Fermentation Microbiology (FM) | Applied Microbiology
Microbiol. Biotechnol. Lett. 2021; 49(3): 346-355
https://doi.org/10.48022/mbl.2106.06011
Lieu My Dong1*, Nguyen Thi Thuy Linh1, Nguyen Thi Hoa1, Dang Thi Kim Thuy2, and Do Dang Giap2
1Faculty of Food Science and Technology, Ho Chi Minh City University of Food Industry, Ho Chi Minh City 72009, Vietnam 2Department of Plant Cell Technology, Institute of Tropical Biology, Ho Chi Minh City 71308, Vietnam
Correspondence to :
My Dong Lieu, lieudong289@gmail.com
Ngoc Linh ginseng is one of the most valuable endemic medicinal herbs in Vietnam. In this study, Ngoc Linh ginseng callus was fermented by Lactobacillus plantarum ATCC 8014 (at 6, 7, and 8 log CFU/ml) to evaluate the extraction efficiency of bioactive compounds. The post-fermentation solution was spray-dried using maltodextrin with or without Stevia rebaudiana (3% and 6% v/v) as the wall material. Bioactive compounds such as polyphenols, polysaccharides, and total saponins, and L. plantarum viability during fermentation and after spray-drying, as well as under simulated gastric digestion, were evaluated in this study. The results showed that probiotic density had a significant effect on bioactive compounds, and L. plantarum at 8 log CFU/ml showed the best results with a short fermentation time compared to other tests. The total content of polyphenols, polysaccharides, and saponins reached 5.16 ± 0.18 mg GAE/g sample, 277.2 ± 6.12 mg Glu/g sample, and 4.17 ± 0.15 mg/g sample, respectively after 20 h of fermentation at the initial density of L. plantarum (8 log CFU/ml). Although there was no difference in the particle structure of the preparation, the microencapsulation efficiency of the bioactive compound in the samples containing S. rebaudiana was higher than that with only maltodextrin. The study also indicated that adding S. rebaudiana improved the viability of L. plantarum in gastric digestion. These results showed that S. rebaudiana, a component stimulating probiotic growth, combined with maltodextrin as a co-prebiotic, improved the survival rate of L. plantarum in simulated gastric digestion.
Keywords: Bioactive compounds, Ngoc Linh ginseng, Stevia rebaudiana, probiotic, spray drying
Ngoc Linh ginseng has the scientific name of
The methods extraction of bioactive compounds is used commonly in previous studies such as the effect of microwaves [7], assisted by ultrasound [8], heat reflux systems (Soxhlet) [9], etc. In addition to these mechanical agents, the use of microorganisms in the extraction of bioactive compounds from medicinal plants has also received much attention [10] due to the absence of thermal effects in the culture process or the use of toxic solvents. In previous studies have shown the potential of lactic acid bacteria in the extraction and metabolism of bioactive substances from plants [11]. The fermentation process disrupts the structure of the cell wall to release bioactive compounds and antioxidants [12]. Besides, the lactic fermentation process might improve the sensory properties and nutritional value, inhibit harmful microorganisms, and increase the storage time of products [13]. Additionally, lactic acid bacteria sources after the fermentation process play a role as probiotics, providing health benefits. Thus, fermented Ngoc Linh ginseng callus by lactic bacteria could not only improve the bioactive compounds but also provide a probiotic source. However, after the fermentation process, the bioactive compounds and probiotic source should be ensured and maintained during storage time, which the spray-drying technique could provide this value.
