Efficient conversion from polysialogangliosides to monosialotetrahexosylganglioside using Oerskovia xanthineolytica YZ-2

A new sialidase-producing strain isolated from soil was identified as Oerskovia xanthineolytica YZ-2. Sialidase was produced when Oerskovia xanthineolytica YZ-2 was exposed to polysialogangliosides. The sialidase of Oerskovia xanthineolytica YZ-2 hydrolyzed sialic acid linkages in polysialogangliosides, and released monosialotetrahexosylganglioside (GM1). The sialidase had the capability of product specificity because it did not attack the sialic acid linkage in GM1. Therefore, Oerskovia xanthineolytica YZ-2 was used for GM1 production from polysialogangliosides. In flasks cultivation phase, it was proved that Oerskovia xanthineolytica YZ-2 could convert polysialogangliosides to GM1 efficiently. Scaling-up the bioprocess with 8% crude ganglioside, polysialogangliosides was converted to GM1 by Oerskovia xanthineolytica YZ-2 in 30 L bioreactor after 18 h. The relative content of GM1 increased from 16.3% in crude ganglioside to 83.7% after Oerskovia xanthineolytica YZ-2 conversion. Therefore, a simple, large-scale conversion process for GM1 production from polysialogangliosides was achieved using Oerskovia xanthineolytica YZ-2 as a biocatalyst.     

Biomarkers of iron status and trace elements in welders

Iron status was studied in 137 welders exposed to a geometric mean (GM) air concentration of 214 μg/m³ (range 1–3230) of manganese (Mn), in 137 referents and in 34 former welders. The GM concentrations of S-ferritin were 119 (3–1498), 112 (9–1277) and 98 (12–989) μg/L (p = 0.24) in the three groups, respectively. Also the GM concentrations of S-hepcidin were not significantly different between the groups (8.4 μg/L (2.8–117); 6.6 μg/L (1.8–100); 6.5 μg/L (1.2–22)) (p = 0.22). Multiple linear regression analysis including all welders and referents showed an increase in the concentration of S-ferritin associated with having serum carbohydrate deficient transferrin (S-CDT) above the upper reference limit of ≥1.7%, indicating high alcohol consumption. Serum C-reactive protein was not associated with exposure as welders, but an association with S-ferritin was shown. The GM S-ferritin concentrations among all welders and referents with S-CDT ≥ 1.7% were 157 μg/L (95% CI 113–218) as compared to 104 μg/L (95% CI 94–116) (p = 0.02) in those with S-CDT < 1.7%. The GM concentrations of Mn in biological fluids were higher in the welders as compared to the referents, while S-Fe, S-Co and B-Co were statistically significantly lower. This could suggest a competitive inhibition from Mn on the uptake of Fe and Co. Increasing concentrations of S-CDT was associated with higher S-Mn, S-Fe and B-Co in the multiple linear regression analysis. The association between S-CDT and S-Fe remained when all subjects with high S-CDT (≥1.7%) were excluded, suggesting increased uptake of Fe even at lower alcohol consumption.     

The blood lead levels of outpatients aged 1–18 years from Lu’an,China, 2012–2014

To evaluate blood lead levels (BLLs) and possible influencing factors among children and adolescents in Lu’an, we collected blood samples of 3266 outpatients aged 1–18 years from January 2012 to December 2014 and BLLs were determined by atomizer absorption spectrophotometer. The results showed that the geometric mean (GM) of BLLs was 29.53 μg/L (95% CI: 29.00–30.06 μg/L) and the prevalence of BLLs ≥50 and 100 μg/L were 17.7% and 0.2%, respectively. The GM BLLs and prevalence of BLLs ≥50 μg/L were increased with age before 7 years old and then slightly decreased, and, contrary to previous studies, they were the highest at Jan–Feb and the lowest at Sep–Oct. From 2012 to 2014, the GM BLLs were significantly increased (P < 0.001) while the prevalence of BLLs ≥50 μg/L was decreased but with no significant difference (P > 0.05). These results suggested that although the BLLs of Lu’an children were lower than most areas of China and several neighboring cities as previously reported, they were still higher than that of developed countries. Meanwhile, the GM BLLs of children and adolescents from Lu’an have a trend of increase in recent years. A lot of future works need to be done to identify the risk factors for lead exposure.     

