Composition Of Fermentation Medium Research Articles

Enhancing the yield of Xenocoumacin 1 in Xenorhabdus nematophila YL001 by optimizing the fermentation process

Xenocoumacin 1 (Xcn 1), antibiotic discovered from secondary metabolites of Xenorhabdus nematophila, had the potential to develop into a new pesticide due to its excellent activity against bacteria, oomycetes and fungi. However, the current low yield of Xcn1 limits its development and utilization. To improve the yield of Xcn1, response surface methodology was used to determine the optimal composition of fermentation medium and one factor at a time approach was utilized to optimize the fermentation process. The optimal medium composed of in g/L: proteose peptone 20.8; maltose 12.74; K2HPO4 3.77. The optimal fermentation conditions were that 25 °C, initial pH 7.0, inoculum size 10%, culture medium 75 mL in a 250 mL shake flask with an agitation rate of 150 rpm for 48 h. Xenorhabdus nematophila YL001 was produced the highest Xcn1 yield (173.99 mg/L) when arginine was added to the broth with 3 mmol/L at the 12th h. Compared with Tryptic Soy Broth medium, the optimized fermentation process resulted in a 243.38% increase in Xcn1 production. The obtained results confirmed that optimizing fermentation technology led to an increase in Xcn1 yield. This work would be helpful for efficient Xcn1 production and lay a foundation for its industrial production.

Antibacterial Komagataeibacter hansenii nanocellulose membranes with avocado seed bioactive compounds

AbstractBiocompatible, mechanically stable, highly hydrophilic/swellable and safe antibacterial biomaterials are crucial for wound dressing and other applications in the health sector. Therefore, this study was conducted for the development of bacterial nanocellulose membranes, which were, for the first time, enriched with bacteriostatic and bactericidal effective avocado seed extracts prepared by different extraction techniques (ultrasonic, Soxhlet, high pressure with supercritical carbon dioxide). First, the production process of bacterial nanocellulose membranes from Komagataeibacter hansenii bacteria was optimized related to the fermentation media composition and culture conditions, resulting in bacterial nanocellulose membranes with up to 83% crystallinity and 54.5 g/L yield. The morphological structure of the membranes was varied further by using air- and freeze-drying processes. The Soxhlet and high pressure with supercritical carbon dioxide avocado seed extracts with the most charge negative surface (-33 mV) and smallest hydrodynamic size (0.1 µm) thus resulted in 100% reduction of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus with up to log reduction of 2.56 and up to 100% bactericidal efficacy after 24 h of exposure, and at 14 mg/g of avocado seed extracts integrated in the bacterial nanocellulose membranes homogeneously. The high swelling (up to 600%) and water retention ability of avocado seed extracts enriched bacterial nanocellulose membranes, with a biocidal release up to 2.71 mg/mL, shows potential for antibacterial applications in the biomedicine, cosmetics, and pharmaceutical industries.

State of the Art Technologies for High Yield Heterologous Expression and Production of Oxidoreductase Enzymes: Glucose Oxidase, Cellobiose Dehydrogenase, Horseradish Peroxidase, and Laccases in Yeasts P. pastoris and S. cerevisiae

Oxidoreductase (OXR) enzymes are in high demand for biocatalytic applications in the food industry and cosmetics (glucose oxidase (GOx) and cellobiose dehydrogenase (CDH)), bioremediations (horseradish peroxidase (HRP) and laccase (LAC)), and medicine for biosensors and miniature biofuel cells (GOx, CDH, LAC, and HRP). They can be used in a soluble form and/or within the yeast cell walls expressed as chimeras on the surface of yeast cells (YSD), such as P. pastoris and S. cerevisiae. However, most of the current studies suffer from either low yield for soluble enzyme expression or low enzyme activity when expressed as chimeric proteins using YSD. This is always the case in studies dealing with the heterologous expression of oxidoreductase enzymes, since there is a requirement not only for multiple OXR gene integrations into the yeast genome (super transformations), and codon optimization, but also very careful design of fermentation media composition and fermentation conditions during expression due to the need for transition metals (copper and iron) and metabolic precursors of FAD and heme. Therefore, scientists are still trying to find the optimal formula using the above-mentioned approaches; most recently, researcher started using protein engineering and directed evolution to increase in the yield of recombinant enzyme production. In this review article, we will cover all the current state-of-the-art technologies and most recent advances in the field that yielded a high expression level for some of these enzymes in specially designed expression/fermentation systems. We will also tackle and discuss new possibilities for further increases in fermentation yield using cutting-edge technologies such as directed evolution, protein and strain engineering, high-throughput screening methods based on in vitro compartmentalization, flow cytometry, and microfluidics.

