Bioconversion of Shrimp Processing Wastes to Antioxidant Exopolysaccharides by Cantharelluscibarius

GAO Xiu-jun,YAN Pei-sheng,LIU Xin,BAO Zheng,ZHU Yan-ping

School of Marine Science and Technology,Harbin Institute of Technology at Weihai,Shandong Weihai 264209,China

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Bioconversion of Shrimp Processing Wastes to Antioxidant Exopolysaccharides byCantharelluscibarius

GAO Xiu-jun,YAN Pei-sheng*,LIU Xin,BAO Zheng,ZHU Yan-ping

SchoolofMarineScienceandTechnology,HarbinInstituteofTechnologyatWeihai,ShandongWeihai264209,China

Shrimp processing waste was converted and deodorized for production of antioxidant polysaccharides byCantharelluscibariususing response surface methodology.The optimal conditions for highest mycelium biomass and exopolysaccharides production were determined as follows: the solid to liquid ratio was 9.016%,volume of liquid medium was 120.292 mL,and 1.208% concentration of glacial acetic acid.Under the optimal conditions,mycelium biomass and exopolysaccharides production reached 28.407±0.842 g/L and 7.009±0.517 g/L,respectively in validation test,which were consistent with the predicted values (RSD <5%).These values were improved by 60.564% and 114.737%,respectively compared to the initial culture conditions.The scores of deodorization were 3.056±0.115 and 3.694±0.076 at based and optimized validation bioconversion.The resulting exopolysaccharides had high antioxidant activities with total antioxidant capacity of 1.952±0.041 U/mg，superoxide anion scavenging capacity of 93.223±1.174 U/g and hydroxyl radical scavenging capacity of 60.291±0.638 U/mg.The study provided an alternative method for production of antioxidant polysaccharides from shrimp processing waste byCantharelluscibarius.

shrimp processing wastes; bioconversion; deodorization;Cantharelluscibarius; antioxidant exo-polysaccharides

Introduction

Recycling foods processing wastes with biotech-nology has been increasingly concerned.Shrimp is a popular type of seafood,and its production has increased year by year in the last 2 decades.During shrimp processing,the head,shell,tail portion and small fry with low edible value,which makes up approximately 80% weight of the raw materials,are removed and discarded as waste[1].Shrimp processing waste (SPW) contains large amounts of nutritive components,mineral calcium and phosphorus[2].However,uncontrolled discarding and dumping of SPW in coastal can cause natural resources wasting and eutrophication of the marine environment[3].Therefore,attention has been increasingly paid to large-scale recycling of SPW,which has been reused for fertilizer,feedstuff[4～6],and recove-ring nutrients comprise and bioactive substances[7,8].However,methods mentioned above were used only a small part of the waste resource,and had limitation of products with low added value,or causing secondary pollution of environment and increasing the cost due to a large quantity of strong acid or base need to be used in reutilization[9].Moreover,fishy odor and extracts of SPW is the key limiting factor of reutilization.It was found in this study that SPW can be converted and deodorized byCantharelluscibariusin submerged fermentation.

Mushrooms has gotten a lot of scientific interest,because of their potential value of nutrition and medicine,and it is rich in bioactive components.Polysaccharides are important group of bioactive substances due to their various bioactivities,such as antioxidant,immuno-enhancing,hypolipidemic or antitumor properties[10～15].Cantharelluscibariusbelongs to the family of Cantharellaceae and the genus ofCantharellus.Fruiting bodies ofC.cibariusis rich in bioactive substances,such as phenolic compounds[16,17],homodimeric laccase[18],polysaccharide[19,20]and acetylenic acid[21]etal.,and their properties of antitumor[22],anti-inflammation[23,24],antivirus[18],antioxidation[17,24]and effects on the gene expression[21].However,traditional methods to culture fruiting bodies of mushrooms usually take 4～6 months.Furthermore,many fruiting bodies are difficult to be cultured artificially.These have limited the application of using mushrooms as drugs or functional foods in large,industrial scale,due to their low production and high cost.In general,culturing mycelia in liquid medium by submerged fermentation is a very rapid and cheap method to obtain fugal biomass and their bioactive components without occupation of land and pollution environment.However,there is no report about bioactivities of products from liquid submerged fermentation ofC.cibarius.

