Controlled Fermentation Process Research Articles

Fast and Non-Invasive Evaluation of Yeast Viability in Fermentation Processes Using Raman Spectroscopy and Machine Learning

Fermentation processes used for producing alcoholic beverages such as beer, wine, and cider have a long history, having been developed early on across different civilizations. In most instances, yeast strains are used for fermentation processes, e.g., at breweries and wineries. Monitoring of yeast viability, cell count, and growth behavior is essential to ensure a controlled fermentation process. However, classical microbiological techniques to monitor fermentation process parameters are time-consuming and require sampling, along with the risk of contamination. Nowadays, industries are moving toward automation and digitalization. This necessitates state-of-the-art process analytical technologies to ensure an efficient and controlled process to obtain high-quality product outputs. Hence, there is a strong need for a fast, non-invasive, and generally applicable method to evaluate the viability of yeast cells during fermentation to warrant the standardization and purity of produced products in industrial applications. The aim of our study is to discriminate between viable and non-viable yeast in various culture media using Raman spectroscopy (RS) followed by data analysis with machine learning (ML) tools. These techniques allow for rapid, non-invasive analysis addressing the limitations of traditional methods. The present work primarily focuses on the evaluation of RS combined with predictive ML models in a non-real-time setting. Our goal is to adapt these techniques for future application in real-time monitoring and determination of yeast viability in biotechnological processes. We demonstrate that RS, in combination with ML, is a promising tool for non-invasive inline monitoring of fermentation processes.

Fermentative capabilities of Saccharomyces yeast and lactic acid bacteria strains in pure and mixed cultures during Borassus akeassii sap fermentation

Palm wine produced by natural fermentation of Borassus akeassi raw sap exhibits great variability in physicochemical, sensory, and microbiological quality. This study aimed to improve the production process, safety and sensory quality of Borassus akeassii wine. Eight types of wine were produced, seven of which were obtained from a controlled fermentation process for 72 h using Saccharomyces cerevisiae and/or lactic acid bacteria strains previously isolated from palm wine in Burkina Faso. Physicochemical and microbiological characteristics of the wines were determined using standard methods while their sensory analysis was carried out on a panel of 24 tasters, including 15 regular consumers from Banfora and 9 naive consumers from Ouagadougou.The pH ranged from 5.30±0.14 to 5.99±0.00, acidity from 0.39±0.06 to 1.66±0.12 (%), the brix degree from 2.95±0.07 to 5.2±0.00 and alcohol content from 1.92±0.00 to 5.87±0.00 (%). From the microbiological analyses, we obtained a total count of aerobic flora and coliforms below 1 CFU/mL in the conditioned wine. The sensory characteristics of the wines differed significantly as the panelist preferred the wines fermented with Saccharomyces cerevisiae PW3 and PW16 strains, respectively. The study revealed that the presence of Saccharomyces cerevisiae PW3 and PW16 strains and lactic acid bacteria promoted the production of higher quality wines with improved microbiological and sensory properties. They therefore stand as suitable starter culture candidates for the production of quality wines from Borassus akeassii sap.

Influence of Temperature-Controlled Fermentation on the Quality of Mild Coffee (Coffea arabica L.) Cultivated at Different Elevations

Controlled fermentation processes have high potential for improving coffee quality. The effect of fermentation temperature on beverage quality was investigated with coffee cultivated at elevations between 1166 and 1928 m. A completely randomized design was carried out at five elevation ranges at 200 m intervals in five farms per elevation range, and two temperatures (15 °C and 30 °C), which were maintained in a temperature-controlled bioreactor. Each temperature-controlled fermentation batch had a spontaneous fermentation batch (control treatment). Microbial identification of LAB and yeast was performed using a Biolog™ MicroStation™ ID System, and cup quality tests were performed following the SCA protocol. Tests conducted at 15 °C showed higher microbial community activity on the substrates used, indicating greater transformation potential than those conducted at 30 °C or those of spontaneous fermentation. According to Wilcoxon and Kruskal–Wallis tests, temperature-controlled fermentation resulted in high-quality coffee for all elevation ranges, with coffee from higher elevations and processed at controlled temperatures of 15 °C receiving the highest cup scores compared to coffee that was subjected to 30 °C. These results suggest that controlled temperature can be used to design standardized fermentation processes in order to enhance coffee quality through differentiated sensory profiles.

