Optimization of riboflavin production by recombinant Bacillus subtilis RH44 using statistical designs

Intelligent biomanufacturing of water-soluble vitamins

Given the crucial role of water-soluble vitamins in the human body and the rising demand for natural sources, their biosynthesis has gained the attention of researchers. This review offers a comprehensive look at recent progress in water-soluble vitamin biosynthesis, emphasizing synthetic biotechnology for green biomanufacturing. Specifically, it encompasses the optimization of biological components, pathways, and systems, as well as energy metabolism regulation, stress-tolerance enhancement, high-throughput screening, and the upscaling of production processes. It also envisages intelligent biomanufacturing platforms, highlighting the role of systems biology and artificial intelligence (AI), and proposes future research directions, such as integrating AI-driven metabolic models, enzyme engineering, and cell-free systems, to address limitations in the efficiency, toxicity, and scalability of water-soluble vitamin production.

Response surface analysis and kinetics modelling of the exopolysaccharide production by probiotic Lactiplantibacillus plantarum HMX2

Exopolysaccharides (EPSs) produced by lactic acid bacteria have been widely studied, but their applications as important functional biopolymers are limited due to the low level of EPS production. In this study, Lactiplantibacillus plantarum HMX2 was shown with high capacity of EPS production with a maximum yield of 556.43 mg/L under the optimized fermentation conditions with 27.57 g/L of soy peptone, 20 g/L of sucrose, 4 % (v/v) of inoculum, the initial medium pH 6.4, and fermentation temperature at 34.5 °C for 10 h. The response surface analysis indicated significant interactions between the fermentation conditions, i.e. the initial medium pH vs. fermentation temperature or soy peptone content, which jointly promoted the EPS production by HMX2. The kinetics models for the bacterial growth, EPS synthesis and sucrose consumption during the fermentation under the optimized conditions were established by using Logistic and Boltzmann models. There were good fitting of the models for the experimental results with the relative errors lower than 15 % and correlation coefficients (R2) of higher than 0.99. The results of this study provide basic theoretical support by modelling the fermentation kinetics for efficient production of the EPS by HMX2 and its potential application in functional foods.

Riboflavin overproduction from diverse feedstocks with engineeredCorynebacterium glutamicum

Riboflavin overproduction byCorynebacterium glutamicumwas achieved by screening synthetic operons, enabling fine-tuned expression of the riboflavin biosynthetic genesribGCAH.The synthetic operons were designed by means of predicted translational initiation rates of each open reading frame, with the best-performing selection enabling riboflavin overproduction without negatively affecting cell growth. Overexpression of the fructose-1,6-bisphosphatase (fbp) and 5-phosphoribosyl 1-pyrophosphate aminotransferase (purF) encoding genes was then done to redirect the metabolic flux towards the riboflavin precursors. The resulting strain produced 8.3 g l-1of riboflavin in glucose-based fed-batch fermentations, which is the highest reported riboflavin titer withC. glutamicum. Further genetic engineering enabled both xylose and mannitol utilization byC. glutamicum, and we demonstrated riboflavin overproduction with the xylose-rich feedstocks rice husk hydrolysate and spent sulfite liquor, and the mannitol-rich feedstock brown seaweed hydrolysate. Remarkably, rice husk hydrolysate provided 30% higher riboflavin yields compared to glucose in the bioreactors.

Microbial diversity, culture conditions, and application effect of YSJ: A composite microbial system for degradation of Yanshan ginger branches and leaves

BACKGROUND

Yanshan ginger (Alpinia zerumbet) is a perennial herb used as a medicine and spice, and is beneficial for soil and water conservation in karst areas. Given the widespread utilization of Yanshan ginger in China and continuing expansion of the planting area, disposal of waste materials is problematic. The branches and leaves of Yanshan ginger contain a variety of potent antibacterial compounds, such as volatile oils, phenols, and diterpenoids, which hinder their rapid degradation by microorganisms. In this study, we screened and constructed a composite microbial system to provide a technical reference for production of organic fertilizer from the branches and leaves of Yanshan ginger.

METHODS

A composite microbial system, "YanShan Jun" (YSJ), was developed by screening for efficient detoxification and degradation of the branches and leaves of Yanshan ginger. High-throughput sequencing technology was used to investigate the stability and diversity of YSJ subcultures. The culture conditions for YSJ were optimized by sequential single-factor experiments and response surface analysis. Yanshan ginger leaves and branches were inoculated with YSJ to study its effects on composting efficiency.

RESULTS

The microbial composition of YSJ was stable and rich in diversity through continuous subculture. Through response surface analysis, the optimized culture conditions for YSJ were determined as follows: peptone 8.0 g/L, sodium chloride 9.0 g/L, calcium carbonate 5.2 g/L, yeast powder 1.6 g/L, cultivation temperature 56.1°C, and culture duration 6 d. Under these conditions, the degradation rate of Yanshan ginger was 58.32%, which was 14.22% higher than that before optimization. The ability of YSJ to degrade the antibacterial compounds of ginger after optimization was significantly enhanced. Inoculation of Yanshan ginger compost with YSJ increased the fermentation temperature, prolonged the high-temperature period, and reduced the water content and pH of the compost in the early stage.

CONCLUSIONS

Inoculation of plant compost with YSJ bacteria improves the nutritional environment of the compost, promotes the composting reaction, promotes the rapid formation of a strong indigenous microflora, forms a beneficial microecological environment, and increases the composting efficiency. This study provides a theoretical basis for practical application of YSJ for organic fertilizer production from Yanshan ginger.