Sustainable bio-manufacturing of D-arabitol through combinatorial engineering of Zygosaccharomyces rouxii, bioprocess optimization and downstream separation

Biosynthesis of D-arabitol, a high value-added platform chemical, from renewable carbon sources provides a sustainable and eco-friendly alternative to the chemical industry. Here, a robust brewing yeast, Zygosaccharomyces rouxii, capable of naturally producing D-arabitol was rewired through genome sequencing-based metabolic engineering. The recombinant Z. rouxii obtained by reinforcing the native D-xylulose pathway, improving reductive power of the rate-limiting step, and inhibiting the shunt pathway, produced 73.61% higher D-arabitol than the parent strain. Subsequently, optimization of the fermentation medium composition for the engineered strain provided 137.36 g/L D-arabitol, with a productivity of 0.64 g/L/h in a fed-batch experiment. Finally, the downstream separation of D-arabitol from the complex fermentation broth using an ethanol precipitation method provided a purity of 96.53%. This study highlights the importance of D-xylulose pathway modification in D-arabitol biosynthesis, and pave a complete and efficient way for the sustainable manufacturing of this value-added compound from biosynthesis to preparation.

Enhanced expression of a novel trypsin from Streptomyces fradiae in Komagataella phaffii GS115 through combinational strategies of propeptide engineering and self-degredation sites modification

This study aimed to enhance the expression level of a novel trypsin gene from Streptomyces fradiae ATCC14544 in Komagataella phaffii GS115 through the combinational use of propeptide engineering and self-degradation residues modification strategies. An artificial propeptide consisted of thioredoxin TrxA, the bovine propeptide DDDDK and the hydrophobic peptide FVEF was introduced to replace the original propeptide while the self-degradation residue sites were predicted and analyzed through alanine screening. The results showed that the quantity and enzymatic activity of asft with engineered propeptide reached 47.02 mg/mL and 33.9 U/mL, which were 9.6 % and 59.29 % higher than those of wild-type (42.9 mg/mL and 13.8 U/mL). Moreover, the introduction of R295A/R315A mutation further enhanced the enzymatic activity (58.86 U/mL) and obviously alleviated the phenomena of self-degradation. The tolerance of trypsin towards alkaline environment was also improved since the optimal pH was shifted from pH 9.0 to pH 9.5 and the half-life value at pH 10 was significantly extended. Finally, the fermentation media composition and condition were optimized and trypsin activity in optimal condition reached 160.58 U/mL, which was 2.73-fold and 11.64-fold of that before optimization or before engineering. The results obtained in this study indicated that the combinational use of propeptide engineering and self-degradation sites modification might have great potential application in production of active trypsins.

