Strategic ultrasound-induced stress response of lactic acid bacteria on enhancement of β-glucosidase activity for bioconversion of isoflavones in soymilk

Comparative physiological and transcriptomic analysis of sono-biochemical control over post-acidification of Lactobacillus delbrueckii subsp. bulgaricus

Thermosonication (UT) prestress treatments combining with varied fermentation patterns has been revealed as an effective method to regulate post-acidification as exerted by Lactobacillus delbrueckii subsp. bulgaricus (L. delbrueckii), but sono-biochemical controlling mechanisms remain elusive. This study employed physiological and transcriptomic analysis to explore the response mechanism of L. delbrueckii to UT-induced microstress (600 W, 33 kHz, 10 min). UT stress-induced inhibition of acidification of L. delbrueckii during (post)-fermentation was first confirmed, relying on the UT process parameters such as stress exposure duration and UT power. The significantly enhanced membrane permeability in cells treated by 600 W for 10 min than the microbes stressed by 420 W for 20 min suggested the higher dependence of UT-derived stresses on the treatment durations, relative to the ultrasonic powers. In addition, ultrasonication treatment-induced changes in cell membrane integrity enhanced and/or disrupted permeability of L. delbrueckii, resulting in an imbalance in intracellular conditions associated with corresponding alterations in metabolic behaviors and fermentation efficiencies. UT-prestressed inoculum exhibited a 21.46% decrease in the membrane potential during the lag phase compared to untreated samples, with an intracellular pH of 5.68 ± 0.12, attributed to the lower activities of H+-ATPase and lactate dehydrogenase due to UT stress pretreatments. Comparative transcriptomic analysis revealed that UT prestress influenced the genes related to glycolysis, pyruvate metabolism, fatty acid synthesis, and ABC transport. The genes encoding 3-oxoacyl-[acyl-carrier-protein] reductases I, II, and III, CoA carboxylase, lactate dehydrogenase, pyruvate oxidase, glucose-6-phosphate isomerase, and glycerol-3-phosphate dehydrogenase were downregulated, thus identifying the relevance of the UT microstresses-downregulated absorption and utilization of carbohydrates with the attenuated fatty acid production and energy metabolisms. These findings could contribute to provide a better understanding of the inactivated effects on the post-acidification of L. delbrueckii by ultrasonic pretreatments, thus providing theoretical basis for the targeted optimization of acidification inhibition efficiencies for yogurt products during chilled preservation processes.

Effect of ultrasonic pretreatment on fermentation performance and quality of fermented hawthorn pulp by lactic acid bacteria

In order to explore the effects of ultrasonic pretreatment on the fermentation performance and quality characteristics of fermented hawthorn pulp. Five types of fermented hawthorn pulp were obtained using 0 W for 5 min, 300 W for 5 min, 360 W for 5 min, 420 W for 5 min, 540 W for 5 min. The fermentation performance and quality of fermented hawthorn pulp were characterized. The results indicated Low power ultrasound (360 W) could improve the fermentation performance and quality of FHP, and high power ultrasound (540 W) could reduce the fermentation performance and quality. Under the ultrasonic condition of 360 W for 5 min; the cell membrane of lactic acid bacteria produced repairable damage and the morphology did not change significantly, the consumption of reducing sugar, total acid, soluble solids, amino nitrogen, conductivity, and sensory quality of the fermented hawthorn pulp reached the highest. The fermentation performance and quality of fermented hawthorn pulp were improved by the optimum ultrasonic treatment, which could be used as an effective and alternative method for producing FHP with good flavor, high bioactivity and good quality.

Fermented Vegetables: Health Benefits, Defects, and Current Technological Solutions

This review summarizes current studies on fermented vegetables, analyzing the changes in nutritional components during pickling, the health benefits of fermented vegetables, and their safety concerns. Additionally, the review provides an overview of the applications of emergent non-thermal technologies for addressing these safety concerns during the production and processing of fermented vegetables. It was found that vitamin C would commonly be lost, the soluble protein would degrade into free amino acids, new nutrient compositions would be produced, and the flavor correlated with the chemical changes. These changes would be influenced by the variety/location of raw materials, the original bacterial population, starter cultures, fermentation conditions, seasoning additions, and post-fermentation processing. Consuming fermented vegetables benefits human health, including antibacterial effects, regulating intestinal bacterial populations, and promoting health (anti-cancer effects, anti-diabetes effects, and immune regulation). However, fermented vegetables have chemical and biological safety concerns, such as biogenic amines and the formation of nitrites, as well as the existence of pathogenic microorganisms. To reduce hazardous components and control the quality of fermented vegetables, unique starter cultures, high pressure, ultrasound, cold plasma, photodynamic, and other technologies can be used to solve these problems.