A statistical optimization by response surface methodology for the enhanced production of riboflavin from Lactobacillus plantarum–HDS27: A strain isolated from bovine milk

In the present study, Lactobacillus plantarum-HDS27 strain isolated from bovine milk was used for the enhanced production of riboflavin. Production medium was optimized by one factor at a time with different parameters. Statistical optimization by Response surface methodology (RSM), central composite design was used to optimize variables such as pH, temperature, glucose, and yeast extract. The present study reveals the maximum riboflavin production by one factor at a time was obtained under the culture conditions; glucose, yeast extract, pH 6, the temperature at 40°C, and 3% of inoculum size. In RSM, analysis of variance for the responses was calculated. Among the tested variables, pH, yeast extract, and temperature showed significant impact on riboflavin production. Maximum amount of yeast extract in production medium resulted in increased riboflavin production. The riboflavin production after 24 h with the optimal condition was found to be 12.33 mg/L. It was found proximate to the expected value (12.29 mg/L) achieved by the RSM model. The yield of riboflavin was increased to 3.66-fold after 24 h with the optimized parameters. The current research, emphasizes that the Lactobacillus plantarum–HDS27 could be an excellent strain for the large-scale industrial production of riboflavin.

Medium optimization to analyze the protein composition of Bacillus pumilus HR10 antagonizing Sphaeropsis sapinea

A previous study found that a biocontrol bacterium, Bacillus pumilus HR10, inhibited the Sphaeropsis shoot blight disease of pine, and the fermentation broth of HR10 strain contained protein antifungal substances. The optimal formulation of the fermentation medium for the antagonistic substance of B. pumilus HR10 was finally obtained by single-factor test, Packett-Burman test, steepest ascent test and Box-Behnken Design (BBD) response surface test, and the best formulation of the fermentation medium for the antagonistic substance of B. pumilus HR10 was 12 g/L corn meal, 15 g/L beef extract and 13 g/L magnesium sulfate, with a predicted bacterial inhibition rate of 89%. The fermentation filtrate of B. pumilus HR10 cultured with the optimized medium formulation was verified to have an inhibition rate of (87.04 ± 3.2) % on the growth of Sphaeropsis sapinea by three replicate tests. The antagonistic crude protein of B. pumilus HR10 were further isolated and identified using HiTrap Capto Q strong Ion-Exchange Chromatography and LC-MS-MS, and it was speculated that glycoside hydrolase (Ghy), beta-glucanase (Beta), arabinogalactan endonuclease β-1,4-galactanase (Arab), and immunosuppressant A (ImA) are proteins with antagonistic activity against S. sapinea in the B. pumilus HR10.

Using fermentation waste of ethanol-producing yeast for bacterial riboflavin production and recycling of spent bacterial mass for enhancing the growth of oily plants

AIM

This study aims to use fermentation waste of ethanol production (solid and liquid) for riboflavin and recycling of bacterial biomass as biofertilizers to enhance the growth of some oily crop plants.

METHODS AND RESULTS

Out of ten yeast isolates from fresh milk, Clavispora lusitaniae ASU 33 (MN583181) was able to ferment different concentrations of glucose (2.5, 5, 7.5, 10, 15, and 20 %) into ethanol with high efficiency at 10%. Among seven non-Lactobacillus bacterial isolates recovered from cheese samples, two bacterial isolates Bacillus subtlis-SR2 (MT002768) and Novosphingobium panipatense-SR3 (MT002778) were selected for their high riboflavin production. Different media (control medium, fermentation waste medium, and a mixture of the fermentation waste medium and control medium (1:1)) were used for riboflavin production. These media were inoculated by a single or mixture of B. subtlis-SR2, N. panipatense-SR3. The addition of the waste medium of ethanol production to the control medium (1:1) had a stimulatory effect on riboflavin production whether inoculated either with a single strain or mixture of B. subtlis-SR2, N. panipatense-SR3. A mixture of fermentation waste and control media inoculated with N. panipatense produced a high riboflavin yield in comparison with other media. Inoculation of Zea mays and Ocimum basilicum plants either with the bacterial biomass waste of riboflavin production (B. subtlis or N. panipatense or a mixture of B. subtlis and N. panipatense) shows a stimulatory effect on the plant growth in comparison with control (uninoculated plants).

CONCLUSIONS

These results demonstrate the possibility of minimizing the cost of riboflavin and biofertilizer manufacturing via interlinking ethanol and riboflavin with the biofertilizer production technology.

SIGNIFICANCE AND IMPACT OF STUDY

This study outlines methods of evaluating the strength of spent media by applying procedures developed in the vitamins production industries. Furthermore, bacterial biomass waste can act as an environmentally friendly alternative for agrochemicals.

Strategies to Increase the Production of Biosynthetic Riboflavin

Riboflavin is widely regarded as an essential nutrient that is involved in biological oxidation in vivo. In addition to preventing and treating acyl-CoA dehydrogenase deficiency in patients with keratitis, stomatitis, and glossitis, riboflavin is also closely related to the treatment of radiation mucositis and cardiovascular disease. Chemical synthesis has been the dominant method for producing riboflavin for approximately 50 years. Nevertheless, due to the intricate synthesis process, relatively high cost, and high risk of pollution, alternative methods of chemical syntheses, such as the fermentation method, began to develop and eventually became the main methods for producing riboflavin. At present, there are three types of strains used in industrial riboflavin production: Ashbya gossypii, Candida famata, and Bacillus subtilis. Additionally, many recent studies have been conducted on Escherichia coli and Lactobacillus. Fermentation increases the yield of riboflavin using genetic engineering technology to modify and induce riboflavin production in the strain, as well as to regulate the metabolic flux of the purine pathway and pentose phosphate pathway (PP pathway), thereby optimizing the culture process. This article briefly introduces recent progress in the fermentation of riboflavin.