Recovery of Potential Starter Cultures and Probiotics from Fermented Sorghum (Ting) Slurries.

Fermented foods are thought to provide a source of probiotics that promote gut health. Consequently, isolation and characterization of fermented food strains and their applications in a controlled fermentation process or as probiotics present a new facet in this area of research. Therefore, the current study sought to identify dominant strains in sorghum-fermented foods (ting) and characterize their probiotic potential in vitro. Recovered isolates were identified as Lactobacillus helveticus, Lactobacillus amylolyticus, Lacticaseibacillus paracasei, Lacticaseibacillus paracasei subsp paracasei, Lactiplantibacillus plantarum, Levilactobacillus brevis, Loigolactobacillus coryniformis and Loigolactobacillus coryniformis subsp torquens based on the their 16S rRNA sequences. Increased biomass was noted in seven out of nine under a low pH of 3 and a high bile concentration of 2% in vitro. Bactericidal activities of isolated LABs presented varying degrees of resistance against selected pathogenic bacteria ranging between (1.57 to 41 mm), (10 to 41 mm), and (11.26 to 42 mm) for Salmonella typhimurium ATTC 14028, Staphylococcus aureus ATTC 6538 and Escherichia coli ATTC8739, respectively. Ampicillin, erythromycin, mupirocin, tetracycline and chloramphenicol were able to inhibit growth of all selected LABs. Thus, isolates recovered from ting partially satisfy the potential candidacy for probiotics by virtue of being more tolerant to acid and bile, antibacterial activity and antibiotic resistance.

Ultrasound-Assisted Lactic Acid Fermentation of Bakraei (Citrus reticulata cv. Bakraei) Juice: Physicochemical and Bioactive Properties

In this study, ultrasonication (US) (50 W, 30 kHz, 1–6 min) was used to increase the efficiency of Limosilactobacillus reuteri PTCC 1655 fermentation process (37 °C; 30 h) of Bakraei juice. Total sugars, pH, Brix, organic acids, vitamin C, polyphenols, antioxidant activity, α-amylase inhibition and anti-inflammatory properties were measured during the fermentation period. The results showed that by increasing the ultrasound time up to 5 min, pH, vitamin C, citric acid, and polyphenolic compounds decreased, while lactic acid, antioxidant capacity, α-amylase inhibition and anti-inflammatory properties were increased. When the ultrasound time was increased up to 6 min, compared to the non-ultrasound-treated sample, the efficiency of the fermentation process decreased and promoted a decrease in the microbial population, lactic acid levels, antioxidant activity, α-amylase inhibition, and anti-inflammatory properties of the juices. The initial anti-inflammatory activity (11.3%) of juice reached values of 33.4% and 19.5%, after US treatments of 5 and 6 min, respectively, compared to the non-sonicated juice (21.7%), after 30 h of fermentation. As a result, the use of ultrasound in the controlled fermentation process can increase the efficiency of fermentation process.

The characterization of the bioactive compounds in fermented papaya pulp and leaves: providing new insights on the anti-ageing potential

