Optimal Glucose Concentration Research Articles

Optimization of the fermentative production of L-methionine by engineered Escherichia coli

As the only essential amino acid containing elemental sulphur, L-methionine has important physiological and biochemical functions in living organisms. However, the fermentative production of L-methionine has not met the requirements of industrial production because of its low production level. In this paper, the fermentation process of an efficient L-methionine producing strain E. coli W3110ΔIJAHFEBC trc-fliY trc-malY/PAM glyA-22 metF constructed previously was systematically optimized. Based on the optimal initial glucose concentration, the effects of different fed-batch fermentation processes, including DO-Stat, pH-Stat, controlling residual sugar control at different level and feeding glucose with constant rate, on L-methionine fermentation were studied. It was found that the control of glucose concentration greatly affected the fermentation process. Subsequently, an optimal fed-batch fermentation process was developed, where the L-methionine titer was increased to 31.71 g/L, the highest yield reported to date, while the fermentation time was shortened to 68 h. Meanwhile, a fermentation kinetics model under the optimal fed-batch fermentation conditions was established, which fitted well with the biosynthesis process of L-methionine. This study may facilitate further development of the fermentative production of L-methionine.

In situ adsorption of itaconic acid from fermentations of Ustilago cynodontis improves bioprocess efficiency

BackgroundReducing the costs of biorefinery processes is a crucial step in replacing petrochemical products by sustainable, biotechnological alternatives. Substrate costs and downstream processing present large potential for improvement of cost efficiency. The implementation of in situ adsorption as an energy-efficient product recovery method can reduce costs in both areas. While selective product separation is possible at ambient conditions, yield-limiting effects, as for example product inhibition, can be reduced in an integrated process.ResultsAn in situ adsorption process was integrated into the production of itaconic acid with Ustilago cynodontis IAmax, as an example of a promising biorefinery process. A suitable feed strategy was developed to enable efficient production and selective recovery of itaconic acid by maintaining optimal glucose concentrations. Online monitoring via Raman spectroscopy was implemented to enable a first process control and understand the interactions of metabolites with the adsorbent. In the final, integrated bioprocess, yield, titre, and space–time yield of the fermentation process were increased to values of 0.41 gIA/gGlucose, 126.5 gIA/L and 0.52 gIA/L/h. This corresponds to an increase of up to 30% in comparison to the first extended batch experiment without in situ product removal. Itaconic acid was recovered with a purity of at least 95% and high concentrations above 300 g/L in the eluate.ConclusionIntegration of product separation via adsorption into the bioprocess was successfully conducted and improved the efficiency of itaconic acid production. Raman spectroscopy was proven to be a reliable tool for online monitoring of various metabolites and facilitated design and validation of the complex separation and feed process. The general process concept can be transferred to the production of various similar bioproducts, expanding the tool kit for design of innovative biorefinery processes.

Perioperative glycaemic control for people with diabetes undergoing surgery.

Perioperative glycaemic control for people with diabetes undergoing surgery.

Utilization of Meat and Bone Meal for Yeast Fermentation to Produce Astaxanthin

Meat and bone meal (MBM) is a product of the rendering industry, which is looking for high-value applications of rendered animal proteins (RAP). The objective of this research was to utilize MBM as a nitrogen source to produce astaxanthin (AX) by Xanthophyllomyces dendrorhous and quantify the bioavailability of MBM as a potential substitution of commercial nitrogen sources (i.e., yeast extract and peptone). To conduct yeast fermentation under the optimal glucose loading, the C/N ratio was optimized to achieve maximum AX content. MBM was hydrolyzed by using proteinase and alkaline (Ca(OH)2) for 4, 8, and 16 h with different enzyme and alkaline loadings to produce MBM hydrolysates (MBMHs). The MBMHs were directly fermented by X. dendrorhous under the optimum glucose concentration. Experimentally, the optimum medium contained 40 g/L glucose, 5 g/L peptone, and 3 g/L yeast extract, where AX content of 3.69 mg/g dry cell mass was achieved. MBMHs were used by X. dendrorhous as a nitrogen source, while fermentation with lyophilized MBMHs was generated using proteinase K. This resulted in a maximum AX content of 1.58 mg/g dry cell mass. This research exhibits the feasibility of using MBM as a nitrogen source to produce AX with X. dendrorhous.