Production of Vitamin B2 (Riboflavin) by Microorganisms: An Overview

Riboflavin is a crucial micronutrient that is a precursor to coenzymes flavin mononucleotide and flavin adenine dinucleotide, and it is required for biochemical reactions in all living cells. For decades, one of the most important applications of riboflavin has been its global use as an animal and human nutritional supplement. Being well-informed of the latest research on riboflavin production via the fermentation process is necessary for the development of new and improved microbial strains using biotechnology and metabolic engineering techniques to increase vitamin B2 yield. In this review, we describe well-known industrial microbial producers, namely, Ashbya gossypii, Bacillus subtilis, and Candida spp. and summarize their biosynthetic pathway optimizations through genetic and metabolic engineering, combined with random chemical mutagenesis and rational medium components to increase riboflavin production.

A novel strain of acetic acid bacteria Gluconobacter oxydans FBFS97 involved in riboflavin production

A novel bacterial strain of acetic acid bacteria capable of producing riboflavin was isolated from the soil sample collected in Wuhan, China. The isolated strain was identified as Gluconobacter oxydans FBFS97 based on several phenotype characteristics, biochemicals tests, and 16S rRNA gene sequence conducted. Furthermore, the complete genome sequencing of the isolated strain has showed that it contains a complete operon for the biosynthesis of riboflavin. In order to obtain the maximum concentration of riboflavin production, Gluconobacter oxydans FBFS97 was optimized in shake flask cultures through response surface methodology employing Plackett–Burman design (PBD), and Central composite design (CCD). The results of the pre-experiments displayed that fructose and tryptone were found to be the most suitable sources of carbon and nitrogen for riboflavin production. Then, PBD was conducted for initial screening of eleven minerals (FeSO₄, FeCl₃, KH₂PO₄, K₂HPO₄, MgSO₄, ZnSO₄, NaCl, CaCl₂, KCl, ZnCl₂, and AlCl₃.6H₂O) for their significances on riboflavin production by Gluconobacter oxydans strain FBFS97. The most significant variables affecting on riboflavin production are K₂HPO₄ and CaCl₂, the interaction affects and levels of these variables were optimized by CCD. After optimization of the medium compositions for riboflavin production were determined as follows: fructose 25 g/L, tryptone 12.5 g/L, K₂HPO₄ 9 g/L, and CaCl₂ 0.06 g/L with maximum riboflavin production 23.24 mg/L.

Enhancement of Aeribacillus pallidus strain VP3 lipase catalytic activity through optimization of medium composition using Box-Behnken design and its application in detergent formulations

Lipases are hydrolytic enzymes owing much importance in industrial applications. These enzyme-based detergents are ecofriendly and produce a wastewater with low level of COD (chemical oxygen demand). In the present work, a novel halophilous, thermoalkaline, and detergent-tolerant lipase produced by a newly isolated Aeribacillus pallidus strain VP3 was studied. Considerable interest has been given to this lipase by the improvement of its catalytic activity through the optimization of the pH, the (C/N) ratio, and the inoculum size, using the response surface methodology based on the Box-Behnken design of experiments. A total of 16 experiments were conducted, and the optimized pH, (C/N) ratio, and inoculum size were 10, 1, and 0.3, respectively. The results of the analysis of variance (ANOVA) test indicated that the established model was significant (p value < 0.05). The optimization of the production conditions leads to 2.83-fold of increase in the catalytic activity calculated as the ratio of the activity obtained after optimization (68 U) and the initial activity before optimization (24 U). All in all, the lipase of Aeribacillus pallidus could be considered as a potential candidate to be incorporated in detergent formulations since it shows a good stability towards detergents and wash performance.

Production of riboflavin and related cofactors by biotechnological processes

Riboflavin (RF) and its active forms, the cofactors flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD), have been extensively used in the food, feed and pharmaceutical industries. Modern commercial production of riboflavin is based on microbial fermentation, but the established genetically engineered production strains are facing new challenges due to safety concerns in the food and feed additives industry. High yields of flavin mononucleotide and flavin adenine dinucleotide have been obtained using whole-cell biocatalysis processes. However, the necessity of adding expensive precursors results in high production costs. Consequently, developing microbial cell factories that are capable of efficiently producing flavin nucleotides at low cost is an increasingly attractive approach. The biotechnological processes for the production of RF and its cognate cofactors are reviewed in this article.

Improvement of stress tolerance and riboflavin production of Bacillus subtilis by introduction of heat shock proteins from thermophilic bacillus strains

In this study, stress tolerance devices consisting of heat shock protein (HSP) genes from thermophiles Geobacillus and Parageobacillus were introduced into riboflavin-producing strain Bacillus subtilis 446 to improve its stress tolerance and riboflavin production. The 12 HSP homologs were selected from 28 Geobacillus and Parageobacillus genomes according to their sequence clustering and phylogenetically analysis which represents the diversity of HSPs from thermophilic bacillus. The 12 HSP genes and 2 combinations of them (PtdnaK-PtdnaJ-PtgrpE and PtgroeL-PtgroeS) were heterologously expressed in B. subtilis 446 under the control of a strong constitutive promoter P43. Most of the 14 engineered strains showed increased cell density at 44 to 48 °C and less cell death at 50 °C compared with the control strains. Among them, strains B.s446-HSP20-3, B.s446-HSP20-2, and B.s446-PtDnaK-PtDnaJ-PtGrpE increased their cell densities over 25% at 44 to 48 °C. They also showed 5-, 4-, and 4-fold improved cell survivals after the 10-h heat shock treatment at 50 °C, respectively. These three strains also showed reduced cell death rates under osmotic stress of 10% NaCl, indicating that the introduction of HSPs improved not only the heat tolerance of B. subtilis 446 but also its osmotic tolerance. Fermentation of these three strains at higher temperatures of 39 and 43 °C showed 23-66% improved riboflavin titers, as well as 24-h shortened fermentation period. These results indicated that implanting HSPs from thermophiles to B. subtilis 446 would be an efficient approach to improve its stress tolerance and riboflavin production.