Nowadays, fermented food and beverages derived from plants have become popular choices for consuming functional foods as they provide enormous advantages to human health. Fermented food and beverage might offer more therapeutic benefits than natural nutrition. Papaya contains high antioxidant, antitumor, and immune regulatory effects due to its valuable phytochemical properties. Despite all the advantages, papaya leaves were underutilised as they have an astringent and bitter taste. During this study, papaya pulp and leaves underwent fermentation to enhance their functional properties and improve their taste and flavour. Both papaya pulp and leaves were fermented using mixed cultures of Komagataiebacter sp. bacteria and Dekkera sp. yeast and incubated under a controlled fermentation process. The supernatant extracted from both fermented papaya pulp and leaves was collected and its inhibitory effect towards the elastase, tyrosinase and acetylcholinesterase was analysed. Elastase and tyrosinase were employed for anti-ageing as increasing in dermal enzymatic activities will cause skin disorders. Meanwhile, acetylcholinesterase will affect the cholinergic crisis in the brain. Thus, inhibiting these enzymes is important for preventing hyperpigmentation, skin ageing and improving cognitive function. In comparison to non-fermented papaya pulp and leaves, the fermented papaya extracts demonstrated significant differences (P<0.05) in the inhibition effect against elastase, tyrosinase and acetylcholinesterase with an inhibitory value above 80%. Most of the flavonoids obtained in fermented papaya pulp and leaves were higher than non-fermented pulp and leaves. Protocatechuic acid was the highest compound in fermented papaya pulp (1.22±0.11 µg/mL), while vitexin (113.20±1.18 µg/mL), rutin (10.56±0.52 µg/mL), and ellagic acid (8.76±0.40 µg/mL) highly contained in fermented papaya leaves. The highest organic acids obtained from fermented papaya pulp and leaves acetic acid (13495.42±308.99 µg/mL and 18572.48±78.45 µg/mL), followed by quinic acid (2148.71±63.31 µg/mL and 984.40±2.29 µg/mL) and citric acid (802.57±17.68 µg/ mL and 151.83±6.50 µg/mL), respectively. The findings described the potential of fermented papaya pulp and leaves extracts as potential bio-ingredients to slow down ageing development

Investigation by High-Throughput Sequencing Methods of Microbiota Dynamics in Spontaneous Fermentation of Abruzzo (South Italy) Wines

Spontaneous wine fermentation is a meaningful topic that cannot be disregarded among winemakers and consumers due to the peculiarity of the organoleptic profile that it confers to the wine. Nevertheless, in this process the activity of indigenous microorganisms might be a threat. We studied the evolution of the spontaneous fermentation process in a traditional Italian winery in order to understand the origin of spoilage microorganisms, and to characterize the peculiarity of the microbiota associated with spontaneous fermentation. Six Trebbiano and Montepulciano wine production chains were monitored by plate counts made by OIV methods and by Illumina MiSeq technique. Despite some compositional deficiencies, all grape musts were characterized by a highly concentrated microbial population. Non-Saccharomyces yeasts revealed an unexpected tolerance to ethanol, which has contributed to the evolution of alcoholic fermentation. Lactic bacteria were detectable from the very first steps of the winemaking process, with a prevalence of Leuconostoc spp. which is nowadays, rarely isolated in wine. The combination between culture-dependent and high-throughput sequencing (HTS) approaches allowed to estimate microbial diversity and growth dynamics in wine fermentations of different grape varieties and under different treatments; these results could be used by winemakers as a starting point to drive a more mindful, accurate and, controlled fermentation process and to set up the most suitable environmental conditions to enhance wine singularities.

Production of dehairing protease by Bacillus cereus VITSN04: a model cradle-to-cradle approach for sustainable greener production of leathers

ABSTRACT Despite several attempts over decades, process scalability and sustainability remains a challenge to produce an environmental-friendly enzyme to gain industrial attention. In the present study, microbial degradation of chrome shavings (chromium-collagen leather waste) and the resulting collagen hydrolysate for producing the dehairing protease by Bacillus cereus VITSN04 were investigated in a lab-scale fermentor. Scale-up degradation of shavings resulted in higher recovery of collagen hydrolysate (76%) within 72 h compared to shake flasks (68% in 120 h). Earlier achieved medium composition of collagen hydrolysate (12 g L-1) and molasses (15 g L-1) appeared to induce amylase in high rate, despite maximal production of protease (203.8±0.18 U mL-1), which was analysed by ANS fluorescence spectroscopy. Optimization of the media containing collagen hydrolysate (12 g L-1) and molasses (5 g L-1) was effective in producing protease (170.6±0.1 U mL-1) and reduce the co-synthesis of amylase (48.2±0.09 U mL-1). The controlled fermentation process, by feeding molasses during exponential growth phase had enhanced dehairing protease production (∼2.96 fold). The produced protease then partitioned through biphasic system showed significant dehairing of goat skins in pilot scale. Thus, scalability of the process to produce dehairing enzymes using waste, generated at the site of its use offers hope for sustainable greener production of leathers.