Cerebral Glucose Concentration in Neonatal Hypoxic–Ischemic Encephalopathy during Therapeutic Hypothermia

To determine cerebral glucose concentration and its relationship with glucose infusion rate (GIR) and blood glucose concentration in neonatal encephalopathy during therapeutic hypothermia (TH). This was an observational study in which cerebral glucose during TH was quantified by magnetic resonance (MR) spectroscopy and compared with mean blood glucose at the time of scan. Clinical data (gestational age, birth weight, GIR, sedative use) that could affect glucose use were collected. The severity and pattern of brain injury on MR imaging were scored by a neuroradiologist. Student t test, Pearson correlation, repeated measures ANOVA, and multiple regression analysis were performed. Three-hundred-sixty blood glucose values and 402MR spectra from 54 infants (30 female infants; mean gestational age 38.6± 1.9weeks) were analyzed. In total, 41 infants had normal-mild and 13 had moderate-severe injury. Median GIR and blood glucose during TH were 6.0mg/kg/min (IQR 5-7) and 90mg/dL (IQR 80-102), respectively. GIR did not correlate with blood or cerebral glucose. Cerebral glucose was significantly greater during than after TH (65.9± 22.9 vs 60.0± 25.2mg/dL, P<.01), and there was a significant correlation between blood glucose and cerebral glucose during TH (basal ganglia: r=0.42, thalamus: r=0.42, cortical gray matter: r=0.39, white matter: r=0.39, all P<.01). There was no significant difference in cerebral glucose concentration in relation to injury severity or pattern. During TH, cerebral glucose concentration is partly dependent on blood glucose concentration. Further studies to understand brain glucose use and optimal glucose concentrations during hypothermic neuroprotection are needed.

Utilization of corncob waste as bioethanol raw material by activities of Dekkera Bruxellensis and Saccharomyces Cerevisiae

Corncob waste is not managed properly has the potential to environmental pollution. The purpose of this reasearch is to utilize corncob waste as a potential biomass into bioethanol. Process of making bioethanol is carried out in 4 steps, namely delignification, hydrolysis, fermentation, distillation. Corncob as substrate were prepared mechanically to become size powder 40 mesh. Delignification by fungi Dekkera Bruxellensis was varied with substrate ratio of 5, 10, and 15 grams at contact times of 3, 5, and 7 days. Hydrolysis with 2% sulfuric acid (H2SO4) at contact times of 30, 45, and 60 minutes. Glucose concentration was measured uing 3, 5-dinitrosalicylate (DBS) method. Variations of fungi:ragi = 1:1 at contact times of 3, 5, and 7 days. Distillation at temperature of 78°C using Gas Chromatography–Mass Spectrophotometry (GC-MS). This result in optimum delignification at substrate variation of 5 grams at contact time of 7 days, with a lignin removal 20,72%. The optimum glucose concentration in hydrolysis produced 7,561 g/L glucose at 2% Sulfuric acid (H2SO4). The highest ethanol content of 2,95% occured in ratio fungi:yeast 1:1 with substrate of 5 grams during 7 days. Based on pilot scale calculation with diameter 1,9 m and height of 0,9 m, then for 100 kg of corncobs can be produce 4,133L total ethanol.

Development of Solid Lipid Nanoparticles as Dry Powder: Characterization and Formulation Considerations.

Solid lipid nanoparticles (SLNs) are lipid-based colloidal systems used for the delivery of active compounds. Although SLNs have many benefits, they show important issues due to physical and chemical instability phenomena during storage. For these reasons, it is highly desirable to have a dried SLN formulation available. Therefore, the aim of the project was to identify suitable methods to obtain a dry powder formulation from an SLN suspension. The nanoparticle suspension was dried using both freeze- and spray-drying techniques. The suitability of these methods in obtaining SLN dry powders was evaluated from the analyses of nanotechnological parameters, system morphology and thermal behavior using differential scanning calorimetry. Results pointed out that both drying techniques, although at different yields, were able to produce an SLN dry powder suitable for pharmaceutical applications. Noteworthily, the freeze-drying of SLNs under optimized conditions led to a dry powder endowed with good reconstitution properties and technological parameters similar to the starting conditions. Moreover, freeze-thaw cycles were carried out as a pretest to study the protective effect of different cryoprotectants (e.g., glucose and mannitol with a concentration ranging from 1% to 10% w/v). Glucose proved to be the most effective in preventing particle growth during freezing, thawing, and freeze-drying processes; in particular, the optimum concentration of glucose was 1% w/v.

