Fermentation Microbiology (FM) | Applied Microbiology
Microbiol. Biotechnol. Lett. 2021; 49(2): 201-209
https://doi.org/10.48022/mbl.2101.01003
Lieu My Dong1*, Doan Trung Nam1, Tran Thi Phuong1, and Dang Kim Thuy2
1Faculty of Food Science and Technology, Ho Chi Minh City University of Food Industry, 140 Le Trong Tan, Tay Thanh Ward, Tan Phu District, Ho Chi Minh City 70000, Vietnam 2Department of Plant Cell Technology, Institute of Tropical Biology, 9/621 Ha Noi highway, Ho Chi Minh City 70000, Vietnam
Correspondence to :
Dong Lieu, lieudong289@gmail.com
Agarwood (Aquilaria spp) has high economic value. However, essential oil production from agarwood is a time-consuming process. Additionally, agarwood leaves have not been utilized even though they contain various bioactive ingredients. In this study, agarwood leaves were fermented using Lactobacillus plantarum ATCC 8014 with or without Stevia (4, 8, and 12%; v/v). The fermented fluid was mixed with maltodextrin (15%; w/v) and subjected to spray drying (inlet temperature, 120℃; outlet temperature, 65–70℃). The contents of polyphenols, polysaccharides, saponins, and flavonoids and the viability of L. plantarum were determined. Fermentation enhanced the levels of bioactive compounds. The contents of polyphenol (69.19 ± 4.05 mg GAE/g of sample), polysaccharide (20.75 ± 0.98 mg GE/g of sample), saponin (305.23 ± 4.21 mg OAE/g of sample), and flavonoid (7.86 ± 0.72 mg QE/g of sample), and the viability of L. plantarum (8.72 ± 0.17 log CFU/ml) were markedly upregulated in the samples containing Stevia (12%; v/v). This indicated that the supplementation of Stevia during fermentation decreases the fermentation time (9 h), upregulates bioactive compound production in agarwood leaves, enhances microencapsulation during spray drying, and increases the viability of L. plantarum under simulated gastric digestion conditions.
Keywords: Aquilaria spp, bioactive compounds, fermentation, spray drying, Stevia rebaudiana
Agarwood plant (
The extraction efficiency of bioactive compounds plays an important role to fully exploit these components from agarwood leaves. Various approaches are available such as microwave-assisted extraction, ultrasound-assisted extraction, and lactic fermentation, that improved the extraction efficiency of bioactive compounds from medicinal plants [5, 6]. Microwave-assisted extraction or ultrasonic- assisted extraction is the process of mechanically acting on the plant cell wall to disrupt and improve extraction efficiency [5]. However, this mechanical process often causes overheating during the treatment leading to the effect of bioactive compounds [7]. Unlike microwave or ultrasonic extraction, fermentation is conducted at a constant temperature and does not cause overheating during the fermentation process. Also, fermentation could promote the metabolism of biological substances that alter product properties for higher value [8]. Among other fermentation processes, lactic fermentation is being widely used in which
For extracting fluid from the herb, the preservation and maintenance of the bioactive compounds are very important. The making of powder products by spray drying method is commonly used because it offers many advantages such as; ease of use, prolonged storage time [14, 15]. Also, this method was proven effective in the packaging of food ingredients sensitive to heat as polyphenols, anthocyanins, β-carotene, and carotenoids, as well as protect microorganisms under the effect of hightemperature spray drying because the carrier acts as a coating material [16, 17]. Although many studies on the extraction of biological compounds from medicinal plants using fermentation processes, studies on agarwood leave supplemented with stevia and evaluated the ability to maintain these compounds as well as the viability of probiotic bacteria was poorly reported. Therefore, this study evaluated the effect of fermentation, rate supplement stevia, and spray drying process on the extraction efficiency of bioactive compounds from agarwood leaves. The evaluation criteria are the total polyphenols, total polysaccharides, total saponins, total flavonoid contents, and
Stevia (
The milled agarwood was fermented by
Agarwood extract mixture after fermentation was supplemented with maltodextrin (PCT0611, India) 15% (w/v) and spray-dried with parameters: 4.5 ml/min, injector diameter 0.5 mm, the pressure was 2 atm, the inlet temperature was 120℃, the outlet temperature was 65–70℃. The bioactive compounds content and the
Determination of total phenolic content. Total phenolic content was conducted as described by Vuong
Determination of total polysaccharide content. Total polysaccharide content was conducted according to the description of Ly
Determination of total flavonoid content. Total flavonoid content was described by Zhishen
Determination of total saponin content. Total saponin content was performed as described by Chen
Test for the viability of
The 4 g sample was incubated in 36 ml of SGF medium for 2 h at 37℃, the sample was then transferred to SIF medium and incubated for 4 h at 37℃. The viability of
Statistical analysis. All experiments were repeated three times, results presented as mean ± standard deviation. Results were calculated using Microsoft Office Excel 2019 software and SPSS 20.0 statistical software. ANOVA analysis results with 95% confidence, comparing the differences between the treatments through the Tukey and Duncan test.
The effect of the lactic fermentation process with or without stevia supplement on the ability to extract bioactive compounds was shown in Figs. 2, 3. In the sample without adding stevia, the content of polyphenol, saponin, and polysaccharide increased significantly (
The results show that
The study results also indicated that the
Improving the extraction efficiency of bioactive compounds as well as increase the probiotic viability after the fermentation process plays an important role. The results also showed that the density of
The effect of spray drying on bioactive compounds and the
The spray drying process creates a powder product, making it easy to use and prolonging product storage time. However, for bioactive substances and probiotics, high temperatures in the spray-drying process should concern. Tchabo
Maltodextrin is a commonly used carrier in spray drying because of its properties as a prebiotic that protects probiotic bacteria, improves the recovery efficiency of bioactive compounds, is cheap, and prevents adhesion to the wall of equipment when spray drying [15, 16]. However, to further improve the protective effect of the wall materials, adjuvant compounds are often used. Research by Çam
The viability of
The viability of probiotic bacteria in gastrointestinal conditions plays an important role, determining the health benefits that this strain brings. In the SGF condition, low pH inhibits microbial growth and reduces viable probiotic bacteria [35]. Depending on the strain, the ability to survive under these conditions varies. Previous studies indicated that free-form probiotic bacteria exhibited poor viability in gastrointestinal conditions. In the study of Ding
The results showed that
The authors have no financial conflicts of interest to declare.
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