Impact of Ferment Processing Parameters on the Quality of White Pan Bread

A controlled fermentation process using straight-grade wheat flour, commercially milled from a grist of Canada Western Red Spring (CWRS) wheat and English wheat, and fresh yeast (Saccharomyces cerevisiae) was found to be effective for developing a naturally derived product (ferment) that could be used for processing bread with the minimum use of dough improvers. The effects of ferment storage, fermentation time, and fermentation temperature on the quality of ferment and bread were evaluated to establish optimal conditions to produce a mature ferment. Trials were conducted on a pilot scale for greater relevance to industrialized bakeries. Ferment was assessed for total titratable acidity (TTA), pH, and viscosity. Breads made with ferment were evaluated for processing parameters, dough properties, and bread quality and compared to a control prepared without ferment. During fermentation, maximum TTA levels in the ferment were achieved at 100 min, then decreased by the end of fermentation, and increased by 24 h of storage at 4 °C. Viscosity was stable during fermentation but decreased by 24 h of storage. Inclusion of ferment resulted in reduced mixing times and improved dough extensibility and crumb softness. Specific loaf volume was not impacted; a slight reduction in crumb brightness and crumb structure was detected. Fermentation for 240 min at 35 °C was determined as optimal with a storage time for 24 h.

IMPROVEMENT OF FRUIT-BERRY WINE TECHNOLOГY BASED ON BIOCATALYTIC PROCESSES

In the conditions of Uzbekistan, to increase the ranгe of production of natural and environmentally friendly wine products from fruit and berry raw materials, as well as to effectively use raw materials, the production of export-oriented natural younг wines is a very urгent problem, based on the fact that the purpose of our study was to improve the existinг technoloгies in the Republic. for the production of fruit and berry wines on a biocatalytic basis, by stimulatinг zymoгenic enzymes of raw materials and yeast exohydrolases. To achieve this гoal, berries such as red cherries, strawberries, raspberries, currants and shotut were used as objects. The subject of the study was the creation of a fundamentally new technoloгy for the production of natural and export-oriented wine products from fruit and berry raw materials, as well as the research method was the determination of physicochemical, biochemical, technical and technoloгical parameters and the analysis of orгanoleptic indicators of objects by standard methods. The study showed that under an unfavorable environment, the cells of fruit and berry raw materials fall into stress as a result, under the influence of zymogenic exo- and endo enzymes of plant cells, it degrades biopolymers such as pectin and protein, which are the main components of the cytoplasmic membrane of cells, and a fundamentally new technology was developed, which allows to separate the fermentation process from the extraction of valuable components of raw materials due to the enhancement of the secondary metabolism of yeast associated with "high synthesis" in a controlled fermentation process. Moreover, in the process of carbon dioxide maceration, the yield of high-quality juice from 1 ton of raw material was increased by 10-12%, and the yield of wine material due to a decrease in yeast increased by 3.5%, due to the continuity of the process by 0.7% and the biosynthesis of ethyl alcohol was increased by 1 ÷ 1.5% vol. Natural wine products have been developed that have a pleasant harmonious taste and aroma due to their organoleptic properties.