Design of a high-efficiency synthetic system for l-asparaginase production in Bacillus subtilis

l-asparaginase has high application value in medicine and food industry, but the low yield limits its application. In this study, we designed a synthetic system in Bacillus subtilis to produce l-asparaginase by improving gene expression and optimizing the fermentation agitation speed. Gene expression was improved by respectively increasing transcription levels and translation speeds through screening promoters and RBS sequences. With the optimal promoter, P43, and the synthetic RBS sequence, the yield obtained in a shake flask was 371.87 U/mL, which was 2.09 times that with the original strain. To further enhance production in a 5-L fermenter, a multistage agitation speed control strategy was adopted, involving agitation at 600 rpm for the first 12 h, followed by a gradual increase in speed to 900 rpm, which resulted in the highest yield of l-asparaginase, 5321 U/mL, after 42 h of fermentation.

Mixomics analysis of Bacillus subtilis: effect of oxygen availability on riboflavin production

Background

Riboflavin, an intermediate of primary metabolism, is one kind of important food additive with high economic value. The microbial cell factory Bacillus subtilis has already been proven to possess significant importance for the food industry and have become one of the most widely used riboflavin-producing strains. In the practical fermentation processes, a sharp decrease in riboflavin production is encountered along with a decrease in the dissolved oxygen (DO) tension. Influence of this oxygen availability on riboflavin biosynthesis through carbon central metabolic pathways in B. subtilis is unknown so far. Therefore the unveiled effective metabolic pathways were still an unaccomplished task till present research work.

Results

In this paper, the microscopic regulation mechanisms of B. subtilis grown under different dissolved oxygen tensions were studied by integrating ¹³C metabolic flux analysis, metabolomics and transcriptomics. It was revealed that the glucose metabolic flux through pentose phosphate (PP) pathway was lower as being confirmed by smaller pool sizes of metabolites in PP pathway and lower expression amount of ykgB at transcriptional level. The latter encodes 6-phosphogluconolactonase (6-PGL) under low DO tension. In response to low DO tension in broth, the glucose metabolic flux through Embden–Meyerhof–Parnas (EMP) pathway was higher and the gene, alsS, encoding for acetolactate synthase was significantly activated that may result due to lower ATP concentration and higher NADH/NAD⁺ ratio. Moreover, ResE, a membrane-anchored protein that is capable of oxygen regulated phosphorylase activity, and ResD, a regulatory protein that can be phosphorylated and dephosphorylated by ResE, were considered as DO tension sensor and transcriptional regulator respectively.

Conclusions

This study shows that integration of transcriptomics, ¹³C metabolic flux analysis and metabolomics analysis provides a comprehensive understanding of biosynthesized riboflavin’s regulatory mechanisms in B. subtilis grown under different dissolved oxygen tension conditions. The two-component system, ResD–ResE, was considered as the signal receiver of DO tension and gene regulator that led to differences between biomass and riboflavin production after triggering the shifts in gene expression, metabolic flux distributions and metabolite pool sizes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12934-017-0764-z) contains supplementary material, which is available to authorized users.

In Vitro Evaluation and Statistical Optimization of Antimicrobial Activity of Prunus cerasoides Stem Bark

Nature is a generous source of compounds with the potential for prevention of infections. Antimicrobial screening of aqueous extract from bark of wild Himalayan cherry (Prunus cerasoides) was carried out against various pathogenic microorganisms with inhibition zone ranging from 19 to 24 mm. An optimization strategy, which included classical method and statistical method (RSM), was applied to optimize the effect of process variables. Fifteen percent plant material extracted at 40 °C for 60 min and at its natural pH (4.5) exhibited best antimicrobial activity with an average zone of inhibition ranging from 19 to 29 mm. Statistical optimization using RSM further enhanced the activity by 1.09-1.24 folds. Minimum inhibitory concentration of the aqueous extract against different microorganism ranged from 1 to 10 mg/ml. The aqueous extract was found to be reasonably thermostable at boiling temperature for 1 h. Viable cell count (VCC) studies of the extract showed it to be bactericidal in nature. Further, the aqueous extract was found to be neither cytotoxic nor mutagenic, when evaluated by MTT assay and Ames mutagenicity test. The results suggest that the aqueous extract of P. cerasoides could be a potential source to obtain new antimicrobials and effective herbal medicines to combat the problem of ever emerging microbial resistance.

Significantly enhancing recombinant alkaline amylase production in Bacillus subtilis by integration of a novel mutagenesis-screening strategy with systems-level fermentation optimization

Background

Alkaline amylase has significant potential for applications in the textile, paper and detergent industries, however, low yield of which cannot meet the requirement of industrial application. In this work, a novel ARTP mutagenesis-screening method and fermentation optimization strategies were used to significantly improve the expression level of recombinant alkaline amylase in B. subtilis 168.

