Ca-alginate Beads Research Articles

A promising laccase immobilization approach for Bisphenol A removal from aqueous solutions

The immobilization of crude laccase from Trametes pubescens by glutaraldehyde crosslinking prior to entrapment into Ca-alginate beads increased the immobilization yield by 30% and reduced the leaking by 7-fold compared to the immobilization with no crosslinking. The performance of the newly developed biocatalyst to degrade Bisphenol A (BPA) from aqueous solutions was tested. Thus, operating at optimal conditions (i.e. pH 5, 30 °C, 20 mg L−1 BPA and 1500 U L−1 laccase), a BPA removal higher than 99% in 2 h was achieved. This value is higher than those reported to date for BPA removal by immobilized laccases. In addition, the biocatalyst was able to remove BPA in 10 successive batches with an efficiency higher than 70% at the end of the last batch. BPA adsorption on the alginate beads was negligible, therefore BPA removal was only due to laccase action. Moreover, Fourier-transform Infrared (FTIR) spectroscopy suggested BPA transformation by laccase.

Production of lactic acid from soybean straw using immobilized Lactobacillus casei and batch or repeated-batch fermentation

Approximately 18 million tons of soybean straw are produced annually in China, with its disposal becoming an increasingly serious problem. Moreover, the Chinese government has banned the open burning of agricultural straw for environmental reasons. One potential solution is to use soybean straw for lactic acid (LA) production, avoiding open burning and waste. In this study, a Ca-alginate-immobilized Lactobacillus casei strain was used to produce LA from soybean straw enzymatic hydrolysate. Optimized conditions for the production of LA were initially established, consisting of Ca-alginate beads made from 2.5% sodium alginate with a diameter of 2 mm and a fermentation process using a 10% inoculum at 30 °C for 30 h. Lactic acid productivity was increased with only a slight decrease in overall yield by raising the initial sugar concentration from 8 g L-1 to 35 g L-1. Finally, immobilized cells could be reused at least 10 times without a noticeable performance decrease. These results indicated that production of LA from soybean straw enzymatic hydrolysate is a sustainable and feasible method to utilize these resources.

The elucidation of surrounding alginate gels on the pollutants degradation by entrapped nanoscale zero-valent iron.

The adsorption capacity of calcium alginate (Ca-alginate) beads was evaluated by measuring the removal of three organic compounds with different charges (malachite green, p-chlophenol and methyl orange). The diffusion was investigated in Ca-alginate hydrogel as a function of solute charge. It was found that an increased electrostatic attraction between the hydrogel and solute would improve the mobility of solute and hence enhance its adsorption efficiency. The degradation kinetics of charged pollutants by Ca-alginate with NZVI entrapped (NZVI-alginate) beads was compared to that of bare NZVI and the data followed a pseudo-first-order kinetic model. Negatively charged Ca-alginate hydrogel strongly adsorbed positively charged pollutant, which led to an enhancement in degradation rate. However, the degradation efficiency of neutral and negatively charged pollutants by NZVI-alginate was comparable with that by bare NZVI. Thus, the degradation ability of NZVI-alginate was related with the diffusion and adsorption behavior of solutes in Ca-alginate hydrogel. The experimental results showed that the free calcium ions containing in Ca-alginate had a significant impact on the adsorption and degradation behaviors of positively charged pollutant, but those of neutral and negatively charged pollutants were only moderately affected. With the dispersity of NZVI particles in beads (1:1-1:4, w/w) increasing, the degradation efficiency of malachite green was improved, whereas further increase of NZVI dispersity (1:6, w/w) brought about a depressed degradation.

