Demineralization Efficiency Research Articles

Photocatalytic degradation of reactive dyes over Ni[sbnd]Al layered double hydroxide

Due to the uncontrolled discharge of textile effluents, the extent of reactive dyes in wastewater is rising. Due to their toxicity, efficient removal becomes quite essential. In this report, NiAl layered double hydroxide (LDH) has been prepared using the coprecipitation methodology for the photocatalytic degradation of reactive dyes. The as-prepared materials were characterized by different techniques, such as DRS, XRD, FESEM, HRTEM, and XPS etc. The XRD pattern of the LDH confirms the formation of the rhombohedral (R3m) phase. The FESEM analysis reveals the irregular hexagon-like shape of the prepared LDH. The NiAl LDH has 98(1) and 87(1)% photodegradation efficiencies towards the removal of reactive blue 19 and reactive Red 120, respectively. The control experiments in the presence of different scavengers confirm that hydroxyl radicals and superoxide anions participate in photocatalytic degradation. The HRMS studies confirm the formation of different smaller fragments, thereby providing a deeper insight into the photodegradation mechanism. Moreover, the demineralization efficiency (88.9%) is quite close to the degradation efficiency for reactive blue 19, signifying practically complete demineralization of the pollutants. The recyclability studies ascertain the high stability of the photocatalyst. Therefore, the as-prepared NiAl LDHs can be considered a promising photocatalyst for the removal of reactive dyes from wastewater.

Valorization of marine by-products using green technology

In this work, two cases of marine by-product valorization using green technologies were highlighted, i.e., utilization of high-pressure carbon dioxide (HPCD) for demineralization of goldstripe sardinella (Sardinella gibbosa) scales and the use of non-specific enzymes for chitosan hydrolysis. After demineralization, type I collagen can be recovered from sardine scales. This work used HPCD process (of up to 10 bar or 1 MPa) to remove minerals from scales instead of the traditional strong acid method. Results from initial phase of the work showed that the process efficiency was significantly affected by pressure applied and treatment time (p < 0.05). And the demineralization efficiency reached was significantly lower than that achieved by treatment with hydrochloric acid (p < 0.05). In the second study, the chitosanolytic activity of four non-specific enzymes were assessed for chitosan hydrolysis. The results indicated that acid protease and cellulase could be a potential choice to produce chitooligosaccharides (COS) from shrimp shell.

Comprehensive characterization and evaluation of the process chain and products from Euphausia superba exocuticles to chitosan

AbstractAntarctic krill (Euphausia superba) is a source for compounds of high nutritive value. Within that process of extraction, exocuticles (shells) accumulate which are currently disposed. A valorization of the compounds of the exocuticle such as chitosan would be beneficial to avoid waste and to obtain a versatile polymer at the same time. In contrast to previous investigations focusing on chitosan production from whole krill, we applied and optimized process stages of the chitosan production from the exocuticles, performing a comprehensive analytical evaluation of the whole process, the side streams and the products for the first time. Degreasing was the first step resulting in a krill oil yield of 6.2% using ethanol. The fatty acid profile exhibited high contents of phospholipids (21.2%). Citric acid offered a demineralization efficiency of 93%. Deproteinization investigation revealed 2 M NaOH and 90°C for 2.5 h to be the best parameters, resulting in a deproteinization efficiency of 99.9% and a chitin content of 92.8%. The spectroscopic investigation indicated that the chitin has a crystallinity index of 76% and an acetylation degree of 88%. The deacetylation degrees of the resulting chitosans is determined to be 74%–88%, the molecular weight ranges from 102 to 126 kDa.

Degradation of marine crustacean shell wastes through single-stage co-fermentation using proteolytic and chitinolytic bacteria.