Lipid accumulation by a novel microalga Parachlorella kessleri R-3 with wide pH tolerance for promising biodiesel production

In this study, a new microalgal strain was isolated and identified as Parachlorella kessleri R-3, which could utilize a variety of organic and inorganic carbon and nitrogen sources. More importantly, it was found that strain R-3 can accumulate large amount of biomass and lipids in a wide pH range from 3 to 11, and it can gradually adjust the pH of the medium to near neutrality during the cultivation. At the optimal glucose concentration of 10 g L−1, sodium nitrate concentration of 0.8 g L−1 and initial pH of 7, the highest algal biomass of 6.90 g L−1, lipid content of 45.12 % and lipid productivity of 340.94 mg L−1 d−1 were achieved. In addition, C16:0 iso 3OH and C16:1 w7c alcohol were the predominant fatty acids components, which accounted for as high as 88.04 %. These showed the potential of the new microalgal strain for application in biodiesel production.

Solid-state fermentation produces greater stearidonic acid levels in genetically engineered Mucor circinelloides.

Omega-3 (ω-3) polyunsaturated fatty acids (PUFAs) are important dietary components due to their health benefits and preventative role in cardiovascular disease. Fish-based and plant seed oils are rich in stearidonic acid (SDA; 18:4, n-3), which are readily metabolized into ω-3 PUFAs such as eicosapentaenoic acid. However, these natural sources of SDA are generally low yielding and are unlikely to meet global demands, so new sustainable microbial fermentative sources of SDA need to be identified. Expression of delta15-desaturase in the oleaginous filamentous fungus Mucor circinelloides (McD15D) has been used to construct a recombinant SDA-producing McD15D strain that produces 5·0% SDA levels using submerged fermentation conditions. Switching to solid-state fermentation conditions in the same medium with submerged fermentation resulted in this engineered strain producing significantly higher amounts of SDA. A Box-Behnken design of response surface methodology approach has been used to identify optimal glucose and ammonium tartrate concentrations and temperature levels to maximize SDA production. The use of these optimal solid-state fermentation conditions resulted in the spores and mycelium of the recombinant McD15D producing 19·5% (0·64 mg g-1 ) and 12·2% (1·52 mg g-1 ) SDA content, respectively, which represents an overall increase in SDA yield of 188·0% compared with SDA yields produced using submerged fermentation conditions.

Effects of Glucose and Homogenization Treatment on the Quality of Liquid Whole Eggs

To investigate the effect of glucose on the protein structure, physicochemical and processing properties of liquid whole eggs (LWE) under homogenization, different concentrations of glucose (0.01, 0.02, 0.04, 0.08 g/mL) were added into LWE, followed by homogenizing at different pressures (5, 10, 20, 40 MPa), respectively. It was shown that the particle size and turbidity of LWE increased with the increase in glucose concentration while decreasing with the increase in homogenization pressure. The protein unfolding was increased at a low concentration of glucose combined with homogenization, indicating a 40.33 ± 5.57% and 165.72 ± 33.57% increase in the fluorescence intensity and surface hydrophobicity under the condition of 0.02 g/mL glucose at 20 MPa, respectively. Moreover, the remarkable increments in foaming capacity, emulsifying capacity, and gel hardness of 47.57 ± 5.1%, 66.79 ± 9.55%, and 52.11 ± 9.83% were recorded under the condition of 0.02 g/mL glucose at 20 MPa, 0.04 g/mL glucose at 20 MPa, and 0.02 g/mL glucose at 40 MPa, respectively. Reasonably, glucose could improve the processing properties of LWE under homogenization, and 0.02 g/mL–0.04 g/mL and 20–40 MPa were the optimal glucose concentration and homogenization pressure. This study could contribute to the production of high-performance and stable quality of LWE.