Decreased serum level of IL-7 in patients with active Graves’ disease

BackgroundGraves’ disease (GD) is a common autoimmune disease which is one of the major causes of hyperthyroidism. Interleukin 7 (IL-7) has been recently reported to play an important role in various autoimmune diseases, but its role in the pathogenesis of GD has not been assessed. The aim of this study was to evaluate the levels of IL-7 and the soluble form of its receptor (sIL-7R) in the serum of GD patients, and to identify their association with disease activity.MethodsA total of 37 GD patients were enrolled into the experimental group and 16 individuals into the control group. All patients were further classified into three subgroups: a GD-active group (hyperthyroidism and TRAb (thyroid stimulating hormone receptor antibody) >7.5 U/L) (N = 15), a GD-inactive group (euthyreosis and TRAb < 1 U/L) (N = 8), and other GD patients (euthyreosis and TRAb > 1 U/L) (N = 14). Concentrations of IL-7 and sIL-7R were assayed with ELISA. Additionally, the relationship between IL-7 and sIL-7R serum concentrations with disease activity (free triiodothyronine [FT3], free thyroxine [FT4], thyroid stimulating hormone [TSH] and TRAb) was also analyzed.ResultsThe serum concentrations of IL-7 in GD-active patients were significantly lower than those of the control group as well as the GD-inactive and GD-other groups. The serum level of IL-7 in GD patients negatively correlated with FT4 and TRAb concentrations. Moreover, no significant difference was observed in the serum level of sIL-7R in GD patients compared to the control group.ConclusionsThese observations suggest that IL-7 may play a role in the pathogenesis of GD and may be associated with its clinical activity. To this end, the serum level of IL-7 could be an additional diagnostic biomarker predictive of the disease and could be particularly valuable for TRAb-negative GD patients.     

Production of fructooligosaccharides by mycelium-bound transfructosylation activity present in Cladosporium cladosporioides and Penicilium sizovae

Different filamentous fungi isolated from molasses and jams (kiwi and fig) were screened for fructooligosaccharides (FOS) producing activity. Two strains, identified as Penicilium sizovae (CK1) and Cladosporium cladosporioides (CF₂15), were selected on the basis of the FOS yield and kestose/nystose ratio. In both strains the activity was mostly mycelium-bound. Starting from 600 g/L of sucrose, maximum FOS yield was 184 and 339 g/L for P. sizovae and C. cladosporioides, respectively. Interestingly, the highest FOS concentration with C. cladosporioides was reached at 93% sucrose conversion, which indicated a notable transglycosylation to hydrolysis ratio. The main FOS in the reaction mixtures were identified by HPAEC–PAD chromatography. C. cladosporioides synthesized mainly 1-kestose (158 g/L), nystose (97 g/L), ¹F-fructosylnystose (19 g/L), 6-kestose (12 g/L), neokestose (10 g/L) and a disaccharide (34 g/L) that after its purification and NMR analysis was identified as blastose [Fru-β(2 → 6)-Glc]. P. sizovae was very selective for the formation of ¹F-FOS (in particular 1-kestose) with minor contribution of neoFOS and negligible of levan-type FOS.     

Bioactivity of essential oil of Litsea cubeba from China and its main compounds against two stored product insects