The spray-drying method transforms the liquid from the liquid to a fine-dried form by transferring the liquid to a hot drying medium [14]. This method can produce the purest and best-sized powder products under high aseptic conditions that can easily transport and increased storage time [15]. Besides, the spray-drying technique acts as a microencapsulation process that protects probiotic bacteria from adverse conditions such as preservation and simulated gastric digestion [16]. In the spray drying technique, the product could be in powder or flocculant form that depends on the properties of the wall materials and the spray dryer [14]. There are many wall materials, using for the spray drying process, of which maltodextrin is commonly used due to reducing cling, sticky, and increasing the free-flowing properties of the spray-drying powder [17]. To increase the protective efficiency during the spray drying process, the combination of wall materials was often used. Besides, the sensory property plays an important role in deciding the product choice of consumers in which the sweetness of the product is often concerned. Therefore, the supplement wall material for the spray drying process should ensure the protective efficiency of bioactive compounds and probiotic bacteria, as well as have a good taste. Previous studies showed that
Microbiological strain:
Stevia (
Biomass of Ngoc Linh ginseng callus (Fig. 1) weighed accurately (2 g ± 0.01) crushed, extracted with distilled water twice at the rate of 1:35 (w/v). The callus biomass extract was then supplemented with strains of bacteria
Ngoc Linh ginseng extract afterfermentation was supplemented with 15% maltodextrin (Himedia, India) with or without stevia leaves extract (3% and 6% v/v). The mixture was then spray-dried (SD-1000, Eyela, Japan) according to the spray structure with the following parameters: input flow 30 m3/h, nozzle diameter 0.71 mm, the pressure was 2 atm, the inlet temperature was 120°C, outlet temperature was 65−75°C. Sample spray drying without Stevia leaves extract was considered as the control samples. The preparations after spray-drying were evaluated the particle shape by a scanning electron microscope (SEM). The content of bioactive compounds and
Determination of total polyphenol content. The total phenolic content was performed as described by Leamsomrong
Total polysaccharide content determination. The total polysaccharide content was conducted as described by Lieu
Total saponin content determination. The total saponin content was carried out as described by Yang
Determination of the density of probiotic bacteria. One milliliter of fermentation solution or 1 gram of sample diluted to different concentrations was carried out on MRS agar. Samples were then density determined after 48 h of incubation at 37°C.
Determination of
The 4-gram sample was incubated in 36 ml of SGF medium for 2 h at 37°C, the sample was then transferred to SIF medium and incubated for 4 h at 37°C. The viability of
All experiments were repeated three times, results presented as mean ± standard deviation. Results are calculated and shown graph graphically by Sigma plot software. ANOVA analysis results with 95% confidence, compare the differences between the treatments through the LSD and Tukey tests by Sigma plot software.
The effect of lactic fermentation on the content of bioactive compounds in Ngoc Linh ginseng callus and
The
In previous studies showed that lactic acid bacteria could inhibit pathogenic bacteria and reduce food spoilage [11]. Besides, lactic fermentation significant impact on the bioactive compounds from plants [12, 23]. Hou
Besides, the prolonged fermentation time showed to affect the content of bioactive compounds as well as the viability of lactic bacteria (Figs. 2 and 3). The low pH environment containing acetic and lactic acids at a high concentration affected lactic bacteria [27]. This causes the viability of
The effect of maltodextrin with or without stevia supplement on encapsulation efficiency of bioactive compounds and
Ensuring the bioactive compounds and probiotic source during storage time after fermentation is necessary, and the spray-drying technique could provide this value. This method’s produce can easily transport, increased storage time [15]. The product capsule size from spray drying was significantly smaller than other prevalent techniques [27]. This helps to minimize its influence on the sensory properties of foods. However, this method also impacts the components using for spray drying. The effect of the spray drying process on the surface structure of microencapsulation particles has been reported in previous studies. A previous study using wall materials including maltodextrin, whey protein, and galacto-oligosaccharides in combination or individual indicated that there was no difference in the surface structure of particles among these preparations [16]. Similarly, Fritzen-Freire
The wall material components have been proven to affect the microencapsulation efficiency [14]. The combination of maltodextrin with other wall materials showed to improve the microencapsulation efficiency [16, 33]. Maltodextrin combined with whey protein significantly enhanced
The effect of SGF and SIF on
The probiotic viability under gastrointestinal conditions is necessary to ensure the benefits this microorganism brings. The low pH and digestion enzymes of the SGF condition were significantly lethal to probiotics compared to the SIF condition [16]. The previous evaluations have shown that free probiotic cells could not overcome the SGF condition [27]. Therefore, the microencapsulating probiotic is essential to help these strains overcome this adverse medium and provide health value. A previous study showed that microencapsulation by spray drying with maltodextrin as wall material improved
In summary, the fermentation time, and the
The authors express their deepest gratitude to the Faculty of Food Science and Technology, Ho Chi Minh City University of Food Industry, and Department of Plant Cell Technology, Institute of Tropical Biology, Ho Chi Minh City, Vietnam for providing research facilities.
The authors have no financial conflicts of interest to declare.
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