Rewiring Bacillus subtilis and bioprocess optimization for oxidoreductive reaction-mediated biosynthesis of D-tagatose

D-tagatose holds significant importance as a functional monosaccharide with diverse applications in food, medicine, and other fields. This study aimed to explore the oxidoreductive pathway for D-tagatose production, surpassing the contemporary isomerization-mediated biosynthesis approach in order to enhance the thermodynamic equilibrium of the reactions. Initially, a novel galactitol dehydrogenase was discovered through biochemical and bioinformatics analyses. By co-expressing the galactitol dehydrogenase and xylose reductase, the oxidoreductive pathway for D-tagatose synthesis was successfully established in Bacillus subtilis. Subsequently, pathway fine-tuning was achieved via promoter regulation and dehydrogenase-mediated cofactor regeneration, resulting in 6.75-fold higher D-tagatose compared to that produced by the strain containing the unmodified promoter. Finally, optimization of fermentation conditions and medium composition produced 39.57 g/L D-tagatose in a fed-batch experiment, with a productivity of 0.33 g/L/h and a yield of 0.55 mol/mol D-galactose. These findings highlight the potential of the constructed redox pathway as an effective approach for D-tagatose production.

A comprehensive screening platform of wood-derived sugars for sophorolipid production: Predictive modelling, sterilization methods and analysis of feedstock composition

Sophorolipid production using conventional food-grade feedstocks such as glucose and rapeseed oil can have detrimental impacts on food supply and commodity prices. The increasing complexity of alternative feeds necessitates efficient management of nutritional (substrate and inhibitor content) and physical (viscosity, particulates) characteristics. To address this, a screening platform was applied that uses predictive modelling to customize the fermentation media composition based on feed substrate content, while employing different preparation methods such as tangential flow filtration or autoclaving to mitigate particulate loading and prevent the formation of inhibitory by-products. To validate the platform, three lignocellulosic sugars (Fibenol OÜ) were tested, including the glucose-rich (C6), xylose-rich (C5), and mixed (C5/C6) sugars. Under the tailored media conditions, the C6 wood-sugar produced 47.12 g/L and 44.33 g/L average sophorolipid with tangential flow filtration and autoclave sterilization, respectively. The C5/C6 wood-sugar only produced sophorolipid with tangential flow filtration (40.15 g/L) whilst the C5 wood-sugar did not produce sophorolipids with either sterilization method. Comparatively, autoclaved glucose produced 33.06 g/L average sophorolipid under conditions matching the C6 and C5 wood-sugars. The combination of predictive profiling and preparation method comparisons allows for effective screening of potentially productive fermentation feeds, with the application of tangential flow filtration for feeds being reported for the first time.

Construction of an efficient Claviceps paspali cell factory for lysergic acid production.

Lysergic acid (LA) is the key precursor of ergot alkaloids, and its derivatives have been used extensively for the treatment of neurological disorders. However, the poor fermentation efficiency limited its industrial application. At the same time, the hardship of genetic manipulation has hindered the metabolic engineering of Claviceps strains to improve the LA titer further. In this study, an efficient genetic manipulation system based on the protoplast-mediated transformation was established in the industrial strain Claviceps paspali. On this basis, the gene lpsB located in the ergot alkaloids biosynthetic gene cluster was deleted to construct the LA-producing cell factory. Plackett-Burman and Box-Behnken designs were used in shaking flasks, achieving an optimal fermentation medium composition. The final titer of LA and iso-lysergic acid (ILA) reached 3.7g·L-1, which was 4.6times higher than that in the initial medium. Our work provides an efficient strategy for the biosynthesis of LA and ILA and lays the groundwork for its industrial production.

Efficient biosynthesis of exopolysaccharide in Candida glabrata by a fed-batch culture.

Polysaccharides are important natural biomacromolecules. In particular, microbial exopolysaccharides have received much attention. They are produced by a variety of microorganisms, and they are widely used in the food, pharmaceutical, and chemical industries. The Candida glabrata mutant 4-C10, which has the capacity to produce exopolysaccharide, was previously obtained by random mutagenesis. In this study we aimed to further enhance exopolysaccharide production by systemic fermentation optimization. By single factor optimization and orthogonal design optimization in shaking flasks, an optimal fermentation medium composition was obtained. By optimizing agitation speed, aeration rate, and fed-batch fermentation mode, 118.6 g L−1 of exopolysaccharide was obtained by a constant rate feeding fermentation mode, with a glucose yield of 0.62 g g−1 and a productivity of 1.24 g L−1 h−1. Scaling up the established fermentation mode to a 15-L fermenter led to an exopolysaccharide yield of 113.8 g L−1, with a glucose yield of 0.60 g g−1 and a productivity of 1.29 g L−1 h−1.