Encapsulation of glucose oxidase in alginate hollow beads to reduce the fermentable sugars in simulated musts

The treatment of must with glucose oxidase (GOX) is a biotechnological alternative to the production of reduced-alcohol wines. Nevertheless, the low pH of must is a limiting factor for the enzyme's activity. This study reports on a simple immobilization method that uses enzyme encapsulation to overcome that limiting factor. The encapsulation of GOX was acceptably optimized using response surface methodology (RSM). An immobilization yield of 73% was obtained with 22 g L−1 Na-alginate, 20 g L−1 carboxymethylcellulose, and 12 g L−1 CaCl2. The apparent Km value of the immobilized GOX (4.55 mM) was slightly higher than that of the soluble enzyme (3.99 mM) and the activation energy was similar (~ 35 kJ mol−1). The encapsulated enzyme maintained about 68% and 92% of its initial activity at pH 3.0 and 4.0, respectively. Moreover, GOX-loaded alginate hollow beads could be re-used with 7 reaction cycles in model must, with a final reaction efficacy of 37%. GOX was successfully encapsulated in Ca-alginate hollow beads, and their catalytic potential remained unaffected by the immobilization process. In view of these results and the activity of the immobilized enzyme at the acidic pH of the must, this encapsulated biocatalyst is a promising alternative for industrial use in the production of reduced-alcohol wines.

Calcium Alginate Bead-mediated Enhancement of the Selective Recovery of a Lead Novel Antifungal Bacillomycin Variant

In the pursuit of new antifungal compounds, five coproduced lipopeptide variants (AF1 to AF5) from wild-type Bacillus subtilis RLID 12.1 were identified in our previous study. Out of five, AF4 was identified as a novel lead molecule belonging to the bacillomycin family showing less cytotoxicity at its respective minimum inhibitory concentrations (MIC) evaluated against 81 strains of Candida and Cryptococcus species (including clinical isolates); besides this, AF4 purified in the present study exhibited encouraging MIC values against 10 clinical mycelial fungi. Aiming for a selective production augmentation of AF4 lipopeptide variant, a new fermentation media comprising malt extract (1.01%), dextrose (0.55%), peptone (1.79%), MnSO4 (2mM), and NaCl (0.5%) was formulated. Maximum production of 954.8 ± 10.8mg/L was achieved with 44% selectivity at 30°C compared to unoptimized conditions (186.4 ± 6.1mg/L). Use of calcium alginate beads in the formulated media during the onset of lipopeptide production resulted in an augmentation in the selectivity of the most efficacious AF4 variant to about 72% presumably due to attenuation of other coproduced lipopeptide variants AF1 and AF2. Difference in yield of lipopeptides varied with bead size, bead preparation ratios, and sodium alginate concentrations. Use of Ca-alginate beads in the upstream production process of the lead AF4 variant may be considered as a novel strategy to address the potential challenge that may arise during the scale-up and downstream processing steps. Another significant finding derived from the study is that the proportion of bacillomycin variants of B. subtilis RLID 12.1 could be controlled by temperature and metal ions under static and shaking conditions.

FERMENTATION CHARACTERISTICS OF CAMPBELL EARLY GRAPE WINE INOCULATED WITH INDIGENOUS KOREAN WINE YEASTS ENCAPSULATED IN CA-ALGINATE BEADS AFTER AIR-BLAST DRYING

The aim of this study was to test the possibility of using yeast cells encapsulated in calcium alginate (Ca-alginate) beads as a starter for wine fermentation. Characteristics of Korean Campbell Early wines fermented by five free yeast cell types and those encapsulated in 2% Ca-alginate beads were compared using physicochemical analyses and sensory evaluation tests. The encapsulated yeast cells were shown to ferment Korean Campbell Early grapes with a similar efficiency as that exhibited by the five free yeast cell-types. After fermentation, the characteristics of free cells and encapsulated cells did not show significant differences in terms of content of reducing sugars, soluble solids, total acids, organic acids, and free sugars, as well as in terms of viable cell numbers and other physicochemical properties. The encapsulated cells did, however, produce more alcohol than the free cells. Encapsulation in 2% Ca-alginate beads was furthermore found to decrease the production of negative volatile compounds. The sensory evaluation of wines fermented by free cells compared with those fermented by Ca-alginate bead-encapsulated cells yielded similar scores for the following properties: color, taste, flavor, and overall preference. Overall, no significant differences were observed between the two grape wines, and yeast cells encapsulated in 2% Ca-alginate beads therefore showed high stability and served as an effective yeast starter for wine fermentation.