The effects of ultrasound on probiotic functionality: an updated review

The effects of ultrasound (US) on probiotics, as health-promoting microbes, have attracted the attention of researchers in fermentation and healthy food production. This paper aims to review recent advances in the application of the US for enhancing probiotic cells' activity, elaborate on the mechanisms involved, explain how probiotic-related industries can benefit from this emerging food processing technology, and discuss the perspective of this innovative approach. Data showed that US could enhance fermentation, which is increasingly used to enrich agri-food products with probiotics. Among the probiotics, recent studies focused on Lactiplantibacillus plantarum, Lactobacillus brevis, Lactococcus lactis, Lactobacillus casei, Leuconostoc mesenteroides, Bifidobacteria. These bacteria proliferated in the log phase when treated with US at relatively low-intensities. Also, this non-thermal technology increased extracellular enzymes, mainly β-galactosidase, and effectively extracted antioxidants and bioactive compounds such as phenolics, flavonoids, and anthocyanins. Accordingly, better functional and physicochemical properties of prebiotic-based foods (e.g., fermented dairy products) can be expected after ultrasonication at appropriate conditions. Besides, the US improved fermentation efficiency by reducing the production time, making probiotics more viable with lower lactose content, more oligosaccharide, and reduced unpleasant taste. Also, US can enhance the rheological characteristics of probiotic-based food by altering the acidity. Optimizing US settings is suggested to preserve probiotics viability to achieve high-quality food production and contribute to food nutrition improvement and sustainable food manufacturing.

Sono-activation of food enzymes: From principles to practice

Over the last decade, sono-activation of enzymes as an emerging research area has received considerable attention from food researchers. This kind of relatively new application of ultrasound has demonstrated promising potential in facilitating the modern food industry by broadening the application of various food enzymes, improving relevant industrial unit operation and productivity, as well as increasing the yield of target products. This review aims to provide insight into the fundamental principles and possible industrialization strategies of the sono-activation of food enzymes to facilitate its commercialization. This review first provides an overview of ultrasound application in the activation of food protease, carbohydrase, and lipase. Then, the recent development on ultrasound activation of food enzymes is discussed on aspects including mechanisms, influencing factors, modification effects, and its applications in real food systems for free and immobilized enzymes. Despite the far fewer studies on sono-activation of immobilized enzymes compared with those on free enzymes, we endeavored to summarize the relevant aspects in three stages: ultrasound pretreatment of free enzyme/carrier, assistance in immobilization process, and modification of the already immobilized enzyme. Lastly, challenges for the scalability of ultrasound in these target areas are discussed and future research prospects are proposed.

Bioactivity of Organic Fermented Soymilk as Next-Generation Prebiotic/Probiotics Mixture

Fermented soymilk (soymilk yogurt) was made by fermenting soymilk with five probiotic bacterial strains (Lactobacillus plantarum ATCC 14917, Lactobacillus casei DSM 20011, Lactobacillus acidophilus ATCC 20552, Lactococcus thermophilus DSM 20259, and Bifidobacterium longum B41409) that were used as monocultures and combined with them as consortia cultures. Seven pathogenic strains, E. coli O157H7, S. aureus As4, S. typhimurium As3, S. shigae As2, L. monocytogenes As1, P. aeruginosa ATCC 27853, and B. cereus Dsmz 345, were used to study the antibacterial activity of fermented soymilk by agar well diffusion assay. Results indicated that Gram-negative pathogenesis was more sensitive to probiotic cultures than Gram-positive pathogenesis. E. coli O15H7, S. typhimirium As3, and Shigella shigae As2 were more sensitive to probiotic cultures, presenting inhibition zone diameters (IZA) ranging from 10 to 20 mm, 12 to 16 mm, and 10 to 16 mm, respectively. At the same time, P. aeruginosa Atcc 27853 showed the lowest (IZA), ranging from 3 mm to 8 mm. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined at various concentrations of soymilk fermented by T1, T4, and T5, ranging from 0.031 mg/mL to 1 mg/mL against pathogenic bacterial strains. The sensory properties of FSM were evaluated, and sensory analysis during soymilk fermentation showed significant improvement. The effect of shelf life (storage period) on FSM quality and properties was evaluated; during shelf life (storage period), FSM saved its properties and quality after 28 days of cold storage. Finally, it was stated that the soymilk yogurt can be used as a substitute for buffalo and cow milk for therapeutic feeding in the future.

