Optimization of antioxidant activity by response surface methodology in hydrolysates of jellyfish (Rhopilema esculentum) umbrella collagen

To optimize the hydrolysis conditions to prepare hydrolysates of jellyfish umbrella collagen with the highest hydroxyl radical scavenging activity, collagen extracted from jellyfish umbrella was hydrolyzed with trypsin, and response surface methodology (RSM) was applied. The optimum conditions obtained from experiments were pH 7.75, temperature (7) 48.77 ℃, and enzyme-to-substrate ratio ([E]/[S]) 3.50%. The analysis of variance in RSM showed that pH and [E]/[S] were important factors that significantly affected the process (P<0.05 and P<0.01, respectively). The hydrolysates of jellyfish umbrella collagen were fractionated by high performance liquid chromatography (HPLC), and three fractions (HF-1>3000 Da, 1000 Da相似文献   

Optimization of angiotensin I-converting enzyme （ACE） inhibition by rice dregs hydrolysates using response surface methodology

INTRODUCTION Angiotensin I-converting enzyme (ACE) canconvert angiotensin I to angiotensin II which isknown to be a strong vasopressor, besides inactivat-ing bradykinin conducive to lowering blood pressure(Ondetti et al., 1977). This enzyme also playsphysiological roles in the regulation of local levels ofother endogenous peptides, such as enkephalins andsubstace P. Therefore, inhibition of ACE can reducethe activity of angiotensin II, but increase bradykininand enkephalins levels, …     

Optimization of succinic acid fermentation with Actinobacillus succinogenes by response surface methodology (RSM)

Succinic acid is considered as an important platform chemical. Succinic acid fermentation with Actinobacillus succinogenes strain BE-1 was optimized by central composite design (CCD) using a response surface methodology (RSM). The optimized production of succinic acid was predicted and the interactive effects between glucose, yeast extract, and magnesium carbonate were investigated. As a result, a model for predicting the concentration of succinic acid production was developed. The accuracy of the model was confirmed by the analysis of variance (ANOVA), and the validity was further proved by verification experiments showing that percentage errors between actual and predicted values varied from 3.02% to 6.38%. In addition, it was observed that the interactive effect between yeast extract and magnesium carbonate was statistically significant. In conclusion, RSM is an effective and useful method for optimizing the medium components and investigating the interactive effects, and can provide valuable information for succinic acid scale-up fermentation using A. succinogenes strain BE-1.     

Effects of roller burnishing process parameters on surface roughness of A356/5%SIC composite using response surface methodology

In this study, a simple roller burnishing tool was made to operate burnishing processes on A356/5%SIC metal matrix composite fabricated by electromagnetic stir casting under different parameters. The effects of burnishing speed, burnishing force and number of burnishing passes on the surface roughness and tribological properties were measured. Scanning electron microscopy （SEM） graphs of the machined surface with PCD （insert-10） tool and roller burnished surface with tungsten carbide （WC） roller were taken into consider- ation to observe the surface finish of metal matrix composites. The mechanical properties （tensile strength, hardness, duc- tility） of A356/5%SIC metal matrix composites were studied for both unburnished samples and burnished samples. The results revealed that the roller burnished samples of A356/ 5%SIC led to the improvement in tensile strength, hardness and ductility. In order to find out the effects of roller bur- nishing process parameters on the surface roughness of A356/ 5%SIC metal matrix composite, response surface methodol- ogy （RSM） （Box-Behnken design） was used and a prediction model was developed relevant to average surface roughness using experimental data. In the range of process parameters, the result shows that roller burnishing speed increases, and surface roughness decreases, but on the other hand roller burnishing force and number of passes increase, and surface roughness increases. Optimum values of burnishing speed （1.5 m/s）, burnishing force （50 N） and number of passes （2） during roller burnishing of A356/5%SIC metal matrix com- posite to minimize the surface roughness （predicted 1.232 μm） have been found out. There was only 5.03% error in the experimental and modeled results of surface roughness.     