Degradation of cationic surfactants using immobilized bacteria: Its effect on adsorption to activated sludge

Adsorption of cationic surfactants (QACs) Br-tetradecyltrimethylammonium (TTAB), Cl-tetradecylbenzyldimethylammonium (C14BDMA) and Cl-hexadecylbenzyldimethylammonium (C16BDMA) to activated sludge from a wastewater treatment plant was tested. Adsorption equilibrium was reached after 2 h, and for initial 200 mg L−1 81%, 90% and 98% of TTAB, C14BDMA and C16BDMA were respectively adsorbed. After six successive desorption cycles, 21% of TTAB and 12.7% of C14BDMA were desorbed from the sludge. In agreement with the percentage of QACs pre-adsorbed, the more hydrophobic the compound, the lesser the extent of desorption. Wastewater samples with activated sludge were supplemented with TTAB 200 mg L−1 and Ca-alginate beads containing the QACs-degrading microorganisms Pseudomonas putida A (ATCC 12633) and Aeromonas hydrophila MFB03. After 24 h, 10 mg L−1 of TTAB were detected in the liquid phase and 6–8 mg L−1 adsorbed to the sludge. Since without Ca-alginate beads or with empty beads total TTAB amount (phase solid and liquid) did not change, the 90% reduction of the initial 200 mg L−1 after treatment with immobilized cells was attributed to the bacterial consortium's capacity to biodegrade QACs. The results show the advantages of using immobilized bacteria to achieve complete QACs elimination from wastewater systems, thus preventing them from reaching the environment.

Development of an attract-and-kill co-formulation containing Saccharomyces cerevisiae and neem extract attractive towards wireworms.

Wireworms (Coleoptera: Elateridae) are major insect pests of worldwide relevance. Owing to the progressive phasing-out of chemical insecticides, there is great demand for innovative control options. This study reports on the development of an attract-and-kill co-formulation based on Ca-alginate beads, which release CO2 and contain neem extract as a bioinsecticidal compound. The objectives of this study were to discover: (1) whether neem extract can be immobilized efficiently, (2) whether CO2 -releasing Saccharomyces cerevisiae and neem extract are suitable for co-encapsulation, and (3) whether co-encapsulated neem extract affects the attractiveness of CO2 -releasing beads towards wireworms. Neem extract was co-encapsulated together with S. cerevisiae, starch and amyloglucosidase with a high encapsulation efficiency of 98.6% (based on measurement of azadirachtin A as the main active ingredient). Even at enhanced concentrations, neem extract allowed growth of S. cerevisiae, and beads containing neem extract exhibited CO2 -emission comparable with beads without neem extract. When applied to the soil, the beads established a CO2 gradient of >15 cm. The co-formulation containing neem extract showed no repellent effects and was attractive for wireworms within the first 24 h after exposure. Co-encapsulation of S. cerevisiae and neem extract is a promising approach for the development of attract-and-kill formulations for the control of wireworms. This study offers new options for the application of neem extracts in soil. © 2017 Society of Chemical Industry.

Enhanced biosorption of transition metals by living Chlorella vulgaris immobilized in Ca-alginate beads

ABSTRACTIn this study freely suspended and Ca-alginate immobilized C. vulgaris cells were used for the biosorption of Fe(II), Mn(II), and Zn(II) ions, from the aqueous solution. Experimental data showed that biosorption capacity of algal cells was strongly dependent on the operational condition such as pH, initial metal ions concentration, dosages, contact time and temperature. The maximum biosorption of Fe(II) 43.43, Mn(II) 40.98 and Zn(II) 37.43 mg/g was achieved with Ca-alginate immobilized algal cells at optimum pH of 6.0, algal cells dosage 0.6 g/L, and contact time of 450 min at room temperature. The biosorption efficiency of freely suspended and immobilized C. vulgaris cells for heavy metals removal from the industrial wastewater was validated. Modeling of biosorption kinetics showed good agreements with pseudo-second-order. Langmuir and D–R isotherm models exhibited the best fit of experimental data. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) revealed that the biosorption of considered metal ions was feasible, spontaneous and exothermic at 25–45°C. The SEM showed porous morphology which greatly helps in the biosorption of heavy metals. The Fourier transform infrared spectrophotometer (FTIR) and X-rays Photon Spectroscopy (XPS) data spectra indicated that the functional groups predominately involved in the biosorption were C–N, –OH, COO–, –CH, C=C, C=S and –C–. These results shows that immobilized algal cells in alginate beads could potentially enhance the biosorption of considered metal ions than freely suspended cells. Furthermore, the biosorbent has significantly removed heavy metals from industrial wastewater at the optimized condition.