Management of crustacean shell waste (SW) through an eco-friendly technique is an environmental obligation to control pollution. The present study showed a novel approach through the simultaneous application of proteolytic and chitinolytic bacteria to effectively degrade unprocessed crustacean SW. For this, the bacteria with concurrent chitinolytic and proteolytic activity (Bacillus subtilis, Priestia megaterium, or Bacillus amyloliquefaciens) were applied either alone or in combination with one proteolytic strain (Paenibacillus alvei) in the unprocessed lobster, crab, and shrimp SW. The method degraded the shells with high deproteinization (> 90%) and demineralization efficiency (> 90%). The degradation was confirmed through scanning electron microscopy. The highest weight loss achieved with shrimp, crab, and lobster shells was 93.67%, 82.60%, and 83.33%, respectively. B. amyloliquefaciens + P. alvei combination produced the highest weight loss in crab and lobster SW, whereas all combinations produced statistically similar weight loss in shrimp SW. There was a concurrent production of N-acetyl glucosamine (up to 532.89, 627.87, and 498.95 mg/g of shrimp, lobster, and crab shell, respectively, with P. megaterium + P. alvei and B. amyloliquefaciens + P. alvei in all SW) and amino acids (4553.8, 648.89, 957.27 μg/g of shrimp, lobster, and crab shells, respectively with B. subtilis + P. alvei in shrimp and B. amyloliquefaciens + P. alvei in crab and lobster). Therefore, it is concluded that, for the first time, efficient degradation of crustacean shell waste was observed using chitinolytic and proteolytic bacterial fermentation with the obtention of byproducts, providing a basis for further application in SW management.

Microbial chitin extraction and characterization from green tiger shrimp waste: A comparative study of culture mediums along with bioprocess optimization

This research aims to introduce a low-cost, non-commercial culture medium and optimize the operating conditions for biological chitin extraction from green tiger shrimp waste in the Persian Gulf zone. For this purpose, the two most commonly used microorganisms, Bacillus licheniformis and Lactobacillus plantarum, were obtained to deproteinize and demineralize the shrimp shells within both culture mediums using a successive two-stage process. It was found that the proposed non-commercial culture medium was more efficient than the purchased and ready-to-use commercial medium and increased deproteinization and demineralization efficiency by 9 % and 11 %, respectively. According to the optimization, which was performed using a response surface methodology based on a central composite design, the demineralization model is more complicated than the deproteinization model. The presented model predicted deproteinization and demineralization yields with good accuracy. The FTIR results revealed that shrimp shells and chitin have similar main functional groups, while the degree of acetylation of the extracted chitin was 62.26 %. SEM results illustrated the formation of microfibrils and the chitin structure's porosity. The XRD data showed that the crystallinity index of chitin was 93.9 %. Besides, the thermal stability of the extracted chitin, with a maximum degradation temperature of 380 °C is comparable with the literature data.

Demineralization of common ivy-derived biomass and biochar and its effect on the resulting activated carbon properties

Biomass waste often contains high amounts of inorganic impurities, which is a limitation for developing high-quality bioproducts, e.g., high-purity activated carbons (ACs). Otherwise, these would be applicable to purify polluted water and air streams. Conventionally, AC’s are purified with non-sustainable and corrosive inorganic acids. This study illustrates the successful removal of the impurities from common ivy, Hedera helix L., through treatment with a natural deep eutectic solvent (NADES), namely choline chloride-malic acid (CCl:MA, 1:1 M). The demineralization efficiency is benchmarked against H2O and dilute hydrochloric acid (HCl). Moreover, the importance of the process sequence, pre- or post- pyrolysis demineralization, for AC-production was investigated. The three solvents showed different biomass (pre-pyrolysis) demineralization efficiencies, they were ranked, from best to worst, as follows: HCl > CCl:MA > H2O. However, demineralizing the biomass after pyrolysis yielded highly porous ACs, with a good mix of meso-and micropores. In this case, no differences in removal performance could be observed between HCl and CCl:MA. Lastly, the ACs phosphate adsorption capacity was highest after demineralizing biomass with either H2O or CCl:MA. Ultimately, this investigation demonstrated CCl:MA’s potential as a green demineralization agent to treat metal-contaminated biomass in future bio-refinery processes.