Application and Future Prospective of Lactic Acid Bacteria as Natural Additives for Silage Production—A Review

Ensiling is one of the essential processes to preserve fodder with high nutrients and microbiological quality. The forages before ensiling have a limited number of bacteria associated with the controlled fermentation process. Undesirable microbes can grow in silages when there is not efficient fermentation. Such kinds of microbes might cause pathogenic or toxic compounds that affect animal and human health. Therefore, it is necessary to inoculate potent starter cultures. Lactic acid bacteria’s (LABs) have been considered the most prominent microbial additives used to improve the quality of silage. Currently, LABs have been used in modern and sustainable agriculture systems due to their biological potential. Recently, many scientists have increased their focus on developing nutrient-rich animal feed from forages with LAB. This current review focuses on issues related to forage preservation in the form of silages, how undesirable microbes affect the fermentation process, the critical role of LAB in silage production, and the selection of potent LABs to effectively control unwanted microbial growth and promote those which favor animal growth.

Do Kombucha Symbiotic Cultures of Bacteria and Yeast Affect Bacterial Cellulose Yield in Molasses?

Bacterial cellulose (BC) is a valuable biopolymer typically observed in Kombucha with many potential food applications. Many studies highlight yeast’s roles in providing reducing sugars, used by the bacteria to grow and produce BC. However, whether yeast could enhance the BC yields remains unclear. This study investigates the effect of yeast Dekkera bruxellensis on bacteria Komagataeibacter intermedius growth and BC production in molasses medium. The results showed that the co-culture stimulated K. intermedius by ~2 log CFU/mL, which could be attributed to enhanced reducing sugar utilization. However, BC yields decreased by ~24%, suggesting a negative impact of D. bruxellensis on BC production. In contrast to other studies, regardless of D. bruxellensis, K. intermedius increased the pH to ~9.0, favoring the BC production. Furthermore, pH increase was slower in co-culture as compared to single culture cultivation, which could be the reason for lower BC yields. This study indicates that co-culture could promote synergistic growth but results in the BC yield reduction. This knowledge can help design a more controlled fermentation process for optimum bacterial growth and, ultimately, BC production.

Model Reference Adaptive Control for Milk Fermentation in Batch Bioreactors

This paper presents the advanced control theory’s original utilisation to realise a system that controls the fermentation process in batch bioreactors. Proper fermentation control is essential for quality fermentation products and the economical operation of bioreactors. Batch bioreactors are very popular due to their simple construction. However, this simplicity presents limitations in implementing control systems that would ensure a controlled fermentation process. Batch bioreactors do not allow the inflow/outflow of substances during operation. Therefore, we have developed a control system based on a stirrer drive instead of material flow. The newly developed control system ensures tracking of the fermentation product time course to the reference trajectory by changing the stirrer’s speed. Firstly, the paper presents the derivation of the enhanced mathematical model suitable for developing a control system. A linearisation and eigenvalue analysis of this model were made. Due to the time-consuming determination of the fermentation model and the variation of the controlled plant during operation, the use of adaptive control is advantageous. Secondly, a comparison of different adaptive approaches was made. The model reference adaptive control was selected on this basis. The control theory is presented, and the control realisation described. Experimental results obtained with the laboratory batch bioreactor confirm the advantages of the proposed adaptive approach compared to the conventional PI-control.

Biogas production from the perspective of sustainable development

One of the basic aspects of sustainable development strategy involves investments in green technologies, including energy production from renewable sources. Biomass, special organic waste which belongs to “green sources” of energy can be used in the methane fermentation process of biogas production to generate heat and electricity.Biogas power plants have functioned in the Polish energy industry for many years now. On the basis of the data available from Central Statistical Office, in 2014 the ratio of biogas accounted for 7.6% of the structure of primary energy derived from renewable sources in the EU and 2.6% in Poland. An important consideration related to the production of biogas is associated with the applicability of waste resources derived from agricultural production and from the food industry, including pig slurry, slaughterhouse waste, brewing and distilling dregs as well as others. The operation of biogas plants provides considerable benefits to the environment, resulting from the controlled fermentation process and its application in the production of useful energy, as it can provide reduction of the emission of methane and other greenhouse gases. The aspects including the reduction of the volume of waste, environmental protection, fulfillment of the EU obligations and local energy security, form the reasons why communes in Poland should focus their attention on the use of biogas.This paper presents the results of SWOT analysis of biogas production in the context of sustainable development. The assessment of the aspects (strengths, weaknesses, opportunities and threats) and the intensity of their impact were undertaken on the basis of a point scale developed by the authors. The analysis shows that the process demonstrates a number of strengths, which can promote the implementation of positive changes in the environmental and social aspects undertaken on a local scale.

