Fermentation Tank Research Articles

Fermentation of Saccharomyces cerevisiae in a 7.5 L ultrasound-enhanced fermenter: Effect of sonication conditions on ethanol production, intracellular Ca2+ concentration and key regulating enzyme activity in glycolysis

In this study, the effect of sonication on the fermentation process of a single-celled fungus was examined. During the experiment, Saccharomyces cerevisiae (S. cerevisiae) was used as the starting strain for ethanol fermentation (batch fermentation) in a 7.5 L automated fermentation tank. The fermentation tank connected with a six-frequency ultrasonic equipment. Non-sonication treatment was set up as the control. Sonication treatment with power density of 280 W/L and 48 h of treatment time were set up as trial groups for investigating the influence of different ultrasound frequency including 20, 23, 25, 28, 33 and 40 kHz on the changes in dry cell-weight, glucose consumption rate, and ethanol yield. The results showed that the dry cell-weight, glucose consumption rate, and ethanol content reached the best results under the ultrasonic condition of 28 kHz ultrasound frequency in comparison with other ultrasound frequency. The dry cell-weight and ethanol content of the 28 kHz ultrasonic treatment group increased by 17.30% and 30.79%, respectively in comparison with the control group The residual sugar content dropped to a lower level within 24 h, which was consistent with the change in ethanol production. Besides, the results found that the glucose consumption rate increased compared to the control. It indicated that ultrasound accelerated glucose consumption contributed to increase the rate of ethanol output. In order to explore the mechanism of sonication enhanced the content of ethanol output by S. cerevisiae, the morphology, permeability of S. cerevisiae and key enzyme activities of ethanol synthesis were investigated before and after sonication treatment. The results showed that after sonication treatment, the extracellular nucleic acid protein content and intracellular Ca2+ concentration increased significantly. The morphology of S. cerevisiae was observed by SEM and found that the surface of the strain had wrinkles and depressions after ultrasonic treatment. furthermore after sonication treatment, the activities of three key enzymes which catalyze three irreversible reactions in glycolysis metabolism, namely, hexokinase, phosphofructokinase and pyruvate kinase increased by 59.02%, 109.05% and 87.27%, respectively. In a word, low-intensity ultrasound enhance the rate of ethanol output by S. cerevisiae might due to enhancing the growth and cell permeability of strains, and increasing the activities of three key enzymes of ethanol biosynthesis.

Difference between the cell wall roughnesses of mothers and daughters of Saccharomyces cerevisiae subjected to high pressure stress

High hydrostatic pressure (HHP) stress generates cellular responses similar to those to other stresses that yeasts endure in fermentation tanks. Structural and spatial compaction of molecules, as well as weakening and stretching of plasma membranes and cell walls, are often observed and have a significant influence on the fermentative process. Atomic force microscopy (AFM) yields accurate data on the morphological characteristics of yeast cell walls, providing important insights for the development of more productive yeast strains. Saccharomyces cerevisiae cell wall assessment using AFM in the intermittent contact reading mode using a silicon cantilever, before and after application of a pressure of 100 MPa for 30 min, demonstrated that mother and daughter cells have different responses. Daughter cells were more sensitive to the effects of HHP, presenting lower average Ra (arithmetic roughness), Rz (ten-point average roughness), and Rq (root-mean-square roughness) after exposure to high pressure. Better adaptation to stress in mother cells leads to higher cell wall resistance and, therefore, to better protection.