Ultrasound-Assisted Demineralization Process of Sugarcane Straw and Its Influence on the Further Biomass Conversion

Lignocellulosic materials have been considered as an alternative source from which liquid biofuel and fine chemicals can be produced with a moderate environmental impact. However, they can be contaminated with metals, soil, and ash, owing incrustation and corrosion of industrial reactors and pipelines. In this work, the use of ultrasound energy was applied for the removal of metals and nonmetals (Ba, Ca, Mg, Mn, P, S, Si, and Sr) from sugarcane straw. Ultrasound-assisted demineralization (UAD) experiments were carried out in ultrasonic baths in several frequencies (from 25 up to 130 kHz). The following experimental conditions were evaluated: demineralization solution (HNO3, HCl, H2SO4, H2O2, and H2O), H2O2 concentration (from 5 to 30% v v−1), extraction temperature (from 30 to 70 °C), sonication time (from 5 to 45 min), and ultrasound amplitude (from 10 to 70%). Better demineralization efficiencies (66%) were obtained employing an ultrasound bath operating at 25 kHz for 30 min, ultrasound amplitude of 60%, and using a diluted H2O2 solution (15% v v−1) at 70 °C. When the obtained results were compared with those obtained by mechanical stirring (MS, 500 rpm), it was observed that the use of ultrasound energy increased the demineralization efficiency up to 16%. Furthermore, acid hydrolysis was performed to evaluate the influence of US and mechanical stirring in fermentable sugars’ production. The total sugars’ yield (glucose, xylose, and arabinose) increased around 55% for both systems (US and MS). To prove the applicability of the proposed process, some experiments for scaling up were performed using several reaction loads (0.5 to 3 L). An attempt for scaling the proposed process up was well succeeded up to a 3 L load. Therefore, the proposed ultrasound-assisted procedure can be considered as a suitable alternative for high-efficiency demineralization from sugarcane straw.

Purification of Chitin from Pupal Exuviae of the Black Soldier Fly

PurposeChitin purification from remains (pupal exuviae after metamorphosis to adult flies) of Hermetia illucens farming was optimized performing demineralization, deproteinization and bleaching under different conditions. The optimal parameters to obtain high-purity chitin were determined.MethodsDried and ground pupal exuviae, whose composition was initially determined, were demineralized using six different acids. Proteins were removed with a NaOH treatment in which temperature, molarity and duration were varied in a randomized experiment. Bleaching was carried out testing ten different chemicals, including NaOCl, H2O2, solvent mixtures and enzymes. The efficiency of each step was determined to assess the optimal conditions for each of them. The resulting chitin was subjected to spectroscopic characterization.ResultsThe highest demineralization efficiency (90%) was achieved using 0.5 M formic acid for 2 h at 40 °C, confirming the validity of organic acids as a more sustainable alternative to inorganic acids. The treatment with 1.25 M NaOH at 90 °C for 4 h showed the highest deproteinization efficiency, removing 96% of the proteins. Temperature and NaOH concentration were the significant parameters for deproteinization efficiency. The most efficient bleaching treatment was with 6% NaOCl at 60 °C for 1 h (67% efficiency). H2O2 could also be a valid alternative to avoid environmental risk related to chlorine-containing compounds. At the end of the purification process 17% of the original biomass was retained with a chitin content of 85%, corresponding to a chitin yield of 14% related to the initial biomass. Solid-state nuclear magnetic resonance showed that the purified chitin had a degree of acetylation of 96% and X-ray powder diffraction gave a crystallinity index of 74%.ConclusionThis investigation shows an optimized method for extraction of high-purity chitin from H. illucens pupal exuviae, supporting the validity of insect-farming remains as source of this versatile biopolymer.Graphical

Visualization characterization of minerals touched by interconnected pores and fractures and its demineralization effect on coal permeability during CO2-ECBM process based on X-ray CT data