Results

The activity of alkaline amylase in mutant B. subtilis 168 mut-16# strain was 1.34-fold greater than that in the wild-type, and the highest specific production rate was improved from 1.31 U/(mg·h) in the wild-type strain to 1.57 U/(mg·h) in the mutant strain. Meanwhile, the growth of B. subtilis was significantly enhanced by ARTP mutagenesis. When the agitation speed was 550 rpm, the highest activity of recombinant alkaline amylase was 1.16- and 1.25-fold of the activities at 450 and 650 rpm, respectively. When the concentration of soluble starch and soy peptone in the initial fermentation medium was doubled, alkaline amylase activity was increased 1.29-fold. Feeding hydrolyzed starch and soy peptone mixture or glucose significantly improved cell growth, but inhibited the alkaline amylase production in B. subtilis 168 mut-16#. The highest alkaline amylase activity by feeding hydrolyzed starch reached 591.4 U/mL, which was 1.51-fold the activity by feeding hydrolyzed starch and soy peptone mixture. Single pulse feeding-based batch feeding at 10 h favored the production of alkaline amylase in B. subtilis 168 mut-16#.

Conclusion

The results indicated that this novel ARTP mutagenesis-screening method could significantly improve the yield of recombinant proteins in B. subtilis. Meanwhile, fermentation optimization strategies efficiently promoted expression of recombinant alkaline amylase in B. subtilis 168 mut-16#. These findings have great potential for facilitating the industrial-scale production of alkaline amylase and other enzymes, using B. subtilis cultures as microbial cell factories.

Statistical experimental designs for the production of secondary metabolites in plant cell suspension cultures

Statistical experimental designs, also known as the "design of experiments" (DoE) approach, are widely used to improve not only technical processes but also to answer questions in the agricultural, medical and social sciences. Although many articles have been published about the application of DoE in these fields, few studies have addressed the use of DoE in the plant sciences, particularly in the context of plant cell suspension cultures (PCSCs). Compounds derived from PCSCs can be developed as pharmaceuticals, chemical feedstocks and cosmetic ingredients, and statistical experimental designs can be used to improve the productivity of the cells and the yield and/or quality of the target compounds in a cost efficient manner. In this article, we summarize recent findings concerning the application of statistical approaches to improve the performance of PCSCs and discuss the potential future applications of this approach.

The effect of temperature and methanol-water mixture on pressurized hot water extraction (PHWE) of anti-HIV analogoues from Bidens pilosa

Background

Pressurized hot water extraction (PHWE) technique has recently gain much attention for the extraction of biologically active compounds from plant tissues for analytical purposes, due to the limited use of organic solvents, its cost-effectiveness, ease-of-use and efficiency. An increase in temperature results in higher yields, however, issues with degradation of some metabolites (e.g. tartrate esters) when PHWE is conditioned at elevated temperatures has greatly limited its use. In this study, we considered possibilities of optimizing PHWE of some specific functional metabolites from Bidens pilosa using solvent compositions of 0, 20, 40 and 60 % methanol and a temperature profile of 50, 100 and 150 °C.

Results

The extracts obtained were analyzed using UPLC-qTOF-MS/MS and the results showed that both temperature and solvent composition were critical for efficient recovery of target metabolites, i.e., dicaffeoylquinic acid (diCQA) and chicoric acid (CA), which are known to possess anti-HIV properties. It was also possible to extract different isomers (possibly cis-geometrical isomers) of these molecules. Significantly differential (p ≤ 0.05) recovery patterns corresponding to the extraction conditions were observed as recovery increased with increase in methanol composition as well as temperature. The major compounds recovered in descending order were 3,5-diCQA with relative peak intensity of 204.23 ± 3.16 extracted at 50 °C and 60 % methanol; chicoric acid (141.00 ± 3.55) at 50 °C and 60 % methanol; 4,5-diCQA (108.05 ± 4.76) at 150 °C and 0 % methanol; 3,4-diCQA (53.04 ± 13.49) at 150 °C and 0 % methanol; chicoric acid isomer (40.01 ± 1.14) at 150 °C and 20 % methanol; and cis-3,5-diCQA (12.07 ± 5.54) at 100 °C and 60 % methanol. Fitting the central composite design response surface model to our data generated models that fit the data well with R² values ranging from 0.57 to 0.87. Accordingly, it was possible to observe on the response surface plots the effects of temperature and solvent composition on the recovery patterns of these metabolites as well as to establish the optimum extraction conditions. Furthermore, the pareto charts revealed that methanol composition had a stronger effect on extraction yield than temperature.

Conclusion

Using methanol as a co-solvent resulted in significantly higher (p ≤ 0.05) even at temperatures as low as 50 °C, thus undermining the limitation of thermal degradation at higher temperatures during PHWE.

Feeding strategy design for recombinant human growth hormone production by Bacillus subtilis

Defined and semi-defined medium-based feeding strategies were developed to enhance recombinant human growth hormone (rhGH) production by Bacillus subtilis BGSC-1A178 (scoC (-)) strain carrying pMK4::pre(subC)::hGH. Defined medium-based feeding strategies were designed by exponential feeding of glucose and (NH4)2HPO4 at two pre-determined specific growth rates, µ 0 = 0.10 and 0.17 h(-1). Semi-defined medium-based feeding strategies were designed by exponential feeding of substrate solution consisting of glucose, (NH4)2HPO4, peptone, and trace salt solution (PTM1) at three pre-determined specific growth rates, µ 0 = 0.10, 0.17, and 0.25 h(-1). At all the strategies applied, transition cultivation time from batch to fed-batch operation was t T = 4 h. The highest rhGH concentration was obtained as C rhGH = 0.5 g L(-1) with semi-defined medium-based feeding strategy designed with µ 0 = 0.25 h(-1) using feed substrate stock solution containing 200 g L(-1) glucose, 117 g L(-1) (NH4)2HPO4, 100 g L(-1) peptone, and 5 mL L(-1) PTM1 at t = 22 h when the cell concentration reached to C X = 8.29 g L(-1). The overall product and cell yields on glucose were obtained as [Formula: see text] = 7.21 mg g(-1) and [Formula: see text] = 0.12 g g(-1), respectively. The results indicate the requirement of designing continuous feed stream in fed-batch production to enhance rhGH production by r-B. subtilis.