PROTOTYPE ALAT FERMENTOR STATER MODIFIED CASSAVA FLOUR MENGGUNAKAN METODE FUZZY MAMDANI

Stater MOCAF is a seed fermented during the manufacture of biologically modified MOCAF. The manufacture of MOCAF stater tools can help MOCAF flour entrepreneurs to use automated tools in producing staters. The design used the Arduino Mega2560 as a microcontroller to control the fermentation tank system. Temperature parameters in the heater are used to stabilize the temperature with a set point of 370C. As for the set point pH 5.5. Use citric acid for acidic liquids, and use water pH 8+ for alkaline solutions. The bacteria used to make mocaf staters is lactobacillus plantarum.
 The first test was to test the PWM PG45 motor, which is used to drive a mixer in the form of a duty cycle. Sensor testing includes DS18B20 waterproof temperature sensor testing and pH sensor testing. In addition, the Fuzzy Mamdani method is used to test the tool as a whole. This fuzzy control is used to control the temperature and pH value of the MOCAF fermentor. If the temperature and pH values do not match the required parameters, then there are temperature actuators and pH actuators to stabilize the parameters. Fermentation is carried out for 24 hours, and the temperature and pH value are controlled to remain stable at 370C and the pH range of 4-6. After about 4 hours of measurement, the new temperature drops. However, after 10 minutes, the temperature stabilizes at 370C. As for the pH value, because the pH sensor reading response is about 2 minutes then the value will change.

Development of a portable electronic nose for in‐situ detection of submerged fermentation of Tremella aurantialba

AbstractThe aim of this study was to develop a portable electronic nose (e‐nose) system for the rapid and convenient detection of saponin in submerged fermentation of Tremella aurantialba (T. aurantialba) in situ. The system was built using hardware and software systems. The hardware system consisted of a gas path module and a circuit module, and the software framework provided a friendly human–computer interface and multivariate computational tools. Subsequently, the e‐nose system was used to detect off‐gas in fermentation tanks every 12 hr in situ. Saponin content was simultaneously determined by the traditional measurement method. On the basis of odor data from the e‐nose, partial least squares regression (PLSR) was used to establish a quantitative model for the prediction of saponin content. For the PLSR model, the root mean square error of prediction (RMSEP) was 0.2247 and the correlation coefficients of prediction (Rp) were 96.76% in the prediction set. These results showed that the feasibility of the device designed to detect the fermentation degree of the process and proved to be a valuable tool for real‐time and in‐situ detection of the fermentation process of T. aurantialba.

Machine-learning classification of environmental conditions inside a tank by analyzing radar curves in industrial level measurements

There are several solutions to measure the tank level in industrial applications. However, the environmental conditions inside this tank, such as turbulence and foam, can jeopardize measurement accuracy and precision. This article proposes a methodology to identify the presence of turbulence and foam in a fermentation tank. The proposal is based on the extraction, selection, and classification of statistical features by machine learning methods. The use of machine learning strategies and statistical features guarantees the necessary robustness and generality for industrial applications. Actual data obtained from a must fermentation tank of a sugar-alcohol industrial plant were used for training and verifying one Artificial Neural Network-based and three Support Vector Machine-based classifiers. These classifiers obtained accuracy over 98% for different environmental conditions proving the effectiveness of the proposed methodology.

Use of metabarcoding and source tracking to identify desirable or spoilage autochthonous microorganism sources during black olive fermentations

This study aimed at investigating the influence of the process environment and raw materials as sources of microorganisms during Nyons black table olive fermentations. Fermented olives and/or brine from spoiled fermentation tanks were analyzed and compared to good quality samples from fermentations collected during 3 consecutive harvest years. Fresh olives, salt and different process environment samples were also analyzed. Microbial diversity of all samples was analyzed using 16S and ITS2 amplicon sequencing and SourceTracker tool was used to investigate links between environment, raw materials and fermentation samples. First, comparison of microbial diversity in control and most spoiled fermentations revealed striking differences in bacterial composition with an overall higher diversity in spoiled fermentations especially for lactic acid bacteria with Lentilactobacillus buchneri, Lentilactobacillus parafarraginis dominating in brine and Pediococcus parvulus, Pediococcus ethanolidurans dominating in olive fruits. Fungal communities were similar in composition although higher abundances of Pichia membranifaciens and Penicillium carneum/roqueforti were observed in spoiled samples. Secondly, process environment samples were characterized by high bacterial and fungal diversity, especially compared to fresh olive fruits. Overall, dominant fungal species in control fermentations were also found in most environmental samples revealing a “house mycobiota”. SourceTracker analysis further highlighted the contribution of brine and water from the optical sorter as a source of fungi. Most interestingly, spoilage fungi and most bacteria were retrieved in brine and environmental samples while others such as P. ethanolidurans were only found in environmental samples indicating that the studied spoilage originated from a fermentation deviation rather than a punctual contamination. Taken altogether, these results highlighted the positive and negative influence of the process environment and emphasized the relevance of studying it to better understand microbial vectors occurring during food fermentations, especially natural ones.