During our screening program for agrochemicals from Chinese medicinal herbs and wild plants, the essential oil of Litsea cubeba fruits was found to possess strong contact toxicity against the cigarette beetle Lasioderma serricorne adults and the booklouse Liposcelis bostrychophila, with LD₅₀ values of 27.33 μg/adult and 71.56 μg/cm², respectively, and also showed strong fumigant toxicity against the two stored product insects with LC₅₀ values of 22.97 and 0.73 mg/L, respectively. The essential oil obtained by hydrodistillation was investigated by GC MS. The main components of the essential oil were identified to be E-citral (geranial) (27.49%), Z-citral (neral) (23.57%) and d-limonene (18.82%) followed by β-thujene (3.34%), β-pinene (2.85%), α-pinene (2.57%), 6-methyl-5-hepten-2-one (2.40%) and linalool (2.36%). Citral (Z/E-citral), d-limonene, β-pinene, α-pinene and linalool were separated and purified by silica gel column chromatography and preparative thin layer chromatography, and further identified by means of physicochemical and spectrometric analysis. Citral and linalool showed strong contact toxicity against L. serricorne and L. bostrychophila (LD₅₀ = 11.76, 12.74 μg/adult and 20.15, 99.97 μg/cm², respectively) and fumigant toxicity against L. serricorne and L. bostrychophila (16.54, 18.04 mg/L air and 0.14, 0.71 mg/L air, respectively). Otherwise, citral, d-limonene and linalool were strongly repellent against the cigarette beetle L. serricorne as the essential oil whereas β-pinene and α-pinene exhibited weaker repellency against the cigarette beetle compared with the positive control, DEET. Moreover, except α-pinene and linalool, the other three compounds as well as the essential oil exhibited comparable repellency against the booklouse relative to DEET.     

Effect of modified MRS medium on production and purification of antimicrobial peptide ST4SA produced by Enterococcus mundtii

Highest antimicrobial activity of peptide ST4SA (51,200 AU/mL) was recorded after 14 h of growth in MRS broth with optimal production at pH 6.0 or 6.5. Growth of strain ST4SA in the presence of tryptone, yeast extract, or a combination of the two, yielded 102,400 AU/mL. An increase in production of peptide ST4SA to 102,400 AU/mL was recorded in the presence of 20.0 g/L fructose, but decreased to 25,600 AU/mL in the presence of lactose (20.0 g/L) or mannose (20.0 g/L) as sole carbon source. Lower activity (25,600 AU/mL) was recorded when 2.0 g/L K₂HPO₄ was replaced by 2.0 g/L KH₂PO₄ in MRS broth. An increase of K₂HPO₄ to 10.0 g/L and 20.0 g/L resulted in higher activity (102,400 AU/mL). Addition of glycerol to MRS broth had a negative effect on peptide ST4SA production. Production of peptide ST4SA required the presence of magnesium sulphate, manganese sulphate and 5.0 g/L sodium acetate. Exclusion of tri-ammonium citrate from the medium resulted in reduction of activity to 3,200 AU/mL. Maximum activity (102,400 AU/mL) was recorded in MRS supplemented with 1.0 ppm Vit. C, DL-6,8-thioctic acid or thiamine, respectively. Growth of Listeria ivanovii susbp. ivanovii ATCC 19119 in the presence of peptide ST4SA (12,800 AU/mL) resulted in 99% cell lysis after 18 h. Improved production of peptide ST4SA was recorded in MRS broth (Biolab) pre-treated with Amberlite XAD-1180. Precipitation with ammonium sulphate, followed by gel filtration chromatography, yielded the highest level of peptide ST4SA. This paper describes the partially deproteination of growth medium to facilitate peptide ST4SA purification.     

Development of new ganglioside probes and unraveling of raft domain structure by single-molecule imaging

Gangliosides are involved in a variety of biological roles and are a component of lipid rafts found in cell plasma membranes (PMs). Gangliosides are especially abundant in neuronal PMs and are essential to their physiological functions. However, the dynamic behaviors of gangliosides have not been investigated in living cells due to a lack of fluorescent probes that behave like their parental molecules. We have recently developed, using an entirely chemical method, four new ganglioside probes (GM1, GM2, GM3, and GD1b) that act similarly to their parental molecules in terms of raft partitioning and binding affinity. Using single fluorescent-molecule imaging, we have found that ganglioside probes dynamically enter and leave rafts featuring CD59, a GPI-anchored protein. This occurs both before and after stimulation. The residency time of our ganglioside probes in rafts with CD59 oligomers was 48 ms, after stimulation. The residency times in CD59 homodimer and monomer rafts were 40 ms and 12 ms, respectively. In this review, we introduce an entirely chemical-based ganglioside analog synthesis method and describe its application in single-molecule imaging and for the study of the dynamic behavior of gangliosides in cell PMs. Finally, we discuss how raft domains are formed, both before and after receptor engagement. This article is part of a Special Issue entitled Neuro-glycoscience, edited by Kenji Kadomatsu and Hiroshi Kitagawa.     