Safety assessment of fermented jackfruit (Artocarpus heterophyllus) pulp and leaves in Sprague-Dawley rats.

Fermented jackfruit (Artocarpus heterophyllus) extracts were produced using pure symbiotic culture of bacteria and yeast (SCOBY) under controlled fermentation process. Both female and male Sprague‐Dawley rats were orally administrated with 4,000 mg/kg of fermented jackfruit pulp and leaves extracts for 28 consecutive days. Body weight of rats was recorded at 1‐week interval until necropsy day. There was no mortality reported along the experiment with no significant differences (p > .05) record among organ histopathology and blood biochemical parameters in treated groups when compared to control group. Interestingly, there were significant differences (p < .05) in the lower body weight gained of treated rats groups as opposed to control group, indicating the potential anti‐obesity effect of fermented jackfruit extracts. In conclusion, no toxicity symptoms were observed in 28 days oral administration toxicity study of fermented jackfruit pulp and leaves extracts in Sprague‐Dawley rats for both sexes.

Design and performance of ohmic-based fermentor model for controlling fermentation process

Traditional fermentation process usually takes a long time and hard to achieve and maintain the optimum temperatures condition. The controlled fermentation process can be done using a fermentor for conditioning the temperature at the beginning of the process as bacteria and yeast can develop optimally at certain temperatures. However, traditional heaters that utilize heat transfer by conduction and convection have not been able to homogenize the temperature of products so that the fermentation process is not well controlled. Heating technology that has great potential to produce fast and uniform heating is by using ohmic technology. This research aims to design and to conduct a test of ohmic-based fermentor model. Methods used in this study were a functional and structural analysis of fermentor design and performance test of the fermentor model. The test was conducted using two materials as the heated product (0.02 M NaCl solution as a liquid product and soybean as a non-liquid product) with three variations of voltage treatment (110, 165, and 220 V). Design of the ohmic-based fermentor model had been constructed and tested. Analysis of alternative methods, types, and ohmic fermentor material has been carried out as a reference in designing. Test results showed that the fermentor had been proven to be able to maintain, control, and monitor the temperature in the reactor in real-time. The energy efficiency achieved a high value of 81.96% up to 86.29%. The temperature distribution in the fermentor was also determined uniform for both liquid and non-liquid products with the average value of 40.01±0.16°C (the reference temperature is 40°C). It was indicated that the fermentor model can be used for further fermentation test using various products.

Evaluation of multi-starter S. cerevisiae/ D. bruxellensis cultures for mimicking and accelerating transformations occurring during barrel ageing of beer

During beer ageing, endogenous barrel microbes grow spontaneously and transform wort/beer composition, being Dekkera bruxellensis and Saccharomyces cerevisiae among the main contributors to the chemical and sensory profile of aged beer. This work aims at the application of multi-starter cultures to mimic and accelerate biological modifications occurring during barrel ageing of beer, in controlled fermentation processes. Co-cultures of D.bruxellensis/S.cerevisiae were conducted under conditions commonly found in barrel aged beer production: different pitching rates, high glucose concentration and presence of ethanol and wood extracts. Selective pressures and competition between yeasts influenced microbial growth and metabolite production, namely ethanol, acetic acid and target volatile compounds (esters, alcohols, terpenols, volatile acids and volatile phenols). Metabolic profiles of co-cultures combined traits of both species, and differed from those of pure cultures. Lastly, multi-starters were successfully applied in combination with wood in a controlled and accelerated fermentation process for mimicking barrel ageing transformations.