Statistical optimization of arsenic biosorption by microbial enzyme via Ca-alginate beads

ABSTRACTBioremediation of arsenic using green technology via microbial enzymes has attracted scientists due to its simplicity and cost effectiveness. Statistical optimization of arsenate bioremediation was conducted by the enzyme arsenate reductase extracted from arsenic tolerant bacterium Pseudomonas alcaligenes. Response surface methodology based on Box–Behnken design matrix was performed to determine the optimal operational conditions of a multivariable system and their interactive effects on the bioremediation process. The highest biosorptive activity of 96.2 µg gm−1 of beads was achieved under optimized conditions (pH = 7.0; As (V) concentration = 1000 ppb; time = 2 h). SEM analysis showed the morphological changes on the surface of enzyme immobilized gluteraldehyde crosslinked Ca-alginate beads. The immobilized enzyme retained its activity for 8 cycles. ANOVA with a high correlation coefficient (R2 > 0.99) and lower “Prob > F”value (<0.0001) corroborated the second-order polynomial model for the biosorption process. This study on the adsorptive removal of As (V) by enzyme-loaded biosorbent revealed a possible way of its application in large scale treatment of As (V)-contaminated water bodies.

Entrapment of ball-milled biochar in Ca-alginate beads for the removal of aqueous Cd(II)

A novel adsorbent was synthesized through the entrapment of ball-milled biochar in Ca-alginate beads for the removal of aqueous Cd(II). Batch adsorption experiments were conducted to compare Cd(II) adsorption characteristics of ball-milled biochar (BMB), Ca-alginate (CA), and Ca-alginate entrapped ball-milled biochar (CA-BMB). All the tested adsorbents showed excellent sorption ability. The maximum Cd(II) adsorption capacity estimated with Langmuir isotherm modeling was 251.8mgg−1 for CA, 227.1mgg−1 for CA-BMB, and 40.0mgg−1 for BMB. The results demonstrate that entrapment of ball-milled biochar in Ca-alginate provides a low-cost and high-effective way for the removal of aqueous Cd(II).

Biosorption of transition metals by freely suspended and Ca-alginate immobilised with Chlorella vulgaris: Kinetic and equilibrium modeling

In this study, biosorption of Fe (II), Mn (II), and Zn (II) ions, from aqueous solution with free (non-immobilised) and Ca-alginate beads with immobilised Chlorella vulgaris biomass was investigated. Effects of pH, metal ions concentration, biosorbent dosages and contact time on the biosorption of selected metallic ions were studied. The maximum biosorption of Fe (II) 129.83, Mn (II) 115.90 and Zn (II) 105.29 mg/g was achieved with Ca-alginate immobilised microalgal biomass at optimum pH of 6.0, biomass dosage, 0.4 g/L, and contact time of 300 min and at 25 °C temperature. The biosorption efficiency of freely suspended and immobilised C. vulgaris biomass for the heavy metals removal from the industrial wastewater Palm Oil Mill Effluent (POME) was validated. The metallic ions biosorption on the Ca-alginate immobilised microalgae followed the pseudo-second-order kinetics model and the experimental data were well fitted to the Langmuir and D-R isotherm models. The calculated thermodynamic parameters, ΔGo, ΔHo and ΔSo exhibited that the biosorption of all tested metal ions onto freely suspended and Ca-alginate immobilised algal cells was feasible, spontaneous and exothermic in nature under observed conditions. The biosorption mechanism of C. vulgaris illustrated by FTIR and XPS showed bands conforming to CN, OH, COO, CH, CC, CS and C groups are closely related with the binding of heavy metals. The SEM showed porous morphology which greatly helps in the biosorption of heavy metals. This study confirmed that immobilisation of C. vulgaris in alginate beads constitute a favorable, effective, economical and biodegradable biosorbent material for the removal of heavy metals pollution in the environment.