Fermentation optimization, purification and biochemical characterization of a porphyran degrading enzyme with funoran side-activity from Zobellia uliginosa

A porphyran degrading enzyme was obtained from the marine bacterial strain Zobellia uliginosa with a secondary funoran degradation activity. The optimal fermentation conditions were determined using one-factor-at-a-time experiments and the bacteria produced highest amount of enzyme after 72 h of incubation at 25 °C. The optimal fermentation medium composition was identified as 3% sea salt, furcellaran as carbon source, and peptone served as both nitrogen and carbon source. The extracellular enzyme was purified using ultrafiltration, ammonium sulfate precipitation, ion-exchange chromatography and High performance size-exclusion chromatography (HP-SEC). As compared to that in the crude form, the enzyme had a 7751-fold and 5736-fold increase in maximum specific activity resulting in 2.29 U/mg and 1.13 U/mg for porphyran and funoran respectively. Based on the high performance size-exclusion chromatography, the molecular weight of the purified enzyme was estimated at around ∼41 kDa. The enzymatic activity was observed against funoran with a maximum value at 40 °C and pH 7.5; it remained fairly stable until 40 °C. Significant activation was observed with the presence of Fe3+ and Mg2+; whereas, the enzyme activity was majorly inhibited by EDTA and NH4+. This study is the first to present evidence of funoran degrading enzymes from marine bacteria.

Enhanced Biosynthesis of D-Arabitol by Metschnikowia reukaufii Through Optimizing Medium Composition and Fermentation Conditions.

D-Arabitol is an important functional sugar alcohol, which can be used in the preparation of foods, chemicals, and medicines. Despite biological production of D-arabitol from low-cost substrates has recently been the focus of research, low yield of this technology has limited its large-scale exploitation. Optimization of this bioprocess could be a promising option to improve the yield of D-arabitol. In this study, one-factor-at-a-time (OFAT) strategy and Box-Behnken design (BBD) were used to increase D-arabitol production by Metschnikowia reukaufii CICC 31,858 through optimizing the fermentation conditions and medium composition. The OFAT optimization provided the optimal conditions for temperature, agitation speed, and fermentation time of 30℃, 220rpm, and 6days, respectively. Likewise, the optimum concentrations of peptone, ammonium sulfate, KH2PO4, MgSO4·7H2O, and fumaric acid in the fermentation medium were (g/L) 7.5, 1, 2, 0.5, and 7.5, respectively. Under these optimum conditions, 80.43g/L of D-arabitol was produced from 200g/L of glucose, with a productivity of 0.56g/L/h. The BBD optimization with three important components of fermentation medium (KH2PO4, MgSO4·7H2O, and fumaric acid) showed that the predicted titer of D-arabitol varied from 47.21 to 89.27g/L, and the actual titer of D-arabitol ranged from 47.36 to 89.83g/L. The optimum concentrations (g/L) of KH2PO4, MgSO4·7H2O, and fumaric acid in the fermentation medium were found to be 1.0, 0.5, and 4.7g/L, respectively. Under the optimum conditions, 92.45g/L of D-arabitol was finally produced with the yield and productivity of 0.46g/g and 0.64g/L/h, respectively.

Avilamycin production enhancement by mutagenesis and fermentation optimization in Streptomyces viridochromogenes.