It is well known that the antioxidant compounds plays an important role in inhibiting or preventing oxidation of a substrate,and evolving to protect biological systems against damages.In the process of searching for effective,natural antioxidants,mushrooms are increasingly being considered as a rich source,and some polysaccharide extracts from liquid fermented products of edible fungi were proved to have free radical scavenging activities[25,26].Moreover,mycelium biomass and polysaccharide production in liquid fermentation was strongly influenced by culture medium and conditions[27,28].

Therefore,reusing SPW as a cheap medium ofC.cibariusfor submerged fermentation for mycelium biomass and antioxidant exopolysaccharides (EPS) could not only reduce cost and gain high-value-added products,but also recover the waste resources and protect the environment.Furthermore,it may obtain the foundational scientific data of reusing SPW in large scale as well as producing mycelia and antioxidant EPS fromC.cibarius.In this paper,cultural conditions ofC.cibariusgrown in liquid medium consist of SPW were optimized through Plackett-burman,path of steepest ascent and Box-behnken design in sequence.The goal of this study was to find out the optimum conditions of bioconversion of SPW byC.cibarius,and then afford foundation for recycling SPW in industrial scale and low-cost production of mycelium biomass and antioxidant polysac-charides fromC.cibarius.

1 Materials and Methods

1.1 Materials

SPW (purchased from a local shrimp processing plant) dried at 50℃ and pulverized to powder.The total antioxidant,anti-superoxide anion radical and anti-hydroxyl radical kits were purchased from Nanjing Jiancheng Bioengineering Research Institute in China.

1.2 Methods

1.2.1FungalstainandbioconversionofSPWC.cibariusmaintained on pitched potato dextrose agar (PDA) medium at 4℃ in our laboratory was activated in Petri dishes on the solid medium (PDA) at 25℃ for 10 days.Then,mycelia ofC.cibariuson the utmost edge were cut into pieces (about 0.5 cm in diameter) and ten pieces of them were transferred to the culture flasks containing 100 mL of liquid PDA medium.The fermented product served as liquid seeds for bioconversion and control for determining the mycelium biomass and content of polysaccharides of the converted product.The liquid SPW medium for elementary bioconversion was composed of 7.00 g solid power (containing 95% of SPW and 5% of bran powder) and 100 mL distilled water with 1.3% acetic acid.The liquid media for optimization were prepared on different solid to liquid radio,concentration of acetic acid and content of bran powder to meet the demand of experimental design (Table 1).All bioconver-sions were carried out in a 250 mL flask which contained 100 mL medium and 5% of inoculums concentration in elementary bioconversion and different column of medium and inoculums concentration in optimization procedure to meet the demand of experimental design.The flasks were inoculated on a rotary shaker at 120 r/min and 25℃ in elementary bioconversion and different rotation rate and temperature in optimization procedure to meet the demand of experimental design.

1.2.2DeodorizationeffectofthebioconversionAfter bioconversion,the fishy odor of converted products and the control blank SPW medium were assessed using sensory evaluation.In the assay,subjects in a consumer panel (n=12,ages 18～25,evenly divided between male and female) were asked to choose one portion from a total 5 options,including extremely strong,comparably strong,a little,slight fish and no fishy smell,noted as 0～4 points,after smelling each sample.A sample with a heavier fishy odor received a lower the score.The blank control mediums were evaluated and scored at the same time as the converted products.

1.2.3DeterminationofmyceliumbiomassandyieldofcrudeEPSfromconvertedproductsThe converted products and their corresponding control were divided into solid constituent and filtrates by filtering through gauze.Then,the solid constituents were washed with deionized water for 3 times,and then lyophilized and weighted.The biomass of mycelium was calculated by subtracting the weight of solid constituents of control from the total weight of solid bioconversion product.The fermented supernatants were filtered with filter paper,and added with 4 volumes of absolute ethanol.The raw EPS subsided at 4℃ for 12 hours,and centrifuged at 5 000 r/min for 20 min.Then,precipitates were collected,washed with 95% ethanol twice,lyophilized,and weighed.After that,10 mg of the EPS was dissolved with distilled water at 60℃ and determined the content of EPS (the phenol-sulfuric acid method,where glucose was used as a standard).The yield of EPS was defined as product of the weight of crude EPS and EPS content.