Biodegradation of phenol by entrapped cell of Debaryomyces sp. with nano-Fe3O4 under hypersaline conditions

Phenol-containing industrial wastewater disposal has received much attention in recent years due to its toxicity and slow biodegradation. In this work, the isolated fungal strain Debaryomyces sp. was entrapped into Ca-alginate beads with nanoscale Fe3O4 to improve phenol biodegradation ability. Freely suspended cells as well as Ca-alginate immobilized cells without nanoscale particles were also prepared. Phenol removal by free cells and two kinds of Ca-alginate beads was evaluated with different initial phenol concentrations, temperatures, and salinities. The phenol biodegradation kinetics and optimal dosage of nano-Fe3O4 during the preparation of Ca-alginate beads were also determined. The results showed that immobilized Debaryomyces strain had better biodegradation performance than free cells under harsh conditions. Phenol removal rates were highest when using magnetically immobilized cells, followed by nonmagnetically cells. More than 99.9% of phenol was degraded within 80 h by immobilized cells with nano-Fe3O4 when initial phenol concentration was over 900 mg L−1 while the phenol removal efficiencies of free cell and immobilized cells without nano-Fe3O4 were 34.5% and 81.3%, respectively during the same periods of time. The reusability tests were carried out and the results indicated good stability of immobilized cells in saline environments, which was practical in actual industrial wastewater treatment.

Entrapment of DyP‐type peroxidase fromPseudomonas fluorescensPf‐5 into Ca‐alginate magnetic beads

The aim of this study was to investigate the optimal conditions for the immobilization and stabilization of DyP1B dye decolorizing peroxidases type B (DyP1B) from Pseudomonas fluorescens Pf-5 immobilized in Ca-alginate ferromagnetic beads. The immobilized DyP1B was used in the degradation of the Reactive Blue 5 (RB5) synthetic dye. The enzyme was successfully entrapped in a Ca-alginate matrix and showed an encapsulation efficiency of 94%. The concentration of DyP1B (0.8 mg mL-1 ), 2% of alginate and magnetite (10.0 mg mL-1 ) was optimal for immobilization. The immobilized DyP1B showed optimum activity at pH 7.0 and 40°C compared with pH 5.5 and 30°C for free peroxidase. Reusability studies showed that after five cycles, the immobilized DyP1B system retained more than 58% of its initial activity. The immobilized DyP1B was able to decolorize RB5 at concentrations of 0.1, 0.05, and 0.01% (w v-1 ) with efficiency rates of about 20, 29, and 45%, respectively. The immobilization of DyP1B in alginate beads with the addition of Fe3 O4 increased its catalytic and applicative potential.

Immobilization and Characterization of Bacillus Thuringiensis HCB6 Amylase in Calcium Alginate Matrix