Changes of ginsenosides in Korean red ginseng (Panax ginseng) fermented by Lactobacillus plantarum M1

To obtain microorganisms for the microbial conversion of ginsenosides in red ginseng powder (RGP), Lactobacillus species (M1–M4 and P1–P4) were isolated from commercial ginseng products. Strain M1 was determined to be L. plantarum by 16S rRNA sequencing. Red ginseng powder (RGP) fermented by L. plantarum M1 had a high total content of ginsenosides (142.4 mg/g) as compared to the control (121.8 mg/g). In particular, the ginsenoside metabolites Rg3, Rg5, Rk1, Compound K (CK), Rh1, and Rg2 showed a high level in the fermented RGP (65.5 mg/g) compared to the control (32.7 mg/g). During fermentation for 7 days, total sugar content decreased from 8.55 mg/g to 4 mg/g, uronic acid content reached its maximum (53.43 μg/g) at 3 days, and total ginsenoside content increased to 176.8 mg/g at 4 days. In addition, ginsenoside metabolites increased from 38.0 mg/g to 83.4 mg/g at 4 days of fermentation. Using everted instestinal sacs of rats, the fermented red ginseng showed a high transport level (10.3 mg of polyphenols/g sac) compared to non-fermented red ginseng (6.67 mg of polyphenols/g sac) after 1 h. These results confirm that fermentation with L. plantarum M1 is very useful for preparing minor ginsenoside metabolites while being safe for foods.     

Structure,properties and applications of rhamnolipids produced by Pseudomonas aeruginosa L2-1 from cassava wastewater

The properties and applications of rhamnolipid surfactants produced by Pseudomonas aeruginosa L2-1 from cassava wastewater added with waste cooking oil (CWO) as low-cost substrate, were investigated and compared with the commercial rhamnolipid mixture JBR599 (Jeneil Biosurfactant Co., Saukville, USA). The rhamnolipids produced by strain L2-1 were characterized by high performance liquid chromatography–mass spectrometry. Sixteen different rhamnolipid congeners were detected, with Rha-C₁₀-C₁₀ and Rha-Rha-C₁₀-C₁₀ being the most abundant. The L2-1 rhamnolipids from CWO showed similar or better tensioactive properties than those from JBR599, with a minimal surface tension of 30 mN/m and a critical micelle concentration (CMC) of 30 mg/l. The L2-1 biosurfactants formed stable emulsions with several hydrocarbons and showed excellent emulsification of soybean oil (100%). These rhamnolipids removed 69% of crude oil present in contaminated sand samples at the CMC and presented antimicrobial activity against Bacillus cereus (32 μg/ml), Micrococcus luteus (32 μg/ml) and Staphylococcus aureus (128 μg/ml). These results demonstrate that the rhamnolipids produced in CWO can be useful for industrial applications, such as the bioremediation of oil spills.     

Directed bioconversion of Kraft lignin to polyhydroxyalkanoate by Cupriavidus basilensis B-8 without any pretreatment

This work presents here a new fundamental strategy for bio-converting Kraft lignin (KL) into useful products. Cupriavidus basilensis B-8 (here after B-8) was able to use KL as the sole carbon source. Fully 41.5% of lignin, 37.7% of total carbon (TC) and 43.0% of color were removed after 7 days of incubation. At the same time, lignin was depolymerized into small fragments, which was confirmed by scanning electron microscopy (SEM) and gel permeation chromatography (GPC). Bacterial biomass accumulated to 735.6 mg/L at the initial KL concentration of 5 g L⁻¹, and the corresponding volumetric productivity of polyhydroxyalkanoate (PHA) was 128 mg/L. PHA productivity was significantly improved through fed batch fermentation and reached to 319.4 mg/L. GC–MS analysis showed that PHA polymer was composed of three basic monomers: 98.3 mol% of (S)-3-hydroxy-butanoic acid (S3HB), 1.3 mol% of ^®-3-hydroxybutyric acid (R3HB) and 0.4 mol% of 3-hydroxy-butanoic acid (3HB).     