1.2.4Optimizationofconditionsofbioconversion

①Plackett-burman (PB) design.There were 8 variables,denotedX1～X8,were screened in PB design to examine the variables that have significant influence on the responses in bioconversion.All experimental trials,factors and their levels are shown in Table 1.There were a high (+1) and low (-1) level being assigned for each independent variable.The low (-1) ones were the same as those in the elementary bioconversion.The response values were mycelium biomass and EPS production.Based on the results gained from the PB design,the first-order model was as follow:

Y(1,2)=β0+∑βiXi(i=1…k)

(1)

WhereY1andY2refer to the mycelium biomass and EPS production; β0to the constant;βito the regression coefficients; andXito the coded independent factors showed in Table 1.

②Path of steepest ascent.The first-order regression models of the mycelium biomass and EPS production in terms of coded factors were built based on these results,which were as equation (2) and (3):

Y1=10.230+5.435X1-0.745X2+2.770X3

+1.073X4-0.748X5-5.589X6+0.848X7-0.733X8

(2)

Y2=2.608+1.230X1-0.015X2+0.317X3

+0.254X4-0.304X5-0.923X6+0.077X7-0.030X8

(3)

WhereY1refers to the mycelium biomass,Y2to the yield of the EPS,andX1～X8are the coded factors.

According to results of the PB design,3 key variables were chosen for steepest ascent experiment,which was preceded by the key factors moving sequentially along the path of steepest ascent or descent towards an optimal region.The starting point of the steepest ascent path was the center of the PB design,and step-size was assigned based on process knowledge and other practical considerations.The direction of that was the direction in which the response values increased the most.

③Response surface methodology (RSM).RSM (Box-behnken design,BBD) has been frequently applied for explaining the combined effects of the key factors and their interactions,and providing a precise description about the relationship between the factors and the resulting response values.Results of the BBD were expressed by the following second-order polynomial equation(4).

Table 1 Plackett-burman experimental design matrix for screening the culture conditions with mycelium biomass and yield of crude EPS as response.

(4)

WhereY1refers to mycelium biomass,Y2to the EPS production,β0to the offset term,βito the linear effects,βiito the squared terms,βijto the interaction effects,andXiandXjto the coded independent factors.

Three variables (X1,X3andX6) were used to determine the optimum values by RSMviaBBD.

The results of the BBD were fit with the following second-order (equation 4 and 5) model in terms of coded factors:

Y1=28.719+1.211X1-0.558X3-2.173X6+1.029X1X3-1.025X1X6-1.622X3X6-5.768X12-4.762X32-11.112X62

(5)

Y2=7.086-0.248X1+0.261X3+0.859X6+0.409X1X3+0.751X1X6-0.030X3X6-0.647X12-1.135X32-2.152X62

(6)

WhereY1,Y2,X1,X3andX6were the same variables presented in equation 2 and 3.

④Verification of the model.The adequacy of RSM model was experimentally examined at optimal conditions in order to obtain a maximum mycelium biomass and EPS production.Therefore,results obtained in the based bioconversion stage and the predicted values were compared to the results of vivificated experiment to validate the model.

1.2.5AntioxidantactivitiesexaminationAntioxidant activities of all EPSs were detected by assays of total antioxidant (T-AO),anti-superoxide anion radical (ASAR),and anti-hydroxyl radical (AHR) activities.All experiments were carried out according to the specifications of the kits.The T-AO activity assay was used for measuring the ferric-reducing power of the samples.The absorbance was examined at 550 nm against distilled water.The T-AO and AHR capacity of vitamin C was examined at the same time for a positive control.The T-AO,ASAR and AHR activities were calculated according to the equation (7),(8) and (9):

T-AO activity(U/mg)=[(ODE-ODC)×N]/(0.01×30×C)

(7)

ASAR activity (U/g)=[(ODC-ODE)×CS×1 000 mL]/[(ODC-ODS)×C]

(8)

AHR activity (U/mg)=[(ODC-ODE)×8.824]/[(ODC-ODB)×C×V]

(9)

Where ODErefers to the optical density of the experiment group,ODCto the control group,ODs to the standard solution,and ODBto the blanking sample; 8.824 to the molar concentration of H2O2(0.03%);Cto the concentration of the samples (mg/mL or g/L);CSto the concentration of a standard solution (vitamin C,0.15 mg/mL);Nto the dilution of the reaction system; andVto the volume of the samples.