Free enzyme in solution react with substrates to result in products which cannot be recovered for reuse. These problems can be overcome to a certain extent by the use of enzyme immobilization method. Immobilized enzymes are more robust and more resistant to condition changes. More importantly, the heterogeneous immobilized enzyme systems allow an easy recovery of both enzymes and products, multiple re-uses of enzymes, and continuous operation of enzymatic processes. Entrapment of enzymes in Ca-alginate is one of the simplest methods of immobilization. The aim of this research was to obtain the optimum condition of the making of immobilized amylase beads using a Ca-alginate bead and to determine its characteristics. The optimization of immobilized amylase beads includes variation of sodium alginates and variations of enzyme contact time with CaCl2. The characterization of immobilized amylase includes determination of optimum substrate concentration, optimum pH, and optimum incubation time as well as amylase stability test. Amylase activity was determined by using dinitro salicylic (DNS) method. The results showed that the optimum immobilized amylase obtained at alginate concentrations of 5% (w/v), contact time of 60 minutes and immobilization efficiency of 67.5%. Furthermore, immobilized amylase showed optimum substrate concentration of 1.5-2.5% (w/v), optimum pH of 6, an optimum incubation time of 20 minutes with the activity of 179.8 U/mL. The KM value for free amylase and immobilized amylases were 0.3 mM and 0.12 mM respectively. Vmax value for free amylase and immobilized amylases were 105.3 U/mL and 10.1 U/mL respectively. Immobilized Amylase can be used up to six times with the residual activity of 52.7%.

Treatment of oilfield wastewater using algal–bacterial fluidized bed reactor

ABSTRACTThis study was carried out to investigate the ability of an artificial microalgal–bacterial consortium to remediate an oilfield wastewater using laboratory-scale fluidized bed reactors (FBRs) under lighting. The consortium consists of an oil-degrading bacterial community and a microalgae, Scenedesmus obliquus GH2. The microbes were immobilized onto Ca-alginate beads and filled to the FBRs. The influence of hydraulic retention time (HRT) on the removal of chemical oxygen demand (COD), total nitrogen, NH3-N and oil concentration was investigated over 40 operational days. The synergistic relationship in the algal–bacterial microcosm was clearly demonstrated, since for the four parameters tested, the highest removal was recorded in the system inoculated with both algae and bacteria. In the algal–bacterial FBR, at 16 h HRT, the average effluent concentrations of COD, NH3-N and oil were 92, 24 and 4.8 mg/L, respectively, corresponding to removal efficiencies of 70.8%, 61.2% and 84.2%, respectively. The effluent could meet the grade 2 as required by the national discharge standard of China. However, the effluent quality of the bacterial- or algal-only case could not satisfy the grade 3 discharge standard at 16 h HRT. The algal–bacterial biomass exhibits lowest effluent microtoxicity and highest dehydrogenase activity in comparison with bacterial-only and algal-only cases. This study reveals that the consortium containing dual microbial species has potential for microbial remediation of oilfield wastewater.

Removal of copper and cadmium in acid mine drainage using Ca-alginate beads as biosorbent

Biosorption experiments were performed to investigate the ability of Ca-alginate beads as biosorbent for the removal of Cu and Cd in acid mine drainage (AMD). From the results of batch experiments, the removal efficiencies of both Cu and Cd for Ca-alginate beads were found to increase to 95% within 3 hours in the temperature range of 15–40 °C, indicating that it is possible to treat AMD using Ca-alginate beads within a short time period under various field conditions. For the column experiments, 381.8 g of Ca-alginate beads was packed in a Pyrex column (2.5 cm in diameter and 100 cm in height) and 119.7 liters (900 pore volumes) of AMD from the Ilgwang mine in Korea was successfully treated. The Cu and Cd removal efficiencies were maintained at levels higher than the Korean remediation goal (86% for Cu and 58% for Cd) and it was possible to treat more than 300 mL of AMD using only 1 g of Ca-alginate beads. Although AMD with a pH below 3 was injected into the column, the pH of the effluents was maintained above 3 for 1,140 pore volumes of flushing due to the buffer action of the beads. In SEM/EDS analysis of the Ca-alginate beads after the experiment, void spaces of the beads were found to be filled with precipitates of heavy metals, showing that Ca-alginate beads can be successfully used as a biosorbent for the removal of Cu and Cd in AMD.