Glycemic Control for Type 2 Diabetes Mellitus Patients: A Systematic Review

Diabetes mellitus is a chronic metabolic disorder resulting in hyperglycemia and microvascular and macrovascular complications in individuals globally. Type 2 diabetes mellitus (T2DM) is highly prevalent and accounts for 90% of patients. Maintaining blood glucose concentration is essential to avoid severe complications.Glycemic control is the optimal serum glucose concentration in diabetic patients. It is necessary to identify factors affecting the glycemic control of patients to prevent control and complications. We conducted this systematic review to assess the factors affecting glycemic control among type 2 diabetes mellitus patients.Published literature between the years 2020 to 2022 was retrieved from PubMed, Science Direct, and Google Scholar using different combinations of keywords: T2DM, Glycemic control, Poor, Good, Adequate, Inadequate, Factors, Association, and Determinants. All original articles written in the English language with full-text available and the value of glycemic control defined were included. A total of 1866 studies were retrieved. After the title, abstract, screening, and full-text screening, 12 studies were eligible.The prevalence of poor glycemic control was high, and it ranged between 45.2% and 93% among the studies. The factors associated with glycemic control were stratified into four categories: personal or body-related, clinical, medication-related, and behavioral factors. There was a high prevalence of poor glycemic control in all included studies. The glycemic control was associated with various factors; some were related to the patient or medical conditions while others were related to the behavior of the patients or the medication administrated.

Promotion of biological H2 (Bio-H2) production by the nitrogen-fixing anaerobic microbial consortia using humin, a solid-phase humic substance

Dark fermentative biological hydrogen (Bio-H2) production is expected to be a clean and sustainable H2 production technology, and the technologies have been studied to increase in the product yield as index. This study achieved high product yields of Bio-H2 using nitrogen-fixing consortia under nitrogen-deficient conditions with glucose or mannitol as substrate and humin as the extracellular electron mediator: 4.12mol-H2/mol-glucose and 3.12mol-H2/mol-mannitol. The high Bio-H2 production was observed under the conditions where both nitrogenase and hydrogenase were active in the presence of humin. Nitrogenase activity was confirmed by acetylene reduction activity and hydrogenase activity by Bio-H2 production under nitrogenase-inhibiting conditions with NH4NO3. [Fe-Fe] hydrogenase detected by a specific PCR and acetate, butyrate, formate, lactate, and pyruvate produced as by-products suggested the involvement of both pyruvate-ferredoxin-oxidoreductase and pyruvate formate lyase pathways in Bio-H2 production. Humin promoted the Bio-H2 production beyond the capacity of the consortium, which had reached saturation with the optimum concentrations of glucose and mannitol. Carbon balance suggested the concurrent H2 consumption by hydrogenotrophic methanogenesis and acetogenesis. Bio-H2 production of the washed and starved consortium with reduced humin under conditions with or without NH4NO3 suggests that humin promoted hydrogenase and nitrogenase activity by donating extracellular electrons. Clostridium and Ruminococcus in the consortia were considered major hydrogen producers. Thus, this study demonstrated the outstanding potential of nitrogen-fixing consortia under nitrogen-deficient conditions with humin as an extracellular electron mediator for dark fermentative Bio-H2 production with high yields.

Glucose and oleic acid mediate cellular alterations in GLP-1-induced insulin-positive differentiating UCBMSCs.

Coordinated effects of glucose and oleic acid on glucagon-like peptide-1 (GLP-1) mediated differentiation of insulin-positive differentiating umbilical cord mesenchymal stromal cells (dUCBMSCs) was studied using a co-culture of NCI-H716 (GLP-1+) and UCBMSCs (insulin+). The addition of 2.5mM glucose increased the proliferation of NCI-H716 cells by 30% and induced transformation of UCBMSCs into insulin-secreting cells in 18days as compared to 22days in control cells. Oleic acid (25μM) showed decrease in cell proliferation, autophagy, and apoptosis in NCI-H716 cells while no effect was observed in dUCBMSCs. Prolonged glucose and oleic acid resulted in apoptosis and cell cycle changes in dUCBMSCs after day 18 while higher concentrations resulted in cell death. Additionally, the expression of FAS and ACC mRNA was observed in NCI-H716 and dUCBMSCs post 24-hr addition of glucose and/or oleic acid. Absorption of oleic acid was high in NCI-H716 compared to dUCBMSCs. Taken together, optimal concentrations of glucose and oleic acid could be a key factor in stimulating intrinsic GLP-1, which in turn stimulates differentiating MSCs in a glucose-dependent manner. PRACTICAL APPLICATIONS: The aim of this article was to study whether differentiating or differentiated MSCs after mobilization or post-transplant would require optimal glucose and oleic acid to naturally stimulate intrinsic GLP-1, or otherwise, the high or long-term overload of glucose or oleic acid could result in inhibition of differentiated cells resulting in failure of insulin secretion.