Avilamycin, an excellent growth-promoting feed additive, produced by Streptomyces viridochromogenes, was widely used to promote the growth of poultry by inhibiting Gram-positive bacteria. In this work, the methods of combinational mutagenesis of UV (Ultraviolet) and ARTP (Atmospheric and room temperature plasma), and rational screening by high concentrations of CaCl2 were utilized to promote the production of avilamycin. The avilamycin high-yielding mutant strains of Z-6 (29.31mg/L), A-9 (36.84mg/L) and F-23 (45.73mg/L) were screened out, with yields of avilamycin improved by 57.92%, 98.49% and 146.39%, respectively, compared with the wild strain (WT). The performance comparison showed that Z-6, A-9 and F-23 mutant strains had stronger abilities of substrate consumption, cell growth and antibiotic synthesis than WT. Furthermore, the composition of fermentation medium, inoculation parameters, supplementation strategies of oxygen vectors, glucose and precursors (L-valine, D-xylose and sodium acetate) had been optimized and the avilamycin yield of the mutant strain F-23 was significantly enhanced by 41.87% by fermentation optimization. In summary, the strategy of increasing the production of avilamycin in S. viridochromogenes in this work might provide an alternative method to enhance the synthesis of secondary metabolites in other Streptomyces.

Optimization of Yeast Cultivation Factors for Improved SCP Production

Abstract Yeast Single-Cell Proteins (SCP) production using various agro-industrial byproducts and wastes have significant potential as an alternative to the soy meal, and fish meal protein used for livestock and aquaculture feeds. The use of organic wastes as a substrate in the fermentation processes can be accepted as one of the solutions to reduce the total price of the culture and an environmentally friendlier method of removing these residues. This review article focuses on the yeast biomass yield and protein content increase strategies, which is impossible without understanding metabolic pathways and switching mechanisms. The present work discusses optimization strategies for protein-enriched yeast biomass production, such as fermentation medium composition, including a selection of carbon and nitrogen sources and their ratio, supplemented trace elements, and cultivation conditions such as pH, temperature, time of cultivation, and inoculum size. This review summarizes the theoretical knowledge and experimental results of other researchers that provide an overview of the achievements of the last decades in the production of SCP.

Optimization of fermentation medium for succinic acid production using Basfia succiniciproducens

The development of cost-competitive bioprocesses is dependent on the formulation of low cost and efficient fermentation medium. Thus, optimization of nutrient composition in fermentation media combining efficient metabolic product formation with cost-competitiveness is needed. Within this context, the main novelty of this study was to optimize the nutrient composition of a fermentation medium used for bio-based succinic acid production by the wild-type bacterial strain Basfia succiniciproducens JF4016 combining low cost with high succinic acid production efficiency. Two Plackett–Burman​ Designs, a central composite design and constraint optimization were sequentially implemented to estimate the optimum and cost-competitive fermentation medium composition. The two Plackett–Burman Designs identified NaH 2 PO 4 , Na 2 HPO 4 and NaCl as the most important medium components. Central composite design identified the optimum concentrations of NaH 2 PO 4 , Na 2 HPO 4 , NaCl, yeast extract and corn steep liquor leading to the highest productivity. Constraint optimization was employed to maximize productivity using constraints on the final succinic acid concentration, yield, by-products to succinic acid ratio and fermentation medium cost. Validation of the model predictions was carried out in a bioreactor culture at ca. 30 g/L initial glucose concentration. The optimum fermentation medium containing 19.4 g/L CSL, 9.2 g/L yeast extract, 3 g/L NaCl and 4.32 g/L sodium phosphates led to the production of 19 g/L succinic acid concentration, 0.62 g/g yield and 1.9 g/(L ⋅ h) productivity. • Experimental design to optimize fermentation medium for succinic acid production by Basfia succiniciproducens . • Succinic acid production reached 19 g/L with 0.62 g/g yield and 1.9 g/(L⋅h) productivity. • Reduced fermentation medium cost ($1.22/kg SA ) was estimated at the optimal medium composition.

Improvement of tacrolimus production in Streptomyces tsukubaensis by mutagenesis and optimization of fermentation medium using Plackett-Burman design combined with response surface methodology.