The purpose of this study is to visually reconstruct the minerals touched by connected pores and fractures and reveal their demineralization process, which is of great significance for the analysis of permeability evolution during CO2-ECBM process. Two samples collected from Qinshui basin were taken as the research object. Firstly, the definition, reconstruction, and demineralization processes of such minerals were realized, and the evolution of pore network model under different demineralization efficiencies was discussed. Then, the analysis of geological and mathematical models for permeability evolution was realized with the pore network model as the geological carrier, and the influence of such minerals under different demineralization efficiencies on coal permeability was discussed. Finally, the application and its mechanism of demineralization process in CO2-ECBM process were further discussed. The results show that the minerals touched by interconnected pores and fractures extracted can be divided into five groups with the same volume, that is the demineralization efficiency is 20%, 40%, 60%, 80% and 100%, respectively, and each group can be independently removed from sample to merge into the pore and fracture space. The differences in spatial distribution between the aggregate phase of pore, fracture and mineral and the mineral phase touched by interconnected pores and fractures indicate that the presence of minerals touched by interconnected pores and fractures will have a great influence on the connectivity of pore and fracture. The connectivity of pore and fracture gradually increases with the increase of demineralization efficiency, and only the removal of such mineral can produce good connectivity. With the increase of demineralization efficiency, pore and fracture are completely interconnected, and pore volume and throat area significantly increase, which can form better pore network model. With the gradual increase of demineralization efficiency, the minerals in interconnected pore and fracture are gradually reduced, and the secondary porosity is gradually increased, which leads to the gradual expansion of the size of pore and fracture, and the gradual increase of the connectivity. The demineralization of the minerals touched by interconnected pores and fractures during the CO2-ECBM process is conducive to the realization of engineering of CO2-ECBM technology.

Chemometric Optimization of a Demineralization Method for Analysing Sediment Organic Matter by Fourier Transform Infrared Spectroscopy

Fourier transform infrared (FTIR) spectroscopy is a widespread and useful technique for characterizing the chemical composition of soil/sediment organic matter (SOM). However, the mineral components of the samples limit spectral analysis since they mask SOM’s distinctive signals. Big efforts have been made in this matter to eliminate the spectral interferences of mineral constituents of the samples, by demineralization with hydrofluoric acid (DHF), or spectral subtraction. This work aimed to upgrade reported DHF methods and optimize a sample preparation methodology for SOM characterization by FTIR spectroscopy combining the potential of spectral and multivariate analysis. Semi-quantitative FTIR ratios were introduced as input variables for principal component analysis to determine the optimal DFH conditions to characterize SOM. One-way analysis of variance (ANOVA, α = 0.05) test revealed that the optimal demineralization was achieved with two cycles of HF 10% v/v at 60 °C, against five HF cycles and room temperature, previously reported. The DHF at the optimal conditions not only improved the demineralization efficiency against that of the reported methods but also did not cause significant undesirable modifications in SOM that could distort the FTIR analysis. These conclusions have statistical significance and are based on the qualitative information of the spectra and also on a comprehensive semi-quantitative study of them.

Establishment of successive co-fermentation by Bacillus subtilis and Acetobacter pasteurianus for extracting chitin from shrimp shells

To simplify the process of chitin bio-extraction from shrimp shells powder (SSP), successive co-fermentation using Bacillus subtilis and Acetobacter pasteurianus was explored in this work. Among three protease-producer (B. licheniformis, B. subtilis, and B. cereus), only B. subtilis exhibited high compatibility with A. pasteurianus in co-culture. Successive co-fermentation was constructed as follows: deproteinization was performed for 3 d by culturing B. subtilis in the medium containing 50 g·L−1 SSP, 50 g·L−1 glucose, and 1 g·L−1 yeast extracts; After feeding 5 g·L-1 KH2PO4 and 6 % (v/v) ethanol, A. pasteurianus was cultured for another 2 d without replacing and re-sterilizing medium. Through 5 d of fermentation, the final deproteinization, demineralization efficiency, and chitin yield reached 94.5 %, 92.0 %, and 18.0 %, respectively. This purified chitin had lower molecular weight (12.8 kDa) and higher deacetylation degree (19.6 %) compared with commercial chitin (18.5 kDa, 6.7 %), and showed excellent structural characterization of FESEM and FT-IR analysis.