Sequential optimization of bioprocess nutritional parameters for maximum l-asparaginase production from Pseudomonas aeruginosa BGR1I1

l-Asparaginase enzyme belongs to the amidase group which carries out the deamination of asparagine to ammonia and aspartic acid. It has important applications in the pharmaceutical and food processing industries. Extensive screening of l-asparaginase producing bacteria from the rhizospheric soil was carried out. An efficient l-asparaginase producer was selected and identified by morphological, cultural, biochemical methods together with 16S rRNA sequencing as a Pseudomonas aeruginosa BGR1I1. A sequential optimization of bioprocess nutritional parameters was carried out using Plackett-Burman design (PBD) and response surface methodology (RSM) for maximum production of l-asparaginase from Pseudomonas aeruginosa BGR1I1. Fourteen processing variables were screened out using PBD. Four variables (glucose, asparagine, pH and time) found to be significantly affecting l-asparaginase production were further optimized by the central composite design of RSM. Maximum l-asparaginase enzyme activity (307 IU/mL) was obtained under the optimum concentration of glucose, 0.22% asparagine, 0.71% pH, 7.45 of modified M9 medium and incubation time 63 h which is 2.22-fold higher than in the basal medium.

Antagonistic potential of some phosphate solubilizing fungi against some phyto-pathogenic fungi

BackgroundLittle phosphorus availability in soil is one of the major forces for crop production. Phosphate solubilizing fungi enhance available phosphorus from soils and contribute to achieve the plants phosphorus requirement. Phosphate solubilizing fungi are important component of soil microbiota and play an essential role in the biogeochemical cycling of phosphorus in natural ecosystems.ResultsThe study tested the potential of the isolated phosphate solubilizing fungi to inhibit the growth of Alternaria alternata, Fusarium solani, Geotrichum candidum, Rhizoctonia solani and Sclerotium rolfsii. A total of 137 fungal isolates were isolated and identified from 30 soil samples. Nine isolates solubilized inorganic phosphate (tricalcium phosphate). Eight of these isolates were isolated from the rhizosphere of Alhagi graecorum Boiss., Allium cepa L., Ehrharta calycina Sm., Ludwigia stolonifera (Guill. & Perr.) Raven, Mentha longifolia L., Phragmites communis Trin.,Triticum aestivum L. and Zea mays L., respectively and one isolate was isolated from island's free soil. Purified single spore cultures of these nine isolates were identified to species level by multi loci DNA barcoding using internal transcribed spacer1and 2 (ITS1 and ITS 2) of the rRNA gene cluster, Calmodulin (CaM) and β-tubulin)BenA) gene markers.ConclusionsThe isolated phosphate solubilizing fungi belonged to two genera, Aspergillus and Penicillium. The phosphate solubilization index ranged from 1 to 1.5. Aspergillius japonicus 2 had the highest solubilization index (1.5) and also had the highest inhibition percentage (70%) against Alternaria alternata. This isolate is promising for development of biocontrol agent of Fusarium solani, Geotricum candidium and Alternaria alternata. The highest phosphate solubilization by Aspergillius japonicus 2 was obtained by using sucrose as carbon source and also ammonium chloride and tryptophan as nitrogen source. The highest solubilization percentage was 78.2% at optimum glucose concentration (5%) while the pH value that gave the highest solubilization percentage (90%) was 3. After eight days of incubation of Aspergillius japonicus 2, the solubilization percentage reached its maximum value (80.2%).