High-Throughput Illumina MiSeq Amplicon Sequencing of Yeast Communities Associated With Indigenous Dairy Products From Republics of Benin and Niger.

Traditional Wagashi cheese and fermented cow milk are among the most popular dairy products appreciated by people from Benin, Niger, and the neighboring region. These products are the main source of protein in the diet of the low-income population in the region. The fermented milk is prepared by spontaneous fermentation without back-slopping. Whereas, the leaf extract of Calotropis procera is used for curdling the milk to prepare the soft Wagashi cheese. The present study aims to provide in-depth analysis of yeast communities associated with these traditional milk products by high-throughput Illumina MiSeq amplicon sequencing of internal transcribed spacer (ITS) region of fungal rRNA genes. A total of 60 samples, 20 samples of fermented milk each from Benin and Niger, and 20 samples of Wagashi cheese from Benin were used for analysis. The metagenomic investigation revealed that Kluyveromyces marxianus, Saccharomyces cerevisiae, Candida parapsilosis, and Sagenomella keratitidis were the predominant yeast species present in the traditional milk products. Furthermore, we noticed a high presence of K. marxianus (61.1% relative abundance) in the Wagashi cheese and S. cerevisiae (28.4% relative abundance) in the fermented milk of Niger. The presence of potential pathogenic yeast C. parapsilosis and S. keratitidis in these African milk products calls for further investigation to assess their safety. The predominant yeast K. marxianus and S. cerevisiae, recognized with generally regarded as safe (GRAS) status, could be further selected as starter culture along with lactic acid bacteria for developing controlled fermentation processes with enhanced product quality and safety.

Preservative and Irritant Capacity of Biosurfactants From Different Sources: A Comparative Study

One of the most important challenges for pharmaceutical and cosmetic industries is solubilization and preservation of their active ingredients. Therefore, most of these formulations contain irritant chemical additives to improve their shelf-life and the solubility of hydrophobic ingredients. An interesting alternative to chemical surfactants and preservatives is the use of biosurfactants; thus, their surfactant properties and composition make them more biocompatible than their chemical counterparts. Moreover, some biosurfactants have shown antimicrobial activity in addition to their detergent capacity. In this work, the antimicrobial and irritant effect of 2 biosurfactant extracts was studied: one produced in a controlled fermentation process with Lactobacillus pentosus and the other produced from corn stream by spontaneous fermentation. The results showed a strong antimicrobial activity of the biosurfactant extract obtained from corn stream on pathogenic bacteria, in comparison with the L. pentosus biosurfactant extract. Moreover, both biosurfactants did not produce any irritant effect on the chorioallantoic membrane of hen's egg assay contrary to sodium dodecyl sulfate. This is the first study dealing with the application of biosurfactant extracts on sensitive biological membranes, and this is the first time that the preservative capacity of a biosurfactant extract obtained in spontaneous fermentation is being evaluated, achieving promising results.

Mathematical modelling of ethanol production as a function of temperature during lactic-alcoholic fermentation of goat’s milk after hydrolysis and transgalactosylation of lactose

Kefir prepared from goat’s milk after enzymatic lactose bioconversion is a novel and increasingly popular milk product. During the production of kefir, fermentation conditions must be selected to ensure the final product is consistently of the same quality, as the most important feature of the drink is the ethanol content. The aim of the work described in this paper was the development of a mathematical model that could describe the dynamic process of ethanol production during kefir fermentation of lactose-free goat’s milk after enzymatic synthesis of galactooligosaccharides (GOS). Mathematical parameters of the equation used were given a biological significance, these parameters were defined with appropriate functions, in which temperature was taken as the dependent variable. We have created a model to enable a controlled fermentation process. Parameterization of the kinetics of the synthesis of ethanol in goat’s milk after hydrolysis and transgalactosylation of lactose allows production with reproducible quality control.