This study was conducted to enhance the production of tacrolimus in Streptomyces tsukubaensis by strain mutagenesis and optimization of the fermentation medium. A high tacrolimus producing strain S. tsukubaensis FIM-16-06 was obtained by ultraviolet mutagenesis coupled with atmospheric and room temperature plasma mutagenesis.Then, nine variables were screened using Plackett-Burman experimental design, in which soluble starch, peptone and Tween 80 showed significantly affected tacrolimus production. Further studies were carried out employing central composite design to elucidate the mutual interaction between the variables and to work out optimal fermentation medium composition for tacrolimus production. The optimum fermentation medium was found to contain 61.61g/L of soluble starch, 20.61g/L of peptone and 30.79g/L of Tween 80. In the optimized medium, the production of tacrolimus reached 1293mg/L in shake-flask culture, and reached 1522mg/L while the scaled-up fermentation was conducted in a 1000 L fermenter, which was about 3.7 times higher than that in the original medium. Combining compound mutation with rational medium optimization is an effective approach for improving tacrolimus production, and the optimized fermentation medium could be efficiently used for industrial production.

Scale-up fermentation of Escherichia coli for the production of recombinant endoglucanase from Clostridium thermocellum

Endoglucanase (EC 3.2.1.4) catalysing the hydrolysis of β-1.4-glycosidic linkage of cellulose molecules is an enzyme of tremendous industrial importance. The present study describes a response surface methodology based predicted model to deduce a set of fermentation conditions for optimum growth and activity of recombinant endoglucanase in E. coli BL21 (DE3). Numerous significant parameters including fermentation media composition, temperature (Celsius), pH and agitation rate (rpm) were analysed systemically by employing central composite design. This effort reports highly efficient recombinant endoglucanase overproduction (6.9 gl−1 of biomass) with 30% expression by E. coli in modified M9NG media incubated at 37 °C and pH 7 agitated at 200 rpm. Addition of 3 mM glucose and 24 mM glycerol in the M9NG media has shown positive effect on the enzyme yield and activity. The CMCase activity experimentally estimated was found to be 1185 U/mg with the optimized parameters. The outcomes of both the responses by the predicted quadratic model were found in consensus with the obtained values. Our results well depicted the favourable conditions to further scale-up the volumetric yield of other relevant recombinant enzymes and proteins.

New knowledge about the biosynthesis of lovastatin and its production by fermentation of Aspergillus terreus.

Lovastatin, and its semisynthetic derivative simvastatine, has great medical and economic importance, besides great potential for other uses. In the last years, a deeper and more complex view of secondary metabolism regulation has emerged, with the incorporation of cluster-specific and global transcription factors, and their relation to signaling cascades, as well as the new level of epigenetic regulation. Recently, a new mechanism, which regulates lovastatin biosynthesis, at transcriptional level, has been discovered: reactive oxygen species (ROS) regulation; also new unexpected environmental stimuli have been identified, which induce the synthesis of lovastatin, like quorum sensing-type molecules and support stimuli. The present review describes this new panorama and uses this information, together with the knowledge on lovastatin biosynthesis and genomics, as the foundation to analyze literature on optimization of fermentation parameters and medium composition, and also to fully understand new strategies for strain genetic improvement. This new knowledge has been applied to the development of more effective culture media, with the addition of molecules like butyrolactone I, oxylipins, and spermidine, or with addition of ROS-generating molecules to increase internal ROS levels in the cell. It has also been applied to the development of new strategies to generate overproducing strains of Aspergillus terreus, including engineering of the cluster-specific transcription factor (lovE), global transcription factors like the ones implicated in ROS regulation (or even mitochondrial alternative respiration aox gen), or the global regulator LaeA. Moreover, there is potential to apply some of these findings to the development of novel unconventional production systems. KEY POINTS: • New findings in regulation of lovastatin biosynthesis, like ROS regulation. • Induction by unexpected stimuli: autoinducer molecules and support stimuli. • Recent reports on culture medium and process optimization from this stand point. • Applications to molecular genetic strain improvement methods and production systems.