Development of the optimal procedure for increasing HbA1c concentration in control materials for external quality assessment

The research aimed to increase certain HbA1c concentrations at medical decision levels for external quality control samples from healthy donor blood. The in vitro study was performed from October 2019 to January 2021 at Quality Control Center for Medical Laboratory at University of Medicine and Pharmacy at Ho Chi Minh City. The study observed on the conditions including the optimal buffer solutions (BAGPM, BPS, Ringer, Saline), temperature (2°C - 8°C, 22°C - 24°C, 37°C), and glucose concentration (100 mM, 305 mM, 500 mM) affecting the HbA1c concentration in vitro to make the external quality control samples fell in normal, prediabetes, and diabetes range. At every condition, the HbA1c concentration was measured by Tina Quant method to look for the optimal procedure to increase HbA1c concentration required of the external quality control protocol. The highest HbA1c concentration (11.57±0.2%) was found in BAGPM solution with 100 mM glucose after 15 days with the baseline HbA1c 5.43±0.13%; the HbA1c level increase dramatically at 37°C in BAGPM 500 mM glucose solution in fifteen days (40.03±1.05%). The appropriate conditions were identified to prepare HbA1c standards for prediabetic and diabetic levels. The standards for HbA1c concentrations were recommended to prepare by incubating RBCs from non-diabetic donor blood in BAGPM solution containing glucose at 37°C for 24 hours. Glucose concentrations should be 100 mM and 500 mM, respectively, for prediabetic level (HbA1c ~ 6.0 ± 0.12%) and diabetic level (HbA1c ~ 9.6 ± 0.17%).

Real-time continuous glucose monitoring in preterm infants (react): An International, open-label, randomised, controlled trial.

Continuous interstitial glucose monitoring (CGM) is used to assess glycaemic status in some adults and older children with diabetes.1, 2 Additionally, CGM has been used in term, preterm and low birthweight newborns to evaluate glucose concentrations during the first days of life,3 to evaluate efficacy of dextrose gel in preventing hypoglycaemia,4 or to detect episodes of low glucose, which would go unrecognised with standard, intermittent blood sampling.3, 4 CGM could potentially decrease the number of invasive capillary samplings.5 In the current study, the efficacy of CGM in maintaining glucose within a specified range was investigated. Overall, the intervention arm spent more time within the target range (94%) compared to the standard group (84%) or a total of 13 more hours. Although not statistically significant, more infants in the intervention group (15% vs. 12%) experienced at least one episode of hypoglycaemia (glucose = 2.2–2.6 mmol/L) with 13% in the intervention group versus 7% in the standard group having at least one episode of severe hypoglycaemia (glucose <2.2 mmol/L), consistent with previous studies showing that hypoglycaemic episodes might go unnoticed if relying solely on intermittent sampling. Alternatively, the different incidence of hypoglycaemia could be explained by higher rate of insulin use in the intervention arm (61%) compared to the standard group (37%) and a post hoc analysis of infants receiving insulin might have clarified this possibility. The intervention group had less continuous episodes longer than one hour with sensor glucose <2.6 mmol/L and less time in the hyperglycaemic range. The use of CGM was safe regarding episodes of infection or discomfort. The protocol's6 recommendation to start or increase the insulin dose when glucose levels reach 8 mmol/L might explain why more infants in the intervention arm received insulin in the first week of life compared with the standard group. The total dose of insulin was similar between groups, raising the possibility that infants in the intervention arm might have received insulin for transient elevated glucose levels. Different glucose thresholds and different durations of elevated levels before starting insulin might change the impact of CGM on insulin exposure. One interesting exploratory finding was a higher incidence of NEC in the standard group, possibly due to more time spent in the hyperglycaemic range. This deserves further investigation. The authors did not mention the proportion of growth restricted (IUGR) or small for gestational age infants. It is worth considering whether IUGR or other subgroups of infants with increased glycaemic variability in the first week of life (infants of diabetic mothers, congenital infections and HIE) would have demonstrated a different efficacy of CGM. This study adds to the mounting evidence that CGM in preterms used to achieve glycaemic control is safe and efficacious. It extends the results from previous smaller studies to a larger, multicentre one. The optimal glucose concentration target range for preterms was not addressed. However, the results show that CGM can be used to improve future studies investigating different target glucose ranges in relationship to short- and long-term outcomes. Dr. Rozance has received a StatStrip Glucose Meter from Nova Biomedical for use in his research laboratory. https://ebneo.org/preterm-continuous-glucose-monitoring

Effect of environmental and nutritional conditions on the formation of single and mixed-species biofilms and their efficiency in cadmium removal