A versatile coupled cell-free transcription-translation system based on tobacco BY-2 cell lysates

Cell-free protein synthesis is a powerful method for the high-throughput production of recombinant proteins, especially proteins that are difficult to express in living cells. Here we describe a coupled cell-free transcription-translation system based on tobacco BY-2 cell lysates (BYLs). Using a combination of fractional factorial designs and response surface models, we developed a cap-independent system that produces more than 250 μg/mL of functional enhanced yellow fluorescent protein (eYFP) and about 270 μg/mL of firefly luciferase using plasmid templates, and up to 180 μg/mL eYFP using linear templates (PCR products) in 18 h batch reactions. The BYL contains actively-translocating microsomal vesicles derived from the endoplasmic reticulum, promoting the formation of disulfide bonds, glycosylation and the cotranslational integration of membrane proteins. This was demonstrated by expressing a functional full-size antibody (∼ 150 μg/mL), the model enzyme glucose oxidase (GOx) (∼ 7.3 U/mL), and a transmembrane growth factor (∼ 25 μg/mL). Subsequent in vitro treatment of GOx with peptide-N-glycosidase F confirmed the presence of N-glycans. Our results show that the BYL can be used as a high-throughput expression and screening platform that is particularly suitable for complex and cytotoxic proteins.

Multiparameter optimization method and enhanced production of secreted recombinant single-chain variable fragment against the HIV-1 P17 protein from Escherichia coli by fed-batch fermentation

The single-chain fragment variable (scFv) was used to produce a completely functional antigen-binding fragment in bacterial systems. The advancements in antibody engineering have simplified the method of producing Fv fragments and made it more efficient and generally relevant. In a previous study, the scFv anti HIV-1 P17 protein was produced by a batch production system, optimized by the sequential simplex optimization method. This study continued that work in order to enhance secreted scFv production by fed-batch cultivation, which supported high volumetric productivity and provided a large amount of scFvs for diagnostic and therapeutic research. The developments in cell culture media and process parameter settings were required to realize the maximum production of cells. This study investigated the combined optimization methods, Plackett-Burman design (PBD) and sequential simplex optimization, with the aim of optimize feed medium. Fed-batch cultivation with an optimal feeding rate was determined. The result demonstrated that a 20-mL/hr feeding rate of the optimized medium can increase cell growth, total protein production, and scFv anti-p17 activity by 4.43, 1.48, and 6.5 times more than batch cultivation, respectively. The combined optimization method demonstrated novel power tools for the optimization strategy of multiparameter experiments.

Metabolic and bioprocess engineering of the yeast Candida famata for FAD production

Flavins in the form of flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) play an important role in metabolism as cofactors for oxidoreductases and other enzymes. Flavin nucleotides have applications in the food industry and medicine; FAD supplements have been efficiently used for treatment of some inheritable diseases. FAD is produced biotechnologically; however, this compound is much more expensive than riboflavin. Flavinogenic yeast Candida famata synthesizes FAD from FMN and ATP in the reaction catalyzed by FAD synthetase, a product of the FAD1 gene. Expression of FAD1 from the strong constitutive promoter TEF1 resulted in 7- to 15-fold increase in FAD synthetase activity, FAD overproduction, and secretion to the culture medium. The effectiveness of FAD production under different growth conditions by one of these recombinant strains, C. famata T-FD-FM 27, was evaluated. First, the two-level Plackett-Burman design was performed to screen medium components that significantly influence FAD production. Second, central composite design was adopted to investigate the optimum value of the selected factors for achieving maximum FAD yield. FAD production varied most significantly in response to concentrations of adenine, KH2PO4, glycine, and (NH4)2SO4. Implementation of these optimization strategies resulted in 65-fold increase in FAD production when compared to the non-optimized control conditions. Recombinant strain that has been cultivated for 40 h under optimized conditions achieved a FAD accumulation of 451 mg/l. So, for the first time yeast strains overproducing FAD were obtained, and the growth media composition for maximum production of this nucleotide was designed.

Construction and fed-batch cultivation of Candida famata with enhanced riboflavin production

Riboflavin (vitamin B2) is an essential nutrition component serving as a precursor of coenzymes FMN and FAD that are involved mostly in reactions of oxidative metabolism. Riboflavin is produced in commercial scale and is used in feed and food industries, and in medicine. The yeast Candida famata (Candida flareri) belongs to the group of so called "flavinogenic yeasts" which overproduce riboflavin under iron limitation. Three genes SEF1, RIB1 and RIB7 coding for a putative transcription factor, GTP cyclohydrolase II and riboflavin synthase, respectively were simultaneously overexpressed in the background of a non-reverting riboflavin producing mutant AF-4, obtained earlier in our laboratory using methods of classical selection (Dmytruk et al. (2011), Metabolic Engineering 13, 82-88). Cultivation conditions of the constructed strain were optimized for shake-flasks and bioreactor cultivations. The constructed strain accumulated up to 16.4g/L of riboflavin in optimized medium in a 7L laboratory bioreactor during fed-batch fermentation.