A unit of T-AO activity was defined as the amount of the absorbance being increased by 1 mg of a certain sample at 37℃ for 1 min by 0.01.A unit of ASAR capacity was defined as the amount of superoxide anion reduced by 1 g of a certain sample,which was equal to the effect 1 mg of vitamin C hid,at 37℃ for 40 min.A unit of AHRA refers to 1 mg of sample made H2O2by 1 mmol/L reduce in the reaction system at 37℃ for 1 min.

1.3 Statistical analysis

All experiments were executed in triplicate.Results of based bioconversion stage,the steepest ascent,and verification experiments were analyzed statistically by using analysis oft-test and variance (ANOVA) with SPSS 16.0 software.The P-B and RSM experimental design were designed and analyzed with the design expert 7.1.6 software.

2 Results and Discussion

2.1 Deodorization effect

Mycelium biomass and EPS production of based bioconversion SPW was converted byC.cibariusthrough submerged fermentation for 10 days.Results showed that the SPW medium was fit for fungal species growth and swarming with mycelia (Fig.1,Color figure in inside back cover).

Fig.1 Mycelia growing in liquid SPW medium.

The deodorization score of the blank SPW medium (0.433±0.017) was significantly lower than that of SPW converted byC.cibarius(3.056±0.115,P=0.000),where a score of 3 represents a slight fishy odor.Results also indicated that the mycelia biomass was determined as 17.962±0.988 g/L,and EPS production as 3.264±0.157 g/L.

2.2 Bioconversion conditions optimization for mycelium biomass and EPS production

2.2.1PBdesignforscreeningoffermentationconditionsThere are 12 experimental trials in elementary bioconversion in PB design.The mycelium biomass ofC.cibariusgrown in liquid SPW medium ranged from 0.716±0.041 g/L to 26.101±0.904 g/L and EPS production from 0.603±0.031 g/L to 5.722±0.149 g/L (Table 2).

Table 2 Mycelium biomass and EPS production in different treatments of culture conditions.

Note:Treatments are the same as Table 1.

The pareto plot (Fig.2) demonstrated the signifi-cance of independent variables affecting the mycelium biomass and EPS production,which wereX6>X1>X3>X4>X7>X5>X2>X8andX1>X6>X3>X5>X4>X7>X8>X2,respectively.Furthermore,results of ANOVA analysis of regression models (Table 3) implied that 3 independent variables (X6,X1,X3) had a significant effect on the mycelium biomass and 4 (X1,X6,X3,X5) on the EPS production (P<0.05).The determination coefficient (R2) of regression the model for mycelium biomass (0.985 1) meant that 98.51% of the variability of the response could be predicted by the model.TheF-value of 24.722 implied the model was significant (P=0.011 7).The PredR2of 0.760 9 was in reasonable agreement with AdjR2of 0.945 2.TheR2value of the regression model for the EPS production (0.992 1) meant that 99.21% of the variability of the response could be predicted by the model.TheF-value of 47.312 implied the model was significant (P=0.004 5).The PredR2of 0.874 2 was in reasonable agreement with AdjR2of 0.971 2.

Fig.2 Pareto plot for Plackett-burman parameter estimates for 8 factors.

According to the results of PB design,there were 3 significant variables (X6,concentration of glacial acetic acid;X1,solid to liquid ratio;X3,volume of liquid medium) in the models were considered the major factors for further optimization.Other factors were excluded from the following optimization because of significant smaller contributions to the models.In some reports,independent variables with confidence levels above 80% or 85%[27,29]were chosen for further optimization and 3 ～5 significant independent variables were chosen as major factors for further optimization[30].In the present study,the top 3 independent variables were chosen for further optimization,with confidence levels of 76.888% for mycelium biomass and 78.391% for EPS production.

The high (+1) level ofX4(inoculation amount of mycelium) andX7(cultural temperature) were chosen in all trials,due to their positive regression coefficients in the 2 models.Whereas,X2(content of bran powder),X5(rotation rate) andX8(cultivation time) were used at a low (-1) level,because of their negative regression coefficient in the 2 models.

Table 3 ANOVA analysis for the Plackett-burman factorial model of mycelium biomass and EPS production.