Comprehensive review on agricultural waste utilization and high-temperature fermentation and composting

Due to the high demand for food and meat for the world's growing population, the agricultural sector is expanding every year. Timely and effective treatment is of utmost importance to utilize organic matter in agricultural waste and avoid environmental pollution. Composting or aerobic fermentation is an effective way to treat agricultural waste and produce organic fertilizer. Improving the application rate of organic fertilizer in soil needs time to reduce dependence on chemical fertilizers. This review article presented the current status and traditional agricultural waste (livestock manure and crop straws) utilization methods, the art of aerobic fermentation process including ultrahigh temperature fermentation and composting. The selection of livestock manure and crop straws as agricultural waste for this review article is due to high nutrients contents and massive generation of them worldwide. This article also included the development of aerobic fermentation technology and listed the high-temperature fermentation tanks. Based on high-temperature aerobic fermentation process performance and quality compost production, recently, some researchers have started working on hyperthermophile pretreatment-assisted high temperature composting, also discussed. Finally, this article gave brief knowledge about compost maturity, which is very important to measure before its application as an organic fertilizer. This art of literature could provide comprehensive knowledge about agricultural waste utilization and high-temperature composting to researchers.

INVESTIGATION OF FERMENTATION CONDITION FOR PRODUCTION ENHANCEMENT OF POLYHYDROXYALKANOATE FROM CHEESE WHEY BY PSEUDOMONAS SP.

A newly acquired polyhydroxyalkanoate (PHA) producing Pseudomonas sp. was characterized based on 16S rRNA gene sequences (1,423 bp) and identified as P. Putida SS9. This strain P. putida SS9 was considered in respect of its potential for achieving maximum production of PHA under controlled volumetric oxygen transfer coefficient (kLa) using inexpensive substrate, cheese whey. The significant parameters such as pH, temperature, nitrogen source concentration were studied in shake flask. The influence of aeration and agitation on kLa and production of PHA was studied in stirred tank fermenter. Maximum PHA concentration of 5.98 and 4.33 g/l was obtained using cheese whey medium (CWM) and mineral salts medium (MSM) respectively. Further, the properties of PHA were analyzed by Differential scanning calorimetry, Thermal gravimetry analysis. The structure of the compound was elucidated by Fourier transform infrared and Nuclear magnetic resonance spectroscopy. The findings suggested that the cheese whey could be a most excellent alternative carbon source for PHA production using P. putida SS9 and thus it could effectively replace the synthetic mineral salts medium under optimum kLa. The nucleotide sequence proclaimed in this work will emerge in the GenBank nucleotide sequence database under accession number MF403057.

Increasing glycolysis by deletion of kcs1 and arg82 improved S-adenosyl-l-methionine production in Saccharomyces cerevisiae