Improvement of xylanase production by Aspergillus niger XY-1 using response surface methodology for optimizing the medium composition

Objective: To study the optimal medium composition for xylanase production by Aspergillus niger XY-1 in solid-state fermentation (SSF). Methods: Statistical methodology including the Plackett-Burman design (PBD) and the central composite design (CCD) was employed to investigate the individual crucial component of the medium that significantly affected the enzyme yield. Results: Firstly, NaNO3, yeast extract, urea, Na2CO3, MgSO4, peptone and (NH4)2SO4 were screened as the significant factors positively affecting the xylanase production by PBD. Secondly, by valuating the nitrogen sources effect, urea was proved to be the most effective and economic nitrogen source for xylanase production and used for further optimization.Finally, the CCD and response surface methodology (RSM) were applied to determine the optimal concentration of each sig-nificant variable, which included urea, Na2CO3 and MgSO4. Subsequently a second-order polynomial was determined by mul-tiple regression analysis. The optimum values of the critical components for maximum xylanase production were obtained as follows: x1 (urea)=0.163 (41.63 g/L), x2 (Na2CO3)=-1.68 (2.64 g/L), x3 (MGSO4)=1.338 (10.68 g/L) and the predicted xylanase value was 14374.6 U/g dry substrate. Using the optimized condition, xylanase production by Aspergillus niger XY-1 after 48 h fermentation reached 14637 U/g dry substrate with wheat bran in the shake flask. Conclusion: By using PBD and CCD, we obtained the optimal composition for xylanase production by Aspergillus niger XY-1 in SSF, and the results of no additional expensive medium and shortened fermentation time for higher xylanase production show the potential for industrial utilization.     

Enhanced production of elastase by Bacillus licheniformis ZJUEL31410： optimization of cultivation conditions using response surface methodology

Sequential methodology based on the application of three types of experimental designs was used to optimize the fermentation conditions for elastase production from mutant strain ZJUEL31410 of Bacillus licheniformis in shaking flask cul- tures. The optimal cultivation conditions stimulating the maximal elastase production consist of 220 r/min shaking speed, 25 h fermentation time, 5% (v/v) inoculums volume, 25 ml medium volume in 250 ml Erlenmeyer flask and 18 h seed age. Under the optimized conditions, the predicted maximal elastase activity was 495 U/ml. The application of response surface methodology resulted in a significant enhancement in elastase production. The effects of other factors such as elastin and the growth factor (corn steep flour) on elastase production and cell growth were also investigated in the current study. The elastin had no significant effect on enzyme-improved production. It is still not clear whether the elastin plays a role as a nitrogen source or not. Corn steep flour was verified to be the best and required factor for elastase production and cell growth by Bacillus licheniformis ZJUEL31410.     

Optimization of extraction of phenolics from leaves of Ficus virens

In this research, the conditions for extraction of phenolics from leaves of Ficus virens were optimized using response surface methodology (RSM). The extraction abilities of phenolics (EAP) and flavonoids (EAF), the 2,2-diphenyl-1-pierylhydrazyl (DPPH) free-radical scavenging potential, and the ferric reducing/antioxidant power (FRAP) were used as quality indicators. The results of single-factor experiments showed that temperature, ethanol concentration, extraction time, and the number of extraction cycles were the main influencing variables, and these provided key information for the central composite design. The results of RSM fitted well to a second degree polynomial model and more than 98% of the variability was explained. The ideal extraction conditions for EAP, EAF, DPPH free-radical scavenging potential, and FRAP were obtained. Considering the four quality indicators overall, the ideal extraction conditions were 58% ethanol at 57 °C for 37 min with three extraction cycles. At the ideal extraction conditions, the values of EAP, EAF, DPPH free-radical scavenging potential, and FRAP were 5.72%, 3.09%, 58.88 mg ascorbic acid equivalent (AAE)/g dry weight (DW), and 15.86 mg AAE/g DW, respectively. In addition, linear correlations were observed between EAP, EAF, and antioxidant potential.     