Immobilized lignin peroxidase from Ganoderma lucidum IBL-05 with improved dye decolorization and cytotoxicity reduction properties

Use of free microbial enzymes for bioremediation and other industrial applications has several disadvantages like low stability and non-reusability in repeated batch operations. Immobilized enzymes are stable, recoverable and reusable in industrial processes. In this scenario G. lucidum IBL-05 LiP was entrapped in Ca-alginate beads using optimum concentrations of Na-alginate (4%), calcium chloride (0.2M) and glutraldehyde (0.02%). Optimum pH (pH 5) and temperature (55°C) for entrapped LiP were improved as compared to free LiP. Catalytic behavior of LiP also significantly enhanced, as Km value (0.25mM) decreased and Vmax value (868.6μmol/min) increased after ca-alginate entrapment of LiP. Decolorization efficiencies of Sandal reactive dyes after treating with immobilized LiP were in the range of 80–93%. A significant reduction was observed in water quality parameters including, BOD (66.44–98.22%), COD (81.34–98.82%) and TOC (80.21–97.77%) values. The cytotoxicity values for heamolytic and brine shrimp lethality of dye solutions treated with Ca-alginate immobilized LiP reduced up to 2.10–5.06% and 5.43–9.23%, respectively. On the basis of reduced toxicity and cytotoxicity values, it was concluded that Ca-alginate beads entrapped LiP may be an effective biocatalyst for bioremediation of dye based textile industry effluents.

Expression of chitinase gene in BL21 pET system and investigating the biocatalystic performance of chitinase-loaded AlgSep nanocomposite beads

Chitin, a polysaccharide, is abundant in nature and this substrate can be easily hydrolyzed by chitinase. Pharmaceutical and industrial applications of chitinase are considerably noteworthy, therefore in this study, high scale production of Chit36 enzyme was targeted using the E. coli pET expression system. The purified Chit36 enzyme was immobilized in Ca2+-cross linked alginate/sepiolite (AlgSep) nanocomposite beads for improving the catalytic activity and stability of Chit36 enzyme during the biocatalytic process. Immobilized enzymes require optimal conditions different from soluble enzymes. The AlgSep nanocomposite can save spatial structure and activity of the enzyme which is critical for enzyme immobilization. The catalytic activity and specific activity of the Chit36 entrapped in alginate nanocomposite beads were evaluated. Results showed that the activity of immobilized Chit36 in Ca-Alginate sepiolite composites beads (3.10±0.63U/g gel) was higher than that of immobilized Chit36 in Ca-alginate beads (3.95±0.40U/g gel). Also, the specific activity of Chit36 in AlgSep nanocomposite beads (22.9±1.521U/mg protein) was higher than the immobilized Chit36 in sepiolite-free alginate beads (8.52±0.758U/mg protein). The promising results obtained from this study would have beneficial pharmaceutical and industrial applications.

Co-encapsulation of amyloglucosidase with starch and Saccharomyces cerevisiae as basis for a long-lasting CO2 release.

CO2 is known as a major attractant for many arthropod pests which can be exploited for pest control within novel attract-and-kill strategies. This study reports on the development of a slow-release system for CO2 based on calcium alginate beads containing granular corn starch, amyloglucosidase and Saccharomyces cerevisiae. Our aim was to evaluate the conditions which influence the CO2 release and to clarify the biochemical reactions taking place within the beads. The amyloglucosidase was immobilized with a high encapsulation efficiency of 87% in Ca-alginate beads supplemented with corn starch and S. cerevisiae biomass. The CO2 release from the beads was shown to be significantly affected by the concentration of amyloglucosidase and corn starch within the beads as well as by the incubation temperature. Beads prepared with 0.1 amyloglucosidase units/g matrix solution led to a long-lasting CO2 emission at temperatures between 6 and 25 °C. Starch degradation data correlated well with the CO2 release from beads during incubation and scanning electron microscopy micrographs visualized the degradation of corn starch granules by the co-encapsulated amyloglucosidase. By implementing MALDI-ToF mass spectrometry imaging for the analysis of Ca-alginate beads, we verified that the encapsulated amyloglucosidase converts starch into glucose which is immediately consumed by S. cerevisiae cells. When applied into the soil, the beads increased the CO2 concentration in soil significantly. Finally, we demonstrated that dried beads showed a CO2 production in soil comparable to the moist beads. The long-lasting CO2-releasing beads will pave the way towards novel attract-and-kill strategies in pest control.