2.2.2PathofthesteepestascentforneighborhoodofoptimumresponseThe path of the steepest ascent experiments was carried out in accordance with the sited factors and their levels.The results (Table 4) indicated that the optimal neighborhood of the mycelium biomass were 28.094±0.517 g/L when the solid to liquid ratio was 9.00%,the volume of liquid medium was 125 mL,and the concentration of glacial acetic acid was 1.10%.The EPS production were 6.980±0.322 g/L when the solid to liquid ratio was 8.50%,the volume of liquid medium was 120mL,and the concentration of glacial acetic acid was 1.20%.The levels of these 3 factors used in BBD were set up as Table 5 when both the mycelium biomass and yield and of EPS were taken into consideration.

2.2.3Box-behkendesign(BBD)forfurtheroptimizationThe levels of the 3 factors,design matrix and corresponding responses of the BBD experiments were shown in Table 5.It was implied that variation in the mycelium biomass and yields of EPS depended upon the culture conditions considered.The effect of a single factor,interaction between the 2 factors,and the quadratic effect were represented in the coefficients with one factor,2 factors,and those with second-order terms,respectively.Results of the regression and ANOVA analyses on the models of the BBD (Table 6) indicated that theF-value of the models (66.597 and 37.661) meant the models were significant (P<0.000 1).TheR2value for the 2 regression models were 0.988 5 and 0.979 8,respectively,which meant that 98.85% of the mycelium biomass variability and 97.98% of EPS production variability were predicted by the models.The PredR2values for the 2 regression equations of 0.872 8 and 0.854 0 were in reasonable agreement with their AdjR2values of 0.973 6 and 0.953 8,respectively,which indicated that there was a high degree of correlation between the experimental and predicted values.ThePvalues of the lack of fit for the 2 regression models (0.195 3 and 0.531 3) were higher than 0.05,making them not significant.This implies that the models describe variability of mycelium biomass and EPS production affected by the factors successfully.

Table 4 Experimental trails in the steepest ascent (descent) path.

Table 5 Box-behnken designs of different factors with their responses.

Table 6 ANOVA analysis for quadratic regression model of the mycelium biomass and EPS production in BBD.

The three-dimensional plots of response surface were constructed to evaluate the effects of the independent variables and their interactions on the mycelium biomass (Fig.3A-C,Color figure in inside back cover) and EPS production (Fig.3D-E).The mycelium biomass rose as the solid to liquid ratio increased from 8.00% to 9.50%,and declined when the solid to liquid ratio ranged was beyond 9.50% (Fig.3A).The effect of volume of liquid medium and concentration of glacial acetic acid on mycelium biomass also varied within the tested range (Fig.3B and C).The highest mycelium biomass ofC.cibariuswas predicted as 28.904 g/L under optimal bioconversion conditions (the solid to liquid ratio of 9.112%,the volume of liquid medium was 119.707 mL and the concentration of glacial acetic acid was 1.180%).In addition,the EPS production increases when the solid to liquid ratio increased up to 9.00%～9.50%,but decreases rapidly beyond this (Fig.3D).The effect of volume of liquid medium and concentration of glacial acetic acid on EPS production also varied within the tested range (Fig.3E-F).The highest EPS production was predicted as 7.188 g/L under the optimum bioconversion conditions (solid to liquid ratio of 8.953%,the volume of liquid medium was 121.044 mL and the concentration of glacial acetic acid was 1.238%).

Finally,the model for both mycelium biomass and EPS production was predicted as the solid to liquid ratio of 9.016%,the volume of liquid medium of 120.292 mL,and the concentration of glacial acetic acid of 1.208%.Under the optimal bioconversion conditions,mycelium biomass and EPS production were predicted as 28.610 g/L and 7.120 g/L.