Application of response surface methodology in medium optimization for pyruvic acid production of <Emphasis Type="Italic">Torulopsis glabrata</Emphasis> TP19 in batch fermentation

Response surface methodology （RSM） was used to optimize the fermentation medium for enhancing pyruvic acid production by Torulopsis glabrata TP19. In the first step of optimization, with Plackett-Burman design, ammonium sulfate, glucose and nicotinic acid were found to be the important factors affecting pyruvic acid production significantly. In the second step, a 23 full factorial central composite design and RSM were applied to determine the optimal concentration of each significant variable. A second-order polynomial was determined by the multiple regression analysis of the experimental data. The optimum values for the critical components were obtained as follows： ammonium sulfate 0.7498 （10.75 g/L）, glucose 0.9383 （109.38 g/L） and nicotinic acid 0.3633 （7.86 mg/L） with a predicted value of maximum pyruvic acid production of 42.2 g/L. Under the optimal conditions, the practical pyruvic acid production was 42.4 g/L. The determination coefficient （R^2） was 0.9483, which ensures adequate credibility of the model. By scaling up fermentation from flask to jar fermentor, we obtained promising results.     

Medium optimization for enhanced production of cytosine-substituted mildiomycin analogue （MIL-C） by Streptoverticillium rimofaciens ZJU 5119

Cytosine-substituted mildiomycin analogue (MIL-C) was produced effectively by supplementing cytosine into the culture of Streptoverticillium rimofaciens. In order to improve the yield of MIL-C, statistically-based experimental designs were applied to optimize the fermentation medium for S. rimofaciens ZJU 5119. Fifteen culture conditions were examined for their significances on MIL-C production using Plackett-Burrnan design. The Plackett-Burman design and one-variable-at-a-time design indicated that glucose and rice meal as the complex carbon sources, and peanut cake meal and NH4NO3 as the complex nitrogen sources were beneficial for MIL-C production in S. rimofaciens ZJU 5119. The results of further central composition design (CCD)showed that the optimal concentration of glucose, rice meal and peanut cake meal were 18.7 g/L, 64.8 g/L and 65.1 g/L,respectively. By using this optimal fermentation medium, the MIL-C concentration was increased up to 1336.5 mg/L, an approximate 3.8-fold improvement over the previous concentration (350.0 mg/L) with un-optimized medium. This work will be very helpful to the large-scale production of MIL-C in the future.     

Antioxidant activity and protective effect of Clitoria ternatea flower extract on testicular damage induced by ketoconazole in rats

Background

Ketoconazole (KET), an antifungal drug, has adverse effects on the male reproductive system. Pre-treatments with antioxidant plant against testicular damage induced by KET are required. The flowers of Clitoria ternatea (CT) are proven to have hepatoprotective potential. However, the protective effect on KET-induced testicular damage has not been reported.

Objective

To investigate the protective effect of CT flower extracts with antioxidant activity on male reproductive parameters including sperm concentration, serum testosterone level, histopathology of the testis, and testicular tyrosine phosphorylation levels in rats induced with KET.

Methods

The antioxidant activity of CT flower extracts was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) assays. Male rats were treated with CT flower extracts (10, 50, or 100 mg/kg BW) or distilled water via a gastric tube for 28 d (preventive period: Days 1–21) and induced by KET (100 mg/kg BW) via intraperitoneal injection for 7 d (induction period: Days 22–28). After the experiment, all animals were examined for the weights of the testis, epididymis plus vas deferens and seminal vesicle, serum testosterone levels, sperm concentration, histological structures and diameter of testis, and testicular tyrosine phosphorylation levels by immunoblotting.

Results

The CT flower extracts had capabilities for DPPH scavenging and high reducing power. At 100 mg/kg BW, the extract had no toxic effects on the male reproductive system. Significantly, in CT+KET groups, CT flower extracts (50 and 100 mg/kg BW) alleviated the reduction of reproductive organ weight parameters, testosterone levels, and sperm concentration. In addition, CT flower extracts gave protection from testicular damage in KET-induced rats. Moreover, in the CT100+KET group, CT flower extracts significantly enhanced the expression of a testicular 50-kDa tyrosine phosphorylated protein compared with that of other groups.

Conclusions

C. ternatea flower extracts possessing antioxidant activity are not harmful to the male reproductive system and can protect against testicular damage in KET-induced rats.