Reprogramming glycolysis for directing glycolytic metabolites to a specific metabolic pathway is expected to be useful for increasing microbial production of certain metabolites, such as amino acids, lipids or considerable secondary metabolites. In this report, a strategy of increasing glycolysis by altering the metabolism of inositol pyrophosphates (IPs) for improving the production of S-adenosyl-l-methionine (SAM) for diverse pharmaceutical applications in yeast is presented. The genes associated with the metabolism of IPs, arg82, ipk1 and kcs1, were deleted, respectively, in the yeast strain Saccharomyces cerevisiae CGMCC 2842. It was observed that the deletions of kcs1 and arg82 increased SAM by 83.3 % and 31.8 %, respectively, compared to that of the control. In addition to the improved transcription levels of various glycolytic genes and activities of the relative enzymes, the levels of glycolytic intermediates and ATP were also enhanced. To further confirm the feasibility, the kcs1 was deleted in the high SAM-producing strain Ymls1ΔGAPmK which was deleted malate synthase gene mls1 and co-expressed the Acetyl-CoA synthase gene acs2 and the SAM synthase gene metK1 from Leishmania infantum, to obtain the recombinant strain Ymls1Δkcs1ΔGAPmK. The level of SAM in Ymls1Δkcs1ΔGAPmK reached 2.89 g L−1 in a 250-mL flask and 8.86 g L−1 in a 10-L fermentation tank, increasing 30.2 % and 46.2 %, respectively, compared to those levels in Ymls1ΔGAPmK. The strategy of increasing glycolysis by deletion of kcs1 and arg82 improved SAM production in yeast.

Facility‐specific ‘house’ microbiome ensures the maintenance of functional microbial communities into coffee beans fermentation: implications for source tracking

This work aimed at studying the unconfirmed hypothesis predicting the existence of a connection between coffee farm microbiome and the resulting spontaneous fermentation process. Using Illumina-based amplicon sequencing, 360 prokaryotes and 397 eukaryotes were identified from coffee fruits and leaves, over-ripe fruits, water used for coffee de-pulping, depulped coffee beans, soil, and temporal fermentation samples at an experimental farm in Honduras. Coffee fruits and leaves were mainly associated with high incidence of Enterobacteriaceae, Pseudomonas, Colletotrichum, and Cladosporium. The proportion of Enterobacteriaceae was increased when leaves and fruits were collected on the ground compared to those from the coffee tree. Coffee farm soil showed the richest microbial diversity with marked presence of Bacillus. Following the fermentation process, microorganisms present in depulped coffee beans (Leuconostoc, Gluconobater, Pichia, Hanseniaspora, and Candida) represented more than 90% of the total microbial community, which produced lactic acid, ethanol, and several volatile compounds. The community ecology connections described in this study showed that coffee fruit provides beneficial microorganisms for the fermentation process. Enterobacteria, Colletotrichum, and other microbial groups present in leaves, fruit surface, over-ripe fruits, and soil may transfer unwanted aromas to coffee beans, so they should be avoided from having access to the fermentation tank.

Study on the Extraction Technology of Candida antarctica Lipase B by Foam Separation

Candida antarctica Lipase B (CALB) has a wide range of applications in many fields. In this study, Pichia pastoris was used to express CALB for fermentation tank culture. Sodium dodecyl sulfate (SDS) was used as a surfactant, and foam separation technology was used to explore the best experimental conditions for the harvest of CALB. The results showed that the optimal technological conditions for the foam separation and recovery of CALB were as follows: liquid volume was 150 mL, separating gas velocity was 600 mL/min, pH value was 7, and surfactant SDS concentration was 0.5 mg/mL. Under these conditions, the enrichment ratio of CALB was 0.95, and recovery rate R was 80.32%, respectively, indicating that the foam separation technology is feasible to extract lipase B.

Optimal production planning and scheduling in breweries

This work considers the optimal production planning and scheduling problem in beer production facilities. The underlying optimization problem is characterized by significant complexity, including multiple production stages, several processing units, shared resources, tight design and operating constraints and intermediate and final products. Breweries are mainly differentiated to the rest of the beverage industries in terms of long lead times required for the fermentation/maturation process of beer. Therefore, synchronizing the production stages is an extremely challenging task, while the long time horizon leads to larger and more difficult optimization problems. In this work we present a new MILP model, using a mixed discrete-continuous time representation and the immediate precedence framework in order to minimize total production costs. A number of test cases are used to illustrate the superiority of the proposed model in terms of computational efficiency and solution quality compared with approaches developed in other research contributions. The proposed model provides consistently better solutions and improvements of up to 50% are reported. In order to address large-scale problem instances and satisfy the computation limitations imposed by the industry, a novel MILP-based solution strategy is developed, that consists of a constructive and an improvement step. As a result, near-optimal solutions for extremely large cases consisting of up to 30 fermentation tanks, 5 filling lines and 40 products are generated in less than two hours. Finally, the proposed method is successfully applied to a real-life case study provided by a Greek brewery and near-optimal schedules are generated in relatively short CPU times.

