeruginosa bacteria were resistant when exposed to the concentration of 100 mg/ml of these extracts. P. aeruginosa bacteria were identified to be sensitive to the aqueous and ethanolic extract of the miracle fruit berry at a concentration of 100 mg/ml.

The antimicrobial effect against Vibrio parahaemolyticus isolated from shrimp farms in the province of Guayas was tested in commonly used plants. This bacterium causes mild gastroenteritis in humans due to the consumption of infected shellfish, it generally lives in tropical and temperate coastal areas [10]. The results showed that a higher percentage of extraction when using distilled water followed by ethanol and methanol. Aqueous extracts yields were 38.28% for basil leaf, 26.85% for Cananga odorata flowers, 22.53% for lemon verbena leaf, and 21.53 % for Baccharis latifolia leaves.

The test of plant extracts that showed antibacterial activity are eucalyptus leaf, guava leaf, basil leaf, chilca leaf. The eucalyptus leaf methanolic extract had a 2.29 mm higher zone of inhibition compared to the 2.03 mm tetracycline antibiotic control. V. parahaemolyticus was susceptible with diameters of the zone of inhibition for the aqueous eucalyptus leaf extract (1.80 mm), guava leaf (1.12 mm), and chilca leaves (1.15 mm). The bacterium was resistant when exposed to a concentration of 200 mg/ml of the aqueous, ethanol and methanol extracts of the lemon verbena leaf and Cananga odorata flowers. The minimum inhibitory concentrations will be analyzed in all the samples using dilutions from 200 mg/ml to 70 mg/mL.

In this study, potentially effective plant extracts are suggested to replace conventional antibiotics that, due to their indiscriminate use, have caused the appearance of resistant bacteria. The extracts can be applied within medicine as an alternative for the generation of new natural medicines that are effective, healthy, and safe. Other uses of plant extracts include environmental applications for pathogenic microorganisms control that are environmental contaminants.

Concluding, the project seeks to develop extraction techniques of bioactive compounds from common plants and agro-industrial residues, to improve the yields by applying solvents without a high impact on the environment. The antibacterial activity of plant species was determined in vitro on selected microorganisms, but in vivo tests are necessary to assess whether these characteristics are maintained. This research contribute to learning about the use of extracts from common plants and agro-industrial residues. Antimicrobials from agro industrial residues are a viable option for applied circular bioeconomy generating new value-added commercial products. Food, Non-alcoholic beverages, packing, packaging, and environmental remediation can reuse/recycle/recovery their residues and therefore develop new production chains to improve their profitability, pursuing a sustainable use of Ecuadorian biodiversity.

References

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