Optimal Hydrolysis Conditions Research Articles

Microwave-assisted Degradation of Poultry Feather to Synthesize Protein-based Surfactant

Poultry feather is hydrolyzed into peptides and amino acids in sub-critical water without any acid or alkali as catalyst under microwave-assisted heating to produce protein-based surfactant. The optimal hydrolysis condition is as follows: temperature 200 °C, time 60 min, and the yield of peptides and amino acids 84.31%. The critical micelle concentration (CMC) and surface tension of the product of peptides and amino acids are 2.6 g/L and 48.2 mN/m. In order to increase lipophilicity, subsequently anionic protein-based surfactant was synthesized by acylation reaction between the hydrolysis product of peptides and amino acidsand oleoyl chloride. The CMC and surface tension decreased greatly with linkage with oleoyl. The synthesized anionic surfactant with weight ratios of 10% (wt.%) hydrolysis liquid/oleoyl chloride of 3:1, 4.5:1 and 6:1 are 0.5, 0.7 and 0.8 g/L and corresponding surface tension are 30.1, 34.0 and 35.7mN/m.

Enzymatic Hydrolysis of Defatted Antheraea pernyi (Lepidoptera: Saturniidae) Pupa Protein by Combined Neutral Protease Yield Peptides With Antioxidant Activity.

In this study, peptides were prepared from defatted Antheraea pernyi (Lepidoptera: Saturniidae) pupa protein via hydrolysis with combined neutral proteases. Single-factor tests and response surface methodology (RSM) were used to determine the optimal hydrolysis condition suitable for industrial application. Optimal hydrolysis of the defatted pupa protein was found to occur at an enzyme concentration of 4.85 g/liter, a substrate concentration of 41 g/liter, a hydrolysis temperature of 55°C, and a hydrolysis time of 10 h and 40 min. Under these conditions, the predicted and