Polyphenolic Composition and In Vitro Antioxidant Activity of Red Grape Seeds as Byproducts of Short and Medium-Long Fermentative Macerations.

The polyphenolic composition and antioxidant activity of grape seeds, as byproducts of red winemaking, depend on various factors, such as grape cultivar, vintage effect, grape maturity and winemaking methods. In the present work, the influence of the maceration length on the polyphenolic and antioxidant characteristics of the seeds of four Italian red grape cultivars (‘Barbera’, ‘Grignolino’, ‘Nebbiolo’, and ‘Uvalino’), sampled from the fermentation tanks after short (two days) and medium-long (7–21 days) macerations, was studied with spectrophotometric methods, high-performance liquid chromatography (HPLC), and three different antioxidant assays (2,2′-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), ferric reducing antioxidant power (FRAP) and 2,2 diphenyl-1-picrylhydrazyl (DPPH)). The total polyphenolic content (gallic acid equivalent (GAE)) of the seeds sampled after short macerations ranged between 24.5 and 60.1 mg/g dry weight (DW), and it dropped to 20.0–37.5 mg/g DW after medium-long macerations. The polyphenolic profile of the shortly macerated seeds was related to the varietal characteristics, while, after longer macerations, the influence of the maceration length prevailed on the cultivar effect. The multiple in vitro antioxidant activity tests (ABTS, FRAP and DPPH), although based on different mechanisms capable of highlighting behavioral differences between the different polyphenolic compounds, were highly correlated with each other and with the polyphenolic parameters; the qualitative differences between the matrices in the polyphenolic profile were probably less important than the quantitative differences in the polyphenolic content. The relations with the polyphenolic content were linear, except for the Efficient Concentration (EC20) parameter, whose relation was better described by a hyperbolic equation.

Vibrations as a cause of texture defects during yogurt manufacturing – Formation of vibrations and their propagation in dairy production lines

Abstract Vibrations during the fermentation of yogurt and related milk products have recently been reported to disturb the gelation and result in quality defects such as particle formation, graininess, and syneresis. However, primary research on this topic was focused on experiments performed on a laboratory and pilot-plant scale. In this study, three large dairy factories were visited, and yogurt samples were directly taken out of various fermentation tanks, showing great differences in terms of graininess and particle content. Thereupon, vibration measurements were conducted at three industrial yogurt plants. Particularly, pumps and their influence on the vibrational excitation of the fermentation tanks were examined. The major structural and mechanical differences of these plants, such as distances between the vibration source and the tank or the types of pumps used, led to varying vibrational states at the fermentation tanks. We concluded that the vibrational excitation of each plant must be evaluated individually in order to estimate the potential for vibration-induced texture defects.

하수슬러지 Bio-drying 시 발효조 온도와 수분 저감과의 관련성 연구

Since sewage sludge has a high moisture content even after dehydration, when used as energy such as fuel, the moisture content of sewage sludge must be reduced to 10% or less. In the case of using sewage sludge as fuel or reducing moisture, a fermentation and drying system by Bio-drying is introduced, and the Bio-drying system is generally dried by heat generated when aerobic microorganisms decompose organic matter in the sewage sludge, and the correlation between the temperature change and the water reduction of the fermentation tank is determined to be very important. The reduction of sewage sludge moisture by the bio-drying system was found to be most affected by the number of stirrings in the fermentation tank and the maintenance of high temperatures of 70oC or higher, and the reduction of temperature caused by excessive supply of air at 390 to 600mL/kg/min was found. In the case of experiments with one to five times more stirring times, the moisture reduction effect was 14.5% and 15.5%, which showed much greater reduction rate than the average reduction rate of 12.7%.