Valorization of side-streams from lactose-free milk production by electrodialysis

Lactose-free milk production generates large volumes of a by-product, rich in lactose, known as nanofiltration retentate (NFR). However, enhancing the value of this by-product is challenging due to the presence of high concentration of minerals which are believed to induce a salty and bitter taste. To overcome this issue, the present project aims to study the feasibility of an electrodialysis (ED) process for demineralization of NFR. In addition to native NFR, two subsequent dilutions of NFR were tested reducing the electric conductivity from 5.5 ± 0.2 to 4.7 ± 0.3 and 3.7 ± 0.1 mS·cm−1 while three voltages of 5, 10 and 15 V during ED were applied. The ED efficiency was measured in terms of demineralization rate, mineral removal kinetics, system resistance and energy consumption during the process. A demineralization level higher than 90% was reached within 120 min without significant loss of lactose. But, total nitrogen content was lost to some extent. The demineralization rate and energy consumption increased with the applied potential, where the demineralization efficiency declined significantly after 80% for all processing conditions. A predictive model was therefore developed to estimate the time required for 80% of demineralization as a function of initial conductivity and voltage applied.

Electrophysical characteristics of the desalination plant based on the principle of capacitive deionization

The basic electrophysical and technological parameters of a CDI desalination plant designed for long-term operation, based on the principle of salt solution deionization on electrodes with a developed surface, have been studied. The proposed equipment for water demineralization uses a simplified design with pumping the solution through electrodes (“flow through electrodes”), which allows bypassing without relatively expensive ion-exchange membranes. Non-woven felt “Karbopon-V-Aktiv-200-65A” was used as the electrode material, the estimated value of the specific surface of the material of which, according to the results of measurements by the method with the deposition of acetone, amounted to ~ 1000 m2/g or more. Also, the advantages of the proposed CDI desalination plant are the absence of highly loaded power elements, the use of corrosion-resistant materials and the reliability of the electrode stacking scheme, which makes it possible to count on its long-term and reliable operation. Various possibilities of operational adjustment of the desalination plant modes are demonstrated – reduction of the discharge period due to the application of voltage pulses of reverse polarity, increasing efficiency by organizing a procedure for taking into account the real voltage at the working electrodes inside the CDI cell. The high-energy efficiency of demineralization is determined by the relatively low operating voltage of ~ 1 V. It is established that with increasing amperage, salt removal is more efficient, respectively, the degree of desalination is higher at a higher current: the working period of 30 minutes corresponds to the degree of desalination of ~ 20 % at a voltage of 1.4 V and ~ 30 % in the 1.6 V mode. The possibility of increasing the desalination capacity to ~ 100 g of salt over a half-hour period was noted. Possible ways to further improvement of the performance of the equipment presented in the article are identified.

A comparative study on demineralization of coals by acid-washing and solvent-extraction methods for low temperature catalytic coal gasification application

Catalytic coal gasification is an efficient way to achieve high conversion rates at low temperatures. Catalyst loss due to the reaction between the inherent mineral matter in the coal and the catalyst is a major hurdle for its practical application. The problem may be overcome by removing the mineral matter from the coal before use. Two demineralizing approaches, acid-washing and solvent-extraction methods are investigated for demineralizing the coals. Elemental analysis, XRD analysis, NMR analysis, and N2 adsorption analysis were made to compare the demineralization efficiency, crystallographic carbon microstructure, chemical structure, and micro-porosity, respectively. Solvent-extraction method was found be more efficient for demineralization. Difference was observed in the chemical structure and micro-porosity while crystallographic carbon-microstructure was found to be similar. Non-catalytic and catalytic gasification reactivity of the chars obtained by the two methods was compared. Gas composition and gas evolution profiles were also obtained and found to be influenced by the degree of demineralization.

Two-Step Separation of Chitin from Shrimp Shells Using Citric Acid and Deep Eutectic Solvents with the Assistance of Microwave.

In this research, a two-step extraction approach was developed for chitin preparation from shrimp shells by utilizing citric acids and deep eutectic solvents (DESs), which effectively removed minerals and proteins. In the first step, minerals of shrimp shells were removed by citric acid, and the demineralization efficiency reached more than 98%. In the second step, the removal of protein was carried out using deep eutectic solvents with the assistance of microwave, and the deproteinization efficiency was more than 88%. The results of scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction analysis (XRD), and thermogravimetric analysis (TGA) showed that the quality of DES-prepared chitin was comparable to that of traditional acid/alkali-prepared chitin. These results were realized without utilizing hazardous chemicals, which are detrimental to the environment. This research indicates that a DES-based preparation approach has the potential for application in the recovery of biopolymers from natural resources.