Dried alginate-entrapped enzymes (DALGEEs) and their application to the production of fructooligosaccharides

A modification of the classical calcium alginate enzyme entrapment technique is described aiming to overcome some of the limitations of the former gel-based biocatalysts. Dried alginate entrapped enzymes (DALGEEs) were obtained dehydrating calcium alginate gel beads containing entrapped enzymes. A fructosyltransferase from Aspergillus aculeatus, present in Pectinex Ultra SP-L, was entrapped using this technique. The resulting DALGEEs were successfully tested both operating batchwise and in a continuous fixed-bed reactor for fructooligosaccharides (FOS) synthesis from sucrose. Interestingly, DALGEEs did not re-swell upon incubation in concentrated (600 g/L) sucrose solutions, probably due to the lowered water activity (a_w) of such media. Confocal laser scanning microscopy of DALGEEs revealed that the enzyme molecules accumulated preferably in the shell of the particles. DALGEEs showed an approximately 30-fold higher volumetric activity (300 U/mL) compared with the calcium alginate gel beads. Moreover, a significant enhancement (40-fold) of the space-time-yield of fixed-bed bioreactors was observed when using DALGEEs as biocatalyst compared with gel beads (4030 g/day L of FOS vs. 103 g/day L). The operational stability of fixed-bed reactors packed with DALGEEs was extraordinary, providing a nearly constant FOS composition of the outlet during at least 700 h. It was also noticeable their resistance against microbial attack, even after long periods of storage at room temperature. The DALGEEs immobilisation strategy may also be useful for other biotransformations, in particular when they take place in low a_w media.     

l-NAME prevents GM1 ganglioside-induced vasodilation in the rat brain

Monosialoganglioside (GM1) is a glycosphingolipid present in most cell membranes that displays antioxidant and neuroprotective properties. It has been recently described that GM1 induces vasodilation. However, the mechanisms underlying GM1-induced vasodilation were not evaluated to date. Therefore, in this study we investigated whether the nonspecific NOS inhibitor l-NAME prevents GM1-induced vasodilation in rats. The systemic injection of GM1 (50 mg/kg, i.p.) increased the outer diameter of pial vessels by 50% in anesthetized animals at 30 min, and this effect was fully prevented by the administration of the nitric oxide synthase inhibitor N^G-nitro-l-arginine methyl ester (l-NAME, 60 mg/kg, i.p. 15 min before GM1 injection).A 30 min exposure of cerebral cortex slices to GM1 (100 μM) increased the content of nitrite plus nitrate (NOx) by 50%. Addition of l-NAME (100 μM) to the incubation medium fully prevented GM1-induced NOx increase. Conversely, a 60 min exposure of slices to GM1 (100 μM) decreased NOx content, revealing a biphasic effect of GM1. Our results suggest that NO plays an important role in the vasodilation induced by GM1.     

Metabolic engineering of Escherichia coli for the production of 5-aminovalerate and glutarate as C5 platform chemicals

5-Aminovalerate (5AVA) is the precursor of valerolactam, a potential building block for producing nylon 5, and is a C5 platform chemical for synthesizing 5-hydroxyvalerate, glutarate, and 1,5-pentanediol. Escherichia coli was metabolically engineered for the production of 5-aminovalerate (5AVA) and glutarate. When the recombinant E. coli WL3110 strain expressing the Pseudomonas putida davAB genes encoding delta-aminovaleramidase and lysine 2-monooxygenase, respectively, were cultured in a medium containing 20 g/L of glucose and 10 g/L of l-lysine, 3.6 g/L of 5AVA was produced by converting 7 g/L of l-lysine. When the davAB genes were introduced into recombinant E. coli strainXQ56allowing enhanced l-lysine synthesis, 0.27 and 0.5 g/L of 5AVA were produced directly from glucose by batch and fed-batch cultures, respectively. Further conversion of 5AVA into glutarate could be demonstrated by expression of the P. putida gabTD genes encoding 5AVA aminotransferase and glutarate semialdehyde dehydrogenase. When recombinant E. coli WL3110 strain expressing the davAB and gabTD genes was cultured in a medium containing 20 g/L glucose, 10 g/L l-lysine and 10 g/L α-ketoglutarate, 1.7 g/L of glutarate was produced.     