Enhancement of Antioxidant Activities in Black Soy Milk through Isoflavone Aglycone Production during Indigenous Lactic Acid Bacteria Fermentation

Black soybeans contain high antioxidant compounds such as isoflavone but mainly in glucoside form, with low antioxidant activities. Fermentation by lactic acid bacteria (LAB) can enhance the antioxidant properties, but its ability is strain-dependent. This study aims to study the ability of Indonesian indigenous LAB, Lactiplantibacillus plantarum WGK 4, Streptococcus thermophilus Dad 11, and Lactiplantibacillus plantarum Dad 13, to enhance the antioxidant properties during black soy milk fermentation. Fermentation was carried out at 37 °C for 24 h. Viable cell, acid production, Folin–Ciocalteu assay, antioxidant activity (DPPH), isoflavone aglycone daidzein and genistein, and β-glucosidase activity were measured every six hours. All LAB strains could grow well during the fermentation of black soy milk. Lactiplantibacillus plantarum WGK 4 produced the highest acid (1.50%). All three LAB strains could enhance antioxidant activity (DPPH) from 24.90% to 31.22–38.20%, followed by increased isoflavone aglycone. All strains could increase daidzein and genistein content, ranging from 61% to 107% and 81% to 132%, respectively. All three Indonesian indigenous LAB enhanced antioxidant properties of black soy milk relatively at the same level and potentially could be used as a starter culture of black soy milk fermentation.

Assessment of Ultrasonic Stress on Survival and β-Glucosidase Activity of Encapsulated Lactiplantibacillus plantarum BCRC 10357 in Fermentation of Black Soymilk

The enhanced β-glucosidase activity of encapsulated Lactiplantibacillus plantarum BCRC 10357 within calcium alginate capsules was investigated by ultrasonic stimulation to induce the stress response of the bacteria for the biotransformation of isoflavones in black soymilk. The effects of various ultrasound durations, sodium alginate concentrations (% ALG), and cell suspensions on the β-glucosidase activity of encapsulated bacteria were explored. The β-glucosidase activity of encapsulated L. plantarum BCRC 10357 with ultrasonic stimulation (40 kHz/300 W) was greater than that without ultrasound. With 20 min of ultrasonic treatment, the β-glucosidase activity of encapsulated L. plantarum BCRC 10357 from 2% ALG/0.85% NaCl cell suspension was 11.47 U/mL at 12 h, then increased to 27.43 U/mL at 36 h and to 26.25 U/mL at 48 h in black soymilk at 37 °C, showing the high adaptation of encapsulated L. plantarum BCRC 10357 encountering ultrasonic stress to release high β-glucosidase until 48 h, at which point the ratio of isoflavone aglycones (daidzein and genistein) in total isoflavones (daidzin, genistin, daidzein, and genistein) was 98.65%, reflecting the effective biotransformation of isoflavone glycosides into aglycones by β-glucosidase. In this study, the survivability and β-glucosidase activity of encapsulated L. plantarum BCRC 10357 were enhanced under ultrasonic stimulation, and were favorably used in the fermentation of black soymilk.

Effect of low-level ultrasound treatment on the production of L-leucine by Corynebacterium glutamicum in fed-batch culture

Various process intensification methods were proposed to improve the yield, quality, and safety of fermented products. Here, we report the enhancement of L-leucine production by Corynebacterium glutamicum CP using ultrasound-assisted fed-batch fermentation. Response surface methodology was employed to optimize the sonication conditions. At an ultrasonic power density of 94 W/L, frequency of 25 kHz, interval of 31 min, and duration of 37 s, C. glutamicum CP produced 52.89 g/L of L-leucine in 44 h, representing a 21.6% increase compared with the control. The production performance of L-leucine was also improved under ultrasonic treatment. Moreover, the effects of ultrasound treatment on the fermentation performance of L-leucine were studied in terms of cell morphology, cell membrane permeability, and enzyme activity. The results indicate that ultrasonication is an efficient method for the intensification of L-leucine production by C. glutamicum CP.

Impact of processing technologies on isoflavones, phenolic acids, and antioxidant capacities of soymilk prepared from 15 soybean varieties

In the present study, soymilk samples were prepared from 15 soybean varieties by employing dry method-raw slurry filtration (D-BAF), dry method-cooked slurry filtration (D-BBF), wet method-raw slurry filtration (W-BAF), and wet method-cooked slurry filtration (W-BBF). Different varieties of soybean and processing techniques were found to impose a significant impact on total phenolics, total flavonoids, phenolic acids, isoflavones and antioxidant capacity of soymilk samples. Overall, the soymilk prepared by W-BAF exhibited a higher level of total phenolic content and antioxidant activity. The soymilk samples prepared by W-BBF presented higher values for total flavonoid content and ferric-reducing antioxidant power assay. The soymilk prepared by W-BBF presented higher subtotal values of phenolic acids. In comparison, the soymilk prepared by D-BAF exhibited high amount of total isoflavones followed by the soymilk processed by W-BAF. Overall, the wet method was found to be responsible for improved phenolic contents and antioxidant activity of soymilk sample.