Remediation of contaminated water and wastewater using biosorption methods has attracted significant attention in recent decades due to its efficiency, convenience and minimised environmental effects. Bacterial biosorbents are normally deployed as a non-living powder or suspension. Little is known about the mechanisms or rates of bacterial attachment to surfaces and effect of various conditions on the biofilm development, as well as efficiency of living biofilms in the removal of heavy metals. In the present study, the effect of environmental and nutritional conditions such as pH, temperature, concentrations of phosphate, glucose, amino acid, nitrate, calcium and magnesium, on planktonic and biofilm growth of single and mixed bacterial cultures, were measured. Actinomyces meyeri, Bacillus cereus, Escherichia coli, Pseudomonas fluorescens strains were evaluated to determine the optimum biofilm growth conditions. The Cd(II) biosorption efficiencies of the mixed-species biofilm developed in the optimum growth condition, were investigated and modelled using Langmuir, Freundlich and Dubnin Radushkevich models. The biofilm quantification techniques revealed that the optimum concentration of phosphate, glucose, amino acid, nitrate, calcium and magnesium for the biofilm development were 25, 10, 1, 1.5, 5 and 0.5 g L−1, respectively. Further increases in the nutrient concentrations resulted in less biofilm growth. The optimum pH for the biofilm growth was 7 and alkaline or acidic conditions caused significant negative effects on the bacterial attachment and development. The optimum temperatures for the bacterial attachment to the surface were between 25 and 35 °C. The maximum Cd(II) biosorption efficiency (99%) and capacity (18.19 mg g−1) of the mixed-species biofilm, occurred on day 35 (Ci = 0.1 mg L−1) and 1 (Ci = 20 mg L−1) of biofilm growth, respectively. Modelling of the biosorption data revealed that Cd(II) removal by the living biofilm was a physical process by a monolayer of biofilm. The results of present study suggested that environmental and nutritional conditions had a significant effect on bacterial biofilm formation and its efficiency in Cd(II) removal.

Biorefinery system for production of thermostable exopolysaccharide by a novel thermophile Brevibacillus borstelensis MK878423 and its study on impact of glucose utilization

Microbial exopolysaccharides, especially from thermophiles, are gaining attention due to their thermostability and reduced viscosity at elevated temperatures which make them suitable candidates for pharmaceutical, cosmetics and food industries. This study aims to identify potential of a novel thermophile for the production of high amounts of exopolysaccharide. It also reports suitable process parameters for growth of novel thermophile in exopolysaccharide production medium and determination of optimum glucose concentration as its production generally requires high amount of glucose making the process cost intensive. Thermophilic bacteria, from a local hot spring, were screened for the production of exopolysaccharide, and growth kinetics of the best producer, Brevibacillus borstelensis MK878423, was studied. The growth study of bacterium revealed optimum time of production as 40 h, and maximum product was formed at 30 g/l glucose. The logistic growth curve of the bacterium was analysed, and kinetic rate constants for substrate utilization were estimated by modified Luedeking-Piret kinetic model. The specific growth rate of the bacterium was calculated to be 0.0166 h−1 with kinetic rate constants as − 18.953 (α) and 90.655 (β) for Luedeking-Piret substrate. This is the first report on the production of exopolysaccharide by a strain of Brevibacillus borstelensis. Understanding the kinetic rate constants for substrate consumption will help in extrapolating the system of microbial exopolysaccharide production from agricultural wastes with high glucose content. The determination of optimal glucose concentration will also help in utilizing biowastes as substrates for exopolysaccharide production following biorefinery concept as wastes are utilized for the production of value-added chemicals.

Combination of Cell Growth Dependent and Independent Modes for Efficient L-Lactic Acid Production by Lactobacillus paracasei

In this study,on the basis of L-lactic acid production by Lactobacillus paracasei,a high cell density strategy with the combination of cell growth dependent and independent modes was developed through investigating the optimal initial glucose concentration and the metabolic capacity of resting cells. The results indicated that the cells grew well under 140 g/L of initial glucose concentration,and all the glucose could be rapidly exhausted to produce L-lactic acid. Moreover,the cells could still maintain high metabolic activity within 6~7 h after the end of fermentation. Finally,based on the above results,the L-lactic acid productivity of high cell density phase was enhanced by 1.4-fold compared with that of normal batch fermentation,and the L-lactic acid yield was also improved significantly to 0.985 g/g. This study extended the highly efficient production period so as to improve the production efficiency of L-lactic acid. Otherwise,the auxiliary time required in the fermentation process could be effectively reduced,including seed preparation and cell growth. Thus,it would be potentially applied for future industrial lactic acid production.