DNA damage induction and antiproliferative activity of vanadium(V) oxido monoperoxido complex containing two bidentate heteroligands

Several peroxidovanadium(V) complexes have been shown as a potent anticancer agents. The aim of this study was to investigate the interaction of monoperoxidovanadium(V) complex Pr₄N[VO(O₂)(ox)(phen)], (Vphen), [phen = 1,10-phenantroline, ox = oxalate(2?) and Pr₄N = tetra(n-propyl)ammonium(1+)] with DNA. UV–Vis spectrophotometry and the alkaline single-cell gel electrophoresis (SCGE, the comet assay) were used to examine the possibility of the vanadium(V) complex to induce changes in DNA. The interaction of Vphen with calf thymus DNA resulted in absorption hyperchromicity in DNA spectrum and shift of the absorption band of DNA to longer wavelengths for the [complex]/[DNA] concentration ratio equals to 4 and after 60 min of incubation. The rise in DNA absorption (by 34%) and bathochromic shift (Δλ_max = 6 nm) are indicative of the interaction between DNA and the complex molecules. DNA strand breaks in cellular DNA were investigated using the comet assay. The human lymphocytes were exposed to various concentrations of Vphen for 30 min. The results revealed that Vphen contributed to the DNA damage expressed as DNA strand breaks in concentration dependent manner. The used concentrations of Vphen (ranging from 0.1 to 100 μmol/L) caused higher DNA damage in lymphocytes compared to untreated cells (from 1.2 times for 0.1 μmol/L to 1.8 times for 100 μmol/L). Vphen was screened for its potential antitumor activity towards murine leukemia cell line L1210. Vphen exhibited significant antiproliferative activity depending on its concentration and time of exposure. The IC₅₀ values were 0.247 μg/mL (0.45 μmol/L) for 24 h, 0.671 μg/mL (1.21 μmol/L) for 48 h and 0.627 μg/mL (1.13 μmol/L) for 72 h.     

Use of Saccharum spontaneum (wild sugarcane) as biomaterial for cell immobilization and modulated ethanol production by thermotolerant Saccharomyces cerevisiae VS3

Saccharum spontaneum is a wasteland weed consists of 45.10 ± 0.35% cellulose and 22.75 ± 0.28% of hemicellulose on dry solid (DS) basis. Aqueous ammonia delignified S. spontaneum yielded total reducing sugars, 53.91 ± 0.44 g/L (539.10 ± 0.55 mg/g of substrate) with a hydrolytic efficiency of 77.85 ± 0.45%. The enzymes required for hydrolysis were prepared from culture supernatants of Aspergillus oryzae MTCC 1846. A maximum of 0.85 ± 0.07 IU/mL of filter paperase (FPase), 1.25 ± 0.04 IU/mL of carboxy methyl cellulase (CMCase) and 55.56 ± 0.52 IU/mL of xylanase activity was obtained after 7 days of incubation at 28 ± 0.5 °C using delignified S. spontaneum as carbon source under submerged fermentation conditions. Enzymatic hydrolysate of S. spontaneum was then tested for ethanol production under batch and repeated batch production system using “in-situ” entrapped Saccharomyces cerevisiae VS₃ cells in S. spontaneum stalks (1 cm × 1 cm) size. Immobilization was confirmed by the scanning electron microscopy (SEM). Batch fermentation of VS₃ free cells and immobilized cells showed ethanol production, 19.45 ± 0.55 g/L (yield, 0.410 ± 0.010 g/g) and 21.66 ± 0.62 g/L (yield, 0.434 ± 0.021 g/g), respectively. Immobilized VS₃ cells showed maximum ethanol production (22.85 ± 0.44 g/L, yield, 0.45 ± 0.04 g/g) up to 8th cycle during repeated batch fermentation followed by a gradual reduction in subsequent cycles of fermentation.     