Evaluation of Semi-Solid-State Fermentation of Elaeocarpus serratus L. Leaves and Black Soymilk by Lactobacillus plantarum on Bioactive Compounds and Antioxidant Capacity

Elaeocarpus serratus L. leaves (EL) containing phenolic compounds and flavonoids, including myricitrin with pharmacological properties, could be valorized as nutritional additive in foods. In this study, the semi-solid-state fermentation of EL and black soymilk (BS) by Lactobacillus plantarum BCRC 10357 was investigated. Without adding EL in MRS medium, the β-glucosidase activity of L. plantarum quickly reduced to 2.33 ± 0.15 U/mL in 36 h of fermentation; by using 3% EL, the stability period of β-glucosidase activity was prolonged as 12.94 ± 0.69 U/mL in 12 h to 13.71 ± 0.94 in 36 h, showing positive response of the bacteria encountering EL. Using L. plantarum to ferment BS with 3% EL, the β-glucosidase activity increased to 23.78 ± 1.34 U/mL in 24 h, and in the fermented product extract (FPE), the content of myricitrin (2297.06 μg/g-FPE) and isoflavone aglycones (daidzein and genistein, 474.47 μg/g-FPE) at 48 h of fermentation were 1.61-fold and 1.95-fold of that before fermentation (at 0 h), respectively. Total flavonoid content, myricitrin, and ferric reducing antioxidant power in FPE using BS and EL were higher than that using EL alone. This study developed the potential fermented product of black soymilk using EL as a nutritional supplement with probiotics.

Biotransformation of two citrus flavanones by lactic acid bacteria in chemical defined medium

Microbial processes are being developed to transform flavonoid glycosides to varieties of metabolites with higher bioavailability. The aim of this study was to determine the metabolic activity and survival of five lactic acid bacteria (LAB) stains (L. rhamnosus LRa05, L. casei LC89, L. plantarum N13, L. acidophilus LA85, and L. brevis LB01) in two different citrus flavanone standards (hesperetin-7-O-rutinoside and naringenin-7-O-rutinoside). The enzymatic activity, metabolites, antioxidant activities, and α-glucosidase inhibition property in the two standards were also investigated before and after incubated with LAB. The medium contained standards permitted survival of the five LAB stains. All strains exhibited β-glucosidase activity. Of the five LAB strains tested, just L. plantarum N13 and L. brevis LB01 have the ability to metabolize hesperetin-7-O-rutinoside, only L. plantarum N13, L. acidophilus LA85, and L. brevis LB01 could metabolize naringenin-7-O-rutinoside, moreover, L. acidophilus LA85l was the strain with the highest biotransformation ratio of naringenin-7-O-rutinoside. L. acidophilus LA85 and L. plantarum N13 can degrade naringenin-7-O-rutinoside into naringenin. L. brevis LB01 can degrade hesperetin-7-O-rutinoside into hesperetin, 3-(4'-hydroxyphenyl)-2-propenoic acid, 3-(3'-hydroxy-4'-methoxyphenyl)hydracrylic acid, and 3-(4'-hydroxyphenyl)propionic acid. Incubation of L. acidophilus LA85 in naringenin-7-O-rutinoside solution supposed no apparent influence in the biological activities that tested. L. acidophilus LA85 may potentially contribute to the bioavailability of citrus flavanones, and to be applied as functional cultures to obtain more bioavailable and bioactive metabolites in food products or in the human gastrointestinal tract.

Recent nano-, micro- and macrotechnological applications of ultrasonication in food-based systems

There is a neoteric and rising demand for nutritional and functional foods which behooves food processors to adopt processing techniques with optimal conservation of bioactive components in foods and with minimal pernicious impacts on the environment. Ultrasonication, a mechanochemical technique has proven to be an efficacious panacea to these concerns. In this review, an analytic exploration of recent researches and designs regarding ultrasound methodology and equipment on diverse food systems, technological scales, procedural parameters and outcomes of such experimentations optimally scrutinized. The relative effects of ultrasonication on food formulations, components and attributes such as nanoemulsions, nanocapsules, proteins, micronutrients, sensory and mechanical characteristics are evaluatively delineated. In food systems where ultrasonication was employed, it was found to have a remarkable effect on one or more quality parameters. This review is a supplementation to the pedagogical awareness to scholars on the suitability of ultrasonication for research procedures, and a call to industrial food brands on the adoption of this technique for the development of foods with optimally sustained nutrient profiles.