Abstract
In this study, PLA composites were prepared by extracting the active substance from laurel leaves (Laurus nobilis L.) in order to give antibacterial property to polylactic acid (PLA) which is a biodegradable polymer.
S. Enteritidis 13076 isolates were used as bacteria under antibacterial analyzes. The antibacterial effect and percentage of laurel leaf extract was determined, and this ratio was applied to PLA composite films.
1. Introduction
Biodegradable polymers are of great importance in many areas of technological development. In order to meet the growing demand for sustainability and environmental cleanliness, efforts are being made to develop food packaging materials that can be completely degraded in the environment.
As biopolymers are biodegradable, they are transformed into environmentally friendly food packaging materials and are suitable for use. As biopolymers are biodegradable and renewable, they are seen as alternative substances of petroleum plastics.
Today, the development of technology has led to the formation of synthetic biopolymers, including polylactic acid (PLA), polycaprolactone (PCL), polyglycolic acid (PGA), polyvinyl alcohol (PVA), and polybutylene succinate PBS.
The advantages of synthetic biopolymers include the development of many properties such as strength, flexibility, high gloss, clarity and tensile strength as well as the potential to create a sustainable industry [1].
The use of polylactic acid (PLA), one of the biodegradable polymers, is quite effective nowadays. PLA is biodegradable, biocompatible and non-toxic polyester and it is transparent, high modulus and strength and is a good alternative for petroleum-derived polymers.
PLA has many characteristics such as good processing properties, adjustable degradation rates and pharmacokinetic and pharmacological efficacy [2]. In the field of plastic applications, packaging, textile applications, agricultural products, disposable products and medical field provides a wide range of use [3].
In recent years, due to the emergence of many negative effects of synthetic antibacterial agents on human health, there is an increasing interest and need for agents obtained from natural sources. Essential oils obtained from plants have been shown to have antimicrobial, antifungal and antioxidant properties [4].
Dried leaves and essential oil of laurel (Laurus Nobilis L.) are used as a flavor and food preservative in the food industry. In the studies, the main components were found to be 1,8-cineole, linalol, transsabinene hydrate, a-terpinyl-acetate, methyl eugenol, sabine and eugenol [5].
2. Materials and Methods
2.1. Material
The laurel leaves (Laurus nobilis L.) used in the study were collected from the Black Sea Region. Ingeo™ Biopolymer 2003D from PLA Natureworks is used in the experiment. PLA used in the experiments contained 96% poly (L-lactic acid) (PLLA) and 4% poly (D-lactic acid) (PDLA).
2.2. Method
In this study, the antibacterial effect of laurel leaf extract was made according to Wang and Rham (2015). Plate Count Agar (PCA) was used as medium. For the purpose of sowing, the drip plaque method was applied followed by decimal dilutions.
At the same time, in order to determine the qualitative antibacterial effect, the discs were sterilized by the laurel leaf extract and disc diffusion method was applied. After determining the antibacterial effect and percentage of laurel leaf extract, this ratio was applied to PLA composite films.
PLA composite films were prepared using solvent casting method. The PLA was mixed with chloroform and added to the resulting solution with a 33% bay extract and mixed for 1 day using a magnetic stirrer. The resulting solution was poured into the sterilized petri dish and dried under room conditions for 7 days.
3. Results and Discussion
In this section, the laurel leaf extract and the composite film prepared by PLA are given the results of antibacterial analysis. As a result of the droplet method applied in Figure 1, the antibacterial effect of laurel leaf extract on S. Enteritidis ATCC 13076 was given.
At the end of the incubation period, no significant growth was observed around the surface where the leaf extract was contacted.
Figure 1. Anti bacterial effect of laurel leaf extract on S. Enteritidis ATCC 13076
The results of microbiological planting for PLA composite film prepared with laurel leaf extract and laurel leaf extract for quantitative effect are shown in Table 1 and Table 2.
Table 1. Laurel leaf extract microbiological sowing results
Table 2. Results of microbiological analysis of PLA film prepared with laurel leaf extract
C.f.u.: Colony forming unit
4. Conclusion
As a result of the studies, laurel leaf extract had an antibacterial effect on S. Enteritidis 13076 strain. As a result of microbiological cultivation, as shown in Table 1, laurel leaf extract showed a significant antibacterial effect on S. Enteritidis ATCC 13076 strain.
As a result of the sowing of PLA film prepared with the same amount of laurel leaf extract, no antibacterial effect on said microorganism was found (Table 2).
This is due to the fact that volatile oils having an antibacterial effect such as 1,8 cineole, which is one of the main components of Laurus nobilis L. may be flushed with chloroform while PLA films are dried.
Feza Geyikçi
Ondokuz Mayıs University
Faculty of Engineering
Department of Chemical Engineering
Ayça Aydın
Ondokuz Mayıs University
Faculty of Engineering
Department of Chemical Engineering
Belgin Sırıken
Ondokuz Mayıs University
Faculty of Veterinary Medicine
References
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[4] Chen C., Xu Z., Ma Y., Liu J., Zhang Q., Tang Z., Fu K., Yang F., Xie J.(2018). Properties, vapour-phase antimicrobial and antioxidant activities of active poly(vinyl alcohol) packaging films incorporated with clove oil. Food Control 88, 105-112.
[5] Vilela J., Martins D., Monteiro-Silva F., González-Aguilar G., Almeida J., Saraiva C. (2016). Antimicrobial effect of essential oils of Laurus nobilis L. and Rosmarinus officinallis L. on shelf-life of minced “Maronesa” beef stored under different packaging conditions. Food Packaging and Shelf Life, 8, 71-80.