Enhanced acetone/butanol/ethanol production by Clostridium beijerinckii IB4 using pH control strategy

PH is an essential factor for acetone/butanol/ethanol (ABE) production using Clostridium spp. In this study, batch fermentations by Clostridium beijerinckii IB4 at various pH values ranging from 4.9 to 6.0 were examined. At pH 5.5, the ABE production was dominant and maximum ABE concentration of 24.6 g/L (15.7 g/L of butanol, 8.63 g/L of acetone and 0.32 g/L of ethanol) was obtained with the consumption of 60 g/L of glucose within 36 h. However, in the control (without pH control), an ABE concentration of 14.1 g/L (11.0 g/L of butanol, 3.01 g/L of acetone and 0.16 g/L of ethanol) was achieved with the consumption of 41 g/L of glucose within 40 h. A considerable improvement in the productivity of up to 93.8% was recorded at controlled pH in comparison to the process without pH control. To better understand the influence of pH on butanol production, the reducing power capability and NADH-dependent butanol dehydrogenase activity were investigated, both of which were significantly improved at pH 5.5. Thus, the pH control technique is a convenient and efficient method for high-intensity ABE production.     

Kinetic modeling and implementation of superior process strategies for β-galactosidase production during submerged fermentation in a stirred tank bioreactor

This paper reports development and implementation of superior fermentation strategies for β-galactosidase production by Lactobacillus acidophilus in a stirred-tank bioreactor. Process parameters (aeration and agitation) were optimized for the process by application of Central Composite Design. Aeration rate of 0.5 vvm and agitation speed of 250 rpm were most suitable for β-galactosidase production (2001.2 U/L). Further improvement of the operation in pH controlled environment resulted in 2135 U/L of β-galactosidase with productivity of 142.39 U/L h. Kinetic modeling for biomass and enzyme production and substrate utilization were carried out at the aforementioned pH controlled conditions. The logistic regression model (X₀ = 0.01 g/L; X_max = 2.948 g/L; μ_max = 0.59/h; R² = 0.97) was used for mathematical interpretation of biomass production. Mercier's model proved to be better than Luedeking–Piret model in describing β-galactosidase production (P₀ = 0.7942 U/L; P_max = 2169.3 U/L; P_r = 0.696/h; R² = 0.99) whereas the latter was more efficient in mathematical illustration of lactose utilization (m = 0.187 g/g h; Y_x/s = 0.301 g/L; R² = 0.98) among the two used in this study. Strategies like fed-batch fermentation (3694.6 U/L) and semi-continuous fermentation (5551.9 U/L) further enhanced β-galactosidase production by 1.8 and 2.8 fold respectively.     

A simple approach for the selective enzymatic synthesis of dilauroyl maltose in organic media

A selective synthesis of dilauroyl maltose was developed using lipase-catalyzed condensation of lauric acid and maltose in two-solvent mixtures. The characteristics of different solvent combination were tested and it was found that the combination of acetone with n-hexane has a good selectivity for the synthesis of dilauroyl maltose. The highest diester conversion of 69% (i.e. 36.5 g/L of dilauroyl maltose) was obtained under optimal conditions: 25.65 g/L maltose, 60 g/L lauric acid, 60 g/L molecular sieve and 10 g/L lipase at 150 rpm and 50 °C for 72 h in 10 mL of mixed solvent of acetone:n-hexane (60:40, v/v).     

Enhancing production of prodigiosin from Serratia marcescens C3 by statistical experimental design and porous carrier addition strategy

Serratia marcescens C3 produces a natural red-pigment, prodigiosin, which exhibits immunosuppressive properties, in vitro apoptotic effects, and in vivo anti-tumor activities. This work seeks to improve the production of prodigiosin by S. marcescens C3 using various strategies. Starch and peptone were identified as the optimized carbon and nitrogen sources for the production of prodigiosin, yielding a prodigiosin concentration of 2.3 g/L. This value was significantly increased to 6.7 g/L using a carbon/nitrogen ratio of 6/4 (starch/peptone = 16 g/L/10.67 g/L). To enhance prodigiosin production even further, a statistical experimental design methodology was utilized to optimize the composition of the culture medium that is utilized in the production of prodigiosin. Prodigiosin production of 7.07 g/L was achieved when the concentrations of two trace compounds, FeSO₄·4H₂O and MnSO₄·4H₂O, were optimized using the statistical experimental design methodology. Their optimal concentrations were 0.56 mM and 3.25 mM, respectively. Ultimately, the production of prodigiosin was increased from 2.3 g/L to 15.6 g/L, or by a factor of nearly seven by immobilizing microorganisms in 3% calcium alginate beads.