2.2.4ValidationexperimentsExperiments for validating the models were carried out in triplicate using the optimum bioconversion conditions for the highest mycelium biomass and EPS production.The measured biomass was determined as 28.855±0.956 g/L and improved by 60.645% under the optimal bioconversion conditions for the highest mycelium biomass,which was not significantly different from the predicted yield of 28.904 g/L (P>0.05).The measured EPS production was determined as 7.146±0.321 g/L and improved by 118.934% under the optimal bioconversion conditions for the highest EPS production,which was not significantly different from the predicted biomass of 7.188 g/L(P>0.05).Finally,the measured biomass and EPS production was 28.407±0.842 g/L and 7.009±0.517 g/L,respectively under the optimum bioconversion conditions for both the highest mycelium biomass and EPS production,and were improved by 60.564% and 114.737%.Again these values are not significantly different from the predicted values of the mycelium biomass 28.610 g/L and EPS biomass of 7.120 g/L,respectively (P>0.05 for both).The results implied that SPW was converted byC.cibariuswith high efficiency under the optimized conditions due to their suitablity for high mycelium biomass and EPS production ofC.cibariusgrown in liquid SPW medium.

Fig.3 Response surface plots of the mycelium biomass (A～C) and EPS production (D～E).A,D: Interaction of the solid to liquid ratio and volume of liquid medium; B,E: Interaction of the solid to liquid ratio and the concentration of glacial acetic acid; C,F: Interaction of the volume of liquid medium and the concentration of glacial acetic acid.(Color figure in inside back cover)

The deodorization score of the bioconversion products under the optimal bioconversion conditions for the highest mycelium biomass,EPS production and both of them were determined as 3.778±0.062,3.639±0.064 and 3.694±0.076,respectively,and improved by 23.626%,19.077% and 20.877% compared with the production obtained before optimization.The scores were near to 4,which represented no fishy odor.

2.3 Antioxidant activities of the EPS

The antioxidant activities of crude EPS fromC.cibariusconverted SPW were evaluated with T-AO,ASAR and AHR activity assays.

The T-AO activity of the crude EPS fromC.cibariusconverted SPW was determined as 1.952±0.041,which was far higher than the T-AO activity of polysaccharide from its corresponding blank medium (0.102±0.022 U/mg,P<0.001) and lower than the T-AO activity of vitamin C (20 mmol/L,2.969±0.311 U/mg,P<0.001).The ASAR activity of crude EPS gained after optimization was determined to be 93.223±1.174 U/g,which was higher than that of the polysaccharide value obtained from the blank medium (14.886±0.725 U/g,P<0.0001).Therefore,the ASAR activity indicated that 1g the crude EPS could inhibit the same amount of the superoxide anion as 93.223 mg of vitamin C did.The AHR activity of the crude EPS was determined as 60.291±0.638 U/mg,which was higher than the value obtained from the blank medium (10.965±0.357 U/mg,P<0.001),and was 83.345% of the AHR activity of vitamin C (5 mmol/L,72.339±0.914 U/mg).

3 Discussion

The results indicated that optimizing the bioconversion conditions with PB design,the steepest ascent path,and BBD in sequence was effective and reliable in selecting the statistically significant factors and their optimal levels for the highest mycelium biomass and EPS production fromC.cibariusconverted SPW.The SPW contains large amounts of nutritive components,mineral calcium and phosphorus[2],can be converted and deodorized byC.cibariuseffectively by adding a small amount of carbon source in this paper.Moreover,it has been fermented by lactic acid bacteria[9],Bacilluscereus[31]andExiguobacteriumacetylicum[29]to recover chitosan and chitin.However,about 1% of glacial acetic acid was added to begin bioconversion[9,32]due to the SPW is subalkline.In the present study,1.180% of glacial acetic acid was added to the SPW medium for the highest mycelium biomass when the solid to liquid ratio was 9.112%,which resulted in a pH value of 5.974±0.072.1.238% of glacial acetic acid was added to the SPW medium for the highest EPS production when the solid to liquid ratio was 8.953%,which resulted in a pH value of 5.250±0.093.1.208% of glacial acetic acid was added to the SPW medium for both the highest mycelium biomass and EPS production when the solid to liquid ratio was 9.016%,which resulted in a pH value of 5.517±0.077.The medium pH may affect metabolite formation,product biosynthesis of cells and uptake of various nutrients.It had been reported that EPS production in cultures ofSclerotiumglucanicumandGanodermalucidumwas greatly affected by culture pH,and the optimum pH was 3.5～4.5 over long-term cultivation[33,34]which was much lower than the results in the present study.It has been claimed in other reports that maximum EPS production ofAgrocybecylindraceaobtained in cultures grown at an initial pH 6.0[28],which were a little higher than the results in the present study.However,maximum biomassA.cylindraceaobtained in cultures grown at an initial pH of 4.0[28],which was much lower than the results in the present study.It has also been reported that the optimum pH value of many kinds of mushroom in submerged fermentation high mycelium biomass and EPS production is acidic.