Enhanced riboflavin production by recombinant Bacillus subtilis RF1 through the optimization of agitation speed

Dissolved oxygen is one of the most important bioprocess parameters that could affect cell growth and product formation, and it is easy to control by changing agitation speed. In this work, the effects of agitation speed on the performance of riboflavin production by recombinant Bacillus subtilis RF1 was investigated in fed-batch fermentation. The lower agitation speed (600 rpm) was beneficial for cell growth and riboflavin biosynthesis in the initial phase of fermentation process. While, during the later phase, higher agitation speed (900 rpm) was favor for cell growth and riboflavin biosynthesis. Thus, a two-stage agitation speed control strategy was proposed based on kinetic analysis, in which the agitation speed was controlled at 600 rpm in the first 26 h and then switched to 900 rpm to maintain high μ for cell growth and high q(p) for riboflavin production during the entire fermentation process. However, it was observed that a sharp increase of agitation speed resulted in an adverse effect on cell growth and riboflavin synthesis within a short time. To avoid this phenomenon, a multi-stage agitation speed control strategy was set up based on the two-stage control strategy, the maximum concentration of riboflavin reached 9.4 g l(-1) in 48 h with the yield of 0.051 g g(-1) by applying this strategy, which were 20.5 and 21.4% over the best results controlled by constant agitation speeds.

Optimization of BY-2 cell suspension culture medium for the production of a human antibody using a combination of fractional factorial designs and the response surface method

We have developed a strategy for the optimization of plant cell suspension culture media using a combination of fractional factorial designs (FFDs) and response surface methodology (RSM). This sequential approach was applied to transformed tobacco BY-2 cells secreting a human antibody (M12) into the culture medium, in an effort to maximize yields. We found that the nutrients KNO₃, NH₄NO₃ and CaCl₂ and the hormones 2,4-dichlorophenoxyacetic acid (2,4-D) and 6-benzylaminopurine (BAP) had the most significant impact on antibody accumulation. The factorial screening revealed strong interactions within the nutrients group (KNO₃, NH₄NO₃ and CaCl₂) and also individually between 2,4-D and three other components (KNO₃, NH₄NO₃ and BAP). The RSM design resulted in a fivefold increase in the antibody concentration after 5 days and a twofold reduction in the packed cell volume (PCV). Longer cultivation in the optimized medium led to the further accumulation of antibody M12 in the culture medium (up to 107 μg/mL, day 10). Because the packed cell volume was reduced in the optimized medium, this enhanced the overall yield by 20-fold (day 7) and 31-fold (day 10) compared to the conventional MS medium.

Optimization of Antioxidant Potential of Penicillium granulatum Bainier by Statistical Approaches

A three-step optimization strategy which includes one-factor-at-a-time classical method and different statistical approaches (Plackett-Burman design and response surface methodology) that were applied to optimize the antioxidant potential of Penicillium granulatum. Antioxidant activity was assayed by different procedures and compared with total phenolic content. Primarily, different carbon and nitrogen sources were screened by classical methods, which revealed sucrose and NaNO3 to be the most suitable. In second step, Plackett-Burman design also supported sucrose and NaNO3 to be the most significant. In third step, response surface analysis showed 4.5% sucrose, 0.1% NaNO3, and incubation temperature of 25°C to be the optimal conditions. Under these conditions, the antioxidant potential assayed through different procedures was 78.2%, 70.1%, and 78.9% scavenging effect for DPPH radical, ferrous ion, and nitric oxide ion, respectively. The reducing power showed an absorbance of 1.6 with 68.5% activity for FRAP assay.

MODELING AND ANALYZING THE METABOLISM OF RIBOFLAVIN PRODUCTION USING PETRI NETS

A number of recent studies have focused on structural and functional analysis and simulation of biochemical pathways, and it suggested that these structure-oriented analysis methods could be greatly helpful for the understanding of the metabolism. Among several structural analysis methods, Petri nets analysis (PNA) has a visual representation that facilitates users' comprehension and thus is employed in this study. The main results in the present paper are: (1) an in silico model of the metabolism of riboflavin production in bacillus subtilis based on PNA; and (2) a study with structural analysis. The obtained invariants are analyzed and classified based on their structural and functional capabilities.

B-group vitamin production by lactic acid bacteria--current knowledge and potential applications

Although most vitamins are present in a variety of foods, human vitamin deficiencies still occur in many countries, mainly because of malnutrition not only as a result of insufficient food intake but also because of unbalanced diets. Even though most lactic acid bacteria (LAB) are auxotrophic for several vitamins, it is now known that certain strains have the capability to synthesize water-soluble vitamins such as those included in the B-group (folates, riboflavin and vitamin B(12) amongst others). This review article will show the current knowledge of vitamin biosynthesis by LAB and show how the proper selection of starter cultures and probiotic strains could be useful in preventing clinical and subclinical vitamin deficiencies. Here, several examples will be presented where vitamin-producing LAB led to the elaboration of novel fermented foods with increased and bioavailable vitamins. In addition, the use of genetic engineering strategies to increase vitamin production or to create novel vitamin-producing strains will also be discussed. This review will show that the use of vitamin-producing LAB could be a cost-effective alternative to current vitamin fortification programmes and be useful in the elaboration of novel vitamin-enriched products.