Simultaneous fermentation and hydrolysis to extract chitin from crayfish shell waste

Chitin is the second-most abundant bioresource and widely used in the food, agricultural, textile, biomedical, and pharmaceutical industries. However, an efficient, environmentally friendly, and economically feasible process for chitin extraction from shellfish waste remains to be explored. This study aimed to extract chitin from crayfish shell waste powder (CSP) by removing Ca2+ and protein, using Bacillus coagulans LA204 and proteinase K. A simultaneous enzymatic hydrolysis and fermentation process was conducted at 50 °C with 5% (w/v) CSP, 5% (w/v) glucose, 1000 U proteinase k g−1 CSP, and 10% inoculation of B. coagulans LA204 in a 5-L bioreactor under non-sterile conditions. After 48 h of fermentation, the deproteinization efficiency, demineralization efficiency, and chitin recovery reached 93%, 91%, and 94%, respectively. 1 mol additional glucose efficiently removed 0.91 mol calcium carbonate and 93% of the removed protein was hydrolyzed to acid-soluble protein. Simultaneous enzymatic hydrolysis and fermentation was a new strategy and a competitive biological method for chitin extraction.

Investigation of electrodialysis anti-fouling configuration for desalting and treating tannery unhairing wastewater: Feasibility of by-products recovery and water recycling

The desalination and treatment of tannery unhairing wastewater by electrodialysis (ED) is investigated in this research in order to separate, concentrate, recover and reuse low molecular weight charged species (S2−, HS−, OH−, Cl−, Ca2+, Na+ and amino acids), and to separate proteins and recycle treated water. Therefore, a novel electrodialysis membrane configuration was proposed. This was based on a double anti–fouling membrane. The ED anion exchange membrane (AEM), which is very sensitive to organic fouling, was protected by an ultra filtration membrane impermeable to the negatively charged proteins that could not reach the AEM surface. The experimental results were quite promising, and in spite of only one desalination compartment ED cell; the demineralization efficiency was 56 ± 1.25% (5.5–2.4 mS/cm), with a sensitive removal of sulphide, calcium and chloride. The organic matter (protein, peptides…) was isolated in the dilute compartment. The most important result was the total absence of membrane fouling.The experimental results remarkably proved the initial hypothesis, and suggested promising solutions for industrial pollution, where the membrane processes have never been successful.

Chitin extraction from crab shells by Bacillus bacteria. Biological activities of fermented crab supernatants

Crab shells waste were fermented using six protease-producing Bacillus species (Bacillus subtilis A26, Bacillus mojavensis A21, Bacillus pumilus A1, Bacillus amyloliquefaciens An6, Bacillus licheniformis NH1 and Bacillus cereus BG1) for the production of chitin and fermented-crab supernatants (FCSs). In medium containing only crab shells, the highest demineralization DM was obtained with B. licheniformis NH1 (83±0.5%) and B. pumilus A1 (80±0.6%), while the highest deproteinization (DP) was achieved with A1 (94±1%) followed by NH1 (90±1.5%) strains. Cultures conducted in medium containing crab shells waste supplemented with 5% (w/v) glucose, were found to remarkably promote demineralization efficiency, and enhance slightly deproteinization rates. FTIR spectra of chitins showed the characteristics bands of α-chitin.FCSs showed varying degrees of antioxidant activities which were in a dose-dependent manner (p<0.01). In fact, FCS produced by B. amyloliquefaciens An6 exhibited the highest DPPH free radical-scavenging activity (92% at 4mg/ml), while the lowest hydroxyl radical-scavenging activity (60% at 4mg/ml) was obtained with B. subtilis A26 hydrolysates. However, the highest reducing power (OD700nm=2 at 0.5mg/ml) was obtained by B.amyloliquefaciens An6 hydrolysates. These results suggest that crab hydrolysates are good sources of natural antioxidants. Further, FCSs were found to exhibit antibacterial activity against Gram-positive and Gram-negative bacteria.