The SPW and its extracts have an unpleasant fishy odor,which is the key limiting factor to its reutilization.Thus,treatment for deodorization has become an important part of its reutilization.Currently,livestock manure can be deodorized with physical,chemical and biological methods.Biological deodorization has increasingly become a hot topic in the study of fishy odor control due to its eliminating the fishy odor permanently at a low cost without the secondary pollution.The stains used for deodorization are always yeast[35].A fungal stain,C.cibarius,was found to be effective in deodorization of SPW in the process of converted the SPW for mycelium biomass and antioxidant EPS,for the first time in this study.It has vast importance to reutilize the wastes with unpleasant odors.

Currently,polysaccharides from medicinal/edible fungi have been increasingly concerned due to their antioxidant power.Determining the T-AO activity is necessary to evaluate the antioxidant activity of bioactive substances for its acting to scavenge various kinds of free radicals,playing a protective bioactive roleinvivo.Additionally,some free radicals,such as the superoxide anion and hydroxyl radical,are considered as high risk factors for many diseases.Therefore,T-AO,AHR and ASAR activities were also measured in this paper.T-AO activity of crude EPS fromHypsizygusmarmoreuscultured in several different kinds of fungal medium were previously determined[36]as 0.813 U/mg.Gaoetal.[32]reported that the T-AOA,ASAR and AHR activity of crude EPS fromB.eduliscultured in SPW was 1.718 U/mg,46.703 U/g and 48.255 U/mg,andS.bovineswere determined to be 1.053 U/mg,25.797 U/g and 52.149 U/mg.In this study,the T-AO,ASAR and AHR activities of EPS fromC.cibariuswere far greater than the antioxidant activities of EPS from fungus in previous reports.

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雞油菌生物轉(zhuǎn)化蝦加工廢棄物生產(chǎn)抗氧化胞外多糖的研究

高秀君, 閆培生*, 劉 欣, 寶 鉦, 朱延平

哈爾濱工業(yè)大學(xué)(威海)海洋科學(xué)與技術(shù)學(xué)院,山東 威海 264209

利用響應(yīng)面法研究了雞油菌轉(zhuǎn)化蝦加工廢棄物脫腥和抗氧化多糖的生產(chǎn)。生產(chǎn)菌絲體和胞外多糖的最優(yōu)發(fā)酵條件為料液比9.016%,裝液量120.292 mL,冰醋酸含量1.208%，驗(yàn)證實(shí)驗(yàn)結(jié)果表明該條件下菌絲體產(chǎn)量為28.407±0.842 g/L，多糖產(chǎn)量為7.009±0.517 g/L，分別較優(yōu)化前提高了 60.564%和114.737%，而且與回歸方程預(yù)測值接近(RSD<5%)。優(yōu)化前去腥效果得分為 3.056±0.115， 優(yōu)化后驗(yàn)證試驗(yàn)中得分為3.694±0.076。優(yōu)化條件下獲得的胞外多糖的總抗氧化能力為1.952±0.041 U/mg，抗超氧陰離子能力為93.223±1.174 U/g，抗羥自由基能力為60.291±0.638 U/mg。研究結(jié)果為利用雞油菌轉(zhuǎn)化蝦加工廢棄物生產(chǎn)抗氧化多糖提供了參考。

蝦加工廢棄物；生物轉(zhuǎn)化；脫腥；雞油菌；抗氧化胞外多糖

2015-04-01; Accepted：2015-05-11

s:Supported by National 863 Program (2008AA10Z327); the Science and Technology Research and Development Plan of Weihai (2010-3-96).

10.3969/j.issn.2095-2341.2015.03.13

Author：GAO Xiu-jun,lecturer,majored in bioconversion of aquatic processing wastes; E-mail: gaoxiujun@hitwh.edu.cn.*Correspondance: YAN Pei-sheng,Professor,majored in marine microorganisms resources and utilization,high value-added utilization of marine organism-derived processing wastes,biocontrol of mycotoxins,and microbial fermentation and biopharmaceuticals.E-mail:yps6@163.com