Medium composition influence on Biotin and Riboflavin production by newly isolated Candida sp

Complex B vitamins as Biotin and Riboflavin are required by living organisms, not only for growth but also for metabolite production, and the feed market classifies them as growth promoters. Since Brazil will soon be one of the world's biggest animal protein producers, feed production is a large consumer of vitamins and micronutrients. The industry requires 10 mg riboflavin/0.2 mg biotin per kilogram of feed; a ratio of 40 ~ 50:1. Although few studies have been conducted specifically on riboflavin production using factorial design and surface response method as an optimization strategy, it is a common practice in biotechnology with many research reports available. However, there are no reports on the use of statistical design for biotin production. This study set out to evaluate medium composition influence on biotin and riboflavin production using a statistical design. There are no studies relating biotin and riboflavin production by Candida sp LEB 130. In this preliminary study to improve the simultaneous production of biotin and riboflavin, the maximum riboflavin/biotin ratio of 8.3 μg/mL was achieved with medium component concentrations of: sucrose 30 g/L, KH2PO4 2 g/L, MgSO4 1 g/L and ZnSO4 0.5mL/L.

Genetic control of biosynthesis and transport of riboflavin and flavin nucleotides and construction of robust biotechnological producers

Riboflavin [7,8-dimethyl-10-(1'-d-ribityl)isoalloxazine, vitamin B₂] is an obligatory component of human and animal diets, as it serves as the precursor of flavin coenzymes, flavin mononucleotide, and flavin adenine dinucleotide, which are involved in oxidative metabolism and other processes. Commercially produced riboflavin is used in agriculture, medicine, and the food industry. Riboflavin synthesis starts from GTP and ribulose-5-phosphate and proceeds through pyrimidine and pteridine intermediates. Flavin nucleotides are synthesized in two consecutive reactions from riboflavin. Some microorganisms and all animal cells are capable of riboflavin uptake, whereas many microorganisms have distinct systems for riboflavin excretion to the medium. Regulation of riboflavin synthesis in bacteria occurs by repression at the transcriptional level by flavin mononucleotide, which binds to nascent noncoding mRNA and blocks further transcription (named the riboswitch). In flavinogenic molds, riboflavin overproduction starts at the stationary phase and is accompanied by derepression of enzymes involved in riboflavin synthesis, sporulation, and mycelial lysis. In flavinogenic yeasts, transcriptional repression of riboflavin synthesis is exerted by iron ions and not by flavins. The putative transcription factor encoded by SEF1 is somehow involved in this regulation. Most commercial riboflavin is currently produced or was produced earlier by microbial synthesis using special selected strains of Bacillus subtilis, Ashbya gossypii, and Candida famata. Whereas earlier RF overproducers were isolated by classical selection, current producers of riboflavin and flavin nucleotides have been developed using modern approaches of metabolic engineering that involve overexpression of structural and regulatory genes of the RF biosynthetic pathway as well as genes involved in the overproduction of the purine precursor of riboflavin, GTP.

Metabolic engineering and classic selection of the yeast Candida famata (Candida flareri) for construction of strains with enhanced riboflavin production

Currently, the mutant of the flavinogenic yeast Candida famata dep8 isolated by classic mutagenesis and selection is used for industrial riboflavin production. Here we report on construction of a riboflavin overproducing strain of C. famata using a combination of random mutagenesis based on the selection of mutants resistant to different antimetabolites as well as rational approaches of metabolic engineering. The conventional mutagenesis involved consecutive selection for resistance to riboflavin structural analog 7-methyl-8-trifluoromethyl-10-(1'-d-ribityl)isoalloxazine), 8-azaguanine, 6-azauracil, 2-diazo-5-oxo-L-norleucine and guanosine as well as screening for yellow colonies at high pH. The metabolic engineering approaches involved introduction of additional copies of transcription factor SEF1 and IMH3 (coding for IMP dehydrogenase) orthologs from Debaryomyces hansenii, and the homologous genes RIB1 and RIB7, encoding GTP cyclohydrolase II and riboflavin synthetase, the first and the last enzymes of riboflavin biosynthesis pathway, respectively. Overexpression of the aforementioned genes in riboflavin overproducer AF-4 obtained by classical selection resulted in a 4.1-fold increase in riboflavin production in shake-flask experiments. D. hansenii IMH3 and modified ARO4 genes conferring resistance to mycophenolic acid and fluorophenylalanine, respectively, were successfully used as new dominant selection markers for C. famata.

Medium optimization for the feather-degradation by Streptomyces fradiae Var S-221 using the response surface methodology

In order to accelerate biodegradation of feather into more amino acids, the fermentation medium of feather-biodegrading Streptomyces fradiae Var S-221 was optimized in this paper. In the first optimization step, the effects of feather powder, beet molasses, (NH(4))(2)SO(4) and KH(2)PO(4) on amino acids formation were evaluated by using full factorial design. The results showed that feather powder and (NH(4))(2)SO(4) had significant and positive effects on feather-biodegradation into amino acids. Then, the method of the steepest ascent was used to access the optimal region of the two significant factors. In the third step, the concentration of feather powder and (NH(4))(2)SO(4) were further optimized with central composite design and response surface analysis. As a result, the composition of the optimal medium for S. fradiae Var S-221 fermentation were as follows (g/100 ml): feather powder, 19.504; beet molasses, 4.0; (NH(4))(2)SO(4), 1.467; KH(2)PO(4), 0.3; MgSO(4), 0.15; FeSO(4), 0.001; ZnSO(4), 0.0001; and MnSO(4), 0.0001. Using this optimal fermentation medium, the amino acids concentration was increased from 4.61 to 6.13 g/100 ml.