Biotechnological process of chitin recovery from shrimp waste using Lactobacillus plantarum NCDN4

Chitin in shrimp waste is tightly associated with proteins, lipids, pigments and mineral deposits. Therefore, these source materials have to be pretreated to remove these components. For a long time, chemical process has been used widely for extraction of chitin from shrimp waste. The chemical process however led to severe environmental damage and low chitin quality. The biological process has been shown promising to replace the harsh chemical process to reduce the environment impact. In our previous study chitin recovery from sterilized shrimp waste by Lactobacillus plantarum NCDN4 was investigated. However in large scale it is uneconomical to sterilize the shrimp waste. For that reason, in this study the microbial process using Lactobacillus plantarum NCDN4 for chitin recovery from unsterilezed shrimp waste has been investigated. Factors affecting the demineralization by this strain such as inoculum size, glucose concentration, initial pH, NaCl concentration and fermentation time were investigated. It was found that when unsterilized shrimp waste fermented with 20% L. plantarum inoculum, 12,5% glucose, and pH 6 for 4 days at 30°C, 99. 28% demineralization and 48.65% deproteination could be achieved. The ash and protein content of fermented residues were 1.33% and 22.46% respectively. Compared to sterilized condition the efficiency of demineralization and deproteination was similar.&#x0D; Chitin trong phế liệu tôm liên kết chặt chẽ với protein, sắc tố và khoáng. Do vậy để thu được chitin cần có các bước tiền xử lí để loại các thành phần không phải chitin ra. Phương pháp hóa học được sử dụng rộng rãi từ lâu để tiền xử lí chitin. Tuy nhiên do phương pháp hóa học gây hại cho môi trường và tạo ra chitin chất lượng thấp, các nhà khoa học nỗ lực nghiên cứu tìm ra các phương pháp thay thế. Phương pháp sinh học được xem là rất khả quan để thay thế phương pháp hóa học. Trong nghiên cứu trước của chúng tôi, quá trình lên men phế liệu tôm thanh trùng bằng Lactobacillus plantarum NCDN4 đã được nghiên cứu. Tuy nhiên việc thanh trùng phế liệu tôm không kinh tế. Trong nghiên cứu này quá trình lên men phế liệu tôm không thanh trùng bằng Lactobacillus plantarum NCDN4 đã được khảo sát. Các yếu tố như tỷ lệ giống, nồng độ đường glucose, nồng độ NaCl, pH ban đầu của môi trường lên men và thời gian lên men đã được nghiên cứu. Kết quả cho thấy ở điều kiện 20% giống theo thể tích, 12,5% dịch đường glucose, 2% muối theo khối lượng, pH ban đầu 6, sau 5 ngày lên men lượng khoáng và protein trong nguyên liệu giảm tương ứng 99.28% và 48.65%. Lượng khoáng và protein còn lại tương ứng 1.33% và 22.46% (tính theo trọng lượng khô). So với phế liệu tôm không thanh trùng, hiệu quả loại khoáng và protein là tương đương.

Optimization of chitin extraction from shrimp waste with Bacillus pumilus A1 using response surface methodology

Chitin extraction from shrimp shells by biological treatment, using the Bacilli Bacillus pumilus A1, is a non-polluting method and offers the opportunity to preserve the exceptional qualities of chitin and its derivatives. However, the major disadvantage of the fermentative way is the low efficiency of demineralization and deproteinization. The aim of this study is to improve the yield of extraction which depends on many factors, such as the medium composition and the physical parameters. In order to look for the optimal conditions, a Plackett and Burman design was carried out to screen eight factors influencing the deproteinization and demineralization efficiencies. The four most influencing variables were then examined to achieve the optimization using a central composite design. The results obtained showed that the optimal conditions were: shrimp shell concentration of 70g/l, glucose concentration of 50g/l, pH of 5.0 incubated with 0.225 OD of B. pumilus A1 inoculum, at 35°C and 150rpm for 6 days in 500ml flask containing 100ml of working volume. These conditions led to 88% of demineralization and 94% of deproteinization. 13C CP/MAS NMR spectral analysis of the chitin prepared was carried out and was found to be similar to that of the commercial α-chitin.