Biodegradation of Atrazine by Mixed Bacteria of Klebsiella variicola Strain FH-1 and Arthrobacter sp. NJ-1.

The purpose of this study is to enhance the biodegradability of atrazine with FH-1 and NJ-1 alone by selecting the mixing ratio, optimizing the culture medium and conditions. The results showed that FH-1 and NJ-1 have the best biodegradation effect on atrazine being mixed in a volume ratio of 3:2. In a single factor experiment, sucrose and NH4Cl provided carbon and nitrogen sources for the mixed bacteria. Subsequently, composition of fermentation medium was further optimized using Box-Behnken design of response surface methodology. Based on the results, growth of mixed bacteria and biodegradation of atrazine performed best effects with a biodegradation rate of 85.6% when sucrose and NH4Cl amounts were 35.30g/L and 10.28g/L. The optimal medium condition was 10% inoculum of mixed bacteria, with initial atrazine concentration of 50mg/L, neutral or weakly alkaline pH value, 30°C. The biodegradation rate reached 97.4%, 11.8% higher than the unoptimized condition.

Fungal endoinulinase production from raw Asparagus inulin for the production of fructooligosaccharides

In present study, statistical optimization of medium composition for endoinulinase production from raw inulin using Aspergillus tritici was performed in shake-flask fermentations. The concentration of four independent variables viz. raw inulin (1.5–3.5%), peptone (0.2–1.8%), (NH4)H2PO4 (0.2–1.8%) and pH (4.5–6.5) was explored to optimize the composition of fermentation medium for maximum endoinulinase production. Fermentation medium containing 2.5% raw inulin, 1% peptone, 1% (NH4)H2PO4 and medium pH adjusted to 5.5 supported maximum (25.39 IU/mL) endoinulinase production. Adequate precision value >4, closeness of coefficient of determination (R2) value to 1, good co-relation between the predicted and experimental values, percentage error <5%, high F-value 164.52 and low Lack of fit F-value 0.19 authenticates the fitness of quadratic model. TLC fingerprints studies confirmed fructooligosaccharides synthesis from inulin by crude fungal endoinulinase. Fructooligosaccharides yield (19.40%) containing 3.70% ketose (GF2), 2.71% nystose (GF3) and 1.42% fructofuranosyl nystose (GF4) were obtained from inulin (10%).

Optimization of fermentation medium for a newly isolated yeast strain (Zygosaccharomyces rouxii JM-C46) and evaluation of factors affecting biosynthesis of D-arabitol

A newly isolated yeast strain, namely Zygosaccharomyces rouxii JM-C46, was reported to be promising for enhanced D-arabitol production from glucose. In this study, further efforts were made to optimize fermentation conditions for this strain through one-factor-at-a-time strategy considering seven important factors of shake flask fermentation. Subsequently, composition of fermentation medium was optimized using Box-Behnken design (BBD) of response surface methodology (RSM) including three major nitrogen providing ingredients, namely yeast extract, (NH4)2SO4 and peptone. Maximum D-arabitol concentration produced in one-factor-at-a-time experiments was found to be 72.69 g/L under the optimum conditions consisting of 200 g/L initial glucose, 100 ml medium, 5% (equivalent to 8.78 g/L) initial inoculum, temperature 30 °C, pH 5.0, fermentation time 96 h, and agitation rate 200 rpm. In the experiments of BBD, the predicted yield of D-arabitol varied between 67.73 g/L and 76.76 g/L, while the actual concentration of D-arabitol ranged from 68.02 g/L to 76.95 g/L. The optimum composition of medium F (final medium) contained d-glucose (200 g/L), yeast extract (10 g/L), (NH4)2SO4 (2 g/L) and peptone (7.5 g/L), which further increased D-arabitol production from 72.69 g/L to 76.32 g/L.