Production of Neoagaro-Oligosaccharides With Various Degrees of Polymerization by Using a Truncated Marine Agarase.

Bioactivities, such as freshness maintenance, whitening, and prebiotics, of marine neoagaro-oligosaccharides (NAOS) with 4–12 degrees of polymerization (DPs) have been proven. However, NAOS produced by most marine β-agarases always possess low DPs (≤6) and limited categories; thus, a strategy that can efficiently produce NAOS especially with various DPs ≥8 must be developed. In this study, 60 amino acid residues with no functional annotation result were removed from the C-terminal of agarase AgaM1, and truncated recombinant AgaM1 (trAgaM1) was found to have the ability to produce NAOS with various DPs (4–12) under certain conditions. The catalytic efficiency and stability of trAgaM1 were obviously lower than the wild type (rAgaM1), which probably endowed trAgaM1 with the ability to produce NAOS with various DPs. The optimum conditions for various NAOS production included mixing 1% agarose (w/v) with 10.26 U/ml trAgaM1 and incubating the mixture at 50°C in deionized water for 100 min. This strategy produced neoagarotetraose (NA4), neoagarohexaose (NA6), neoagarooctaose (NA8), neoagarodecaose (NA10), and neoagarododecaose (NA12) at final concentrations of 0.15, 1.53, 1.53, 3.02, and 3.02 g/L, respectively. The NAOS served as end-products of the reaction. The conditions for trAgaM1 expression in a shake flask and 5 L fermentation tank were optimized, and the yields of trAgaM1 increased by 56- and 842-fold compared with those before optimization, respectively. This study provides numerous substrate sources for production and activity tests of NAOS with high DPs and offers a foundation for large-scale production of NAOS with various DPs at a low cost.

Stimulation of in situ low intensity ultrasound on batch fermentation of Saccharomyces cerevisiae to enhance the GSH yield

AbstractIn this study, an in situ 7.5 L ultrasonic fermentation tank was used to culture Saccharomyces cerevisiae at 30°C for 36 hr to explore the effects of low intensity ultrasound on the production of glutathione (GSH). Ultrasonic conditions of 28 kHz frequency, 28 W/L power density for fermentation time of 0–12 hr, 280 W/L power density for fermentation time of 12–36 hr, 3 s of interval and fixed frequency mode were used for the set‐up and a nonsonicated set‐up served as the control for the experiment. Results showed that ultrasound treatment increased total GSH production by 15.60% from a maximum value of 45.52 mg/L in the control to a maximum value of 52.62 mg/L in the sonicated sample. Also, intracellular and extracellular GSH productions in the sonicated sample increased by 5.60% and 42.92% respectively. Regular detection of the changes of biomass yield, residual sugar, dissolved oxygen and pH showed that sonication resulted in biomass increased by 7.25%, glucose consumption rate increased by 53.08% and dissolved oxygen content decreased by 41.67%. The biomass models of sonication and nonsonication treatments were established according to growth of S. cerevisiae showed that the model fitted well with Logistic regression in which the strain specific growth rate increased by 60.95% after sonication. GSH production model agreed with Luedeking‐Piret regression in which GSH synthesis parameters of sonication, α and β increased by 1.96% and 19.64% in comparison to the nonsonicated sample. This study clearly demonstrated that ultrasonic stimulation could improve the biosynthesis of GSH during fermentation.Practical ApplicationsIn this study, the GSH was producted by microbial fermentation in in situ 7.5 L ultrasonic fermentation tank. During the fermentation, sonication was applied to increasing yield of GSH. The results show that the study provides a theoretical basis for manufacture GSH combined with sonication industrialization. The fermentation kinetic model was established, which provided experimental basis for continous fermentation.

Intensive Multiple Sequential Batch Simultaneous Saccharification and Cultivation of Kluyveromyces marxianus SS106 Thermotolerant Yeast Strain for Single-Step Ethanol Fermentation from Raw Cassava Starch

We developed the intensive multiple sequential batch simultaneous saccharification and cultivation of the selected thermotolerant yeast strain for single-step ethanol production. The selection and high-cell-density inoculum production of thermotolerant yeast able to produce ethanol under the optimal conditions for single-step ethanol fermentation has become a necessity. In this study, the newly isolated Kluyveromyces marxianus SS106 could tolerate high temperatures (35–45 °C) and grow under a wide range of pH values (3.0–5.5), which are the optimum conditions of raw cassava starch hydrolyzing enzyme used in single-step ethanol fermentation. The high-cell-density concentration of K. marxianus SS106 was produced by a single batch and an intensive multiple sequential batch process in a 5-L stirred tank bioreactor using the simultaneous saccharification and cultivation (SSC) method. The single SSC process yielded the yeast cell biomass at a concentration of 39.30 g/L with a productivity of 3.28 g/L/h and a specific growth rate of 0.49 h−1. However, the yeast cell density concentration was higher in the intensive multiple sequential batch SSC than in the single batch process. This process yielded yeast cell biomass at concentrations of 36.09–45.82 g/L with productivities of 3.01–3.82 g/L/h and specific growth rates of 0.29–0.44 h−1 in the first six batch cycle. The results suggested that the intensive multiple sequential batch simultaneous saccharification and cultivation of K. marxianus SS106 would be a promising process for high-cell-density yeast production for use as the inoculum in single-step ethanol fermentation. Furthermore, we also experimented with single-step ethanol production from raw cassava starch by K. marxianus SS106 in a 5-L stirred tank fermenter. This produced ethanol at a concentration of 61.72 g/L with a productivity of 0.86 g/L/h.

Data science-based modeling of the lysine fermentation process

Mathematical modeling of the fermentation process is useful for understanding the influence of operating parameters on target production and control performance, depending on the situation, to stabilize the target production at a high-level. However, the previous approaches using physical modeling methods and traditional knowledge-based methods are difficult to apply on working fermentors at a commercial plant scale because they have unknown and unmeasured parameters involved in target production. This study focused on developing an ensemble learning model that can predict the amino acid fermentation process behavior based on observation values, which can be obtained from fermentation tanks and future control input. The results revealed the influence of each control input on lysine production during the culturing period. Furthermore, high-order stability, which achieved the target trajectory for lysine production, was realized using dynamic fermentation controls. Additionally, this study demonstrates that the fermentation behavior on a commercial plant scale is reproduced using the ensemble device. The ensemble learning model will provide novel control system with data-science based model of Industry 4.0 in the field of biotechnological processes.

Vibrations as a cause of texture defects during the acid-induced coagulation of milk – Fluid dynamic effects and their impact on physical properties of stirred yogurt

Abstract Vibrations during yogurt fermentation have been reported to disturb the gelation by inducing large, visible particles. Such vibrations are generated by the machinery used for the industrial manufacture and can cause structural excitation of the fermentation tanks. To study the effect of vibrations on yogurt structure, an experimental setup was constructed consisting of a cylindrical tank (height: 600 mm). The bottom of the tank was excited by a shaker, resulting in a vertical vibration propagation. Skim milk was vibrated during fermentation at 30 Hz and different amplitudes. Vibrated gels showed syneresis up to ∼5%. Samples were taken at different height positions of the fermenter, processed into stirred yogurt, and analyzed. The number of large particles was primarily related to the set vibration amplitude, however, particle formation was more pronounced in the lower and upper area. Yogurts with a high particle number exhibited a reduced water-holding capacity and apparent viscosity. Moreover, the fluid dynamic effects of vibrations were investigated by particle image velocimetry. Vibrations led to uniform to-and-fro motions, whereas chaotic flow was observed at the surface. Finally, the impact of vibrations on the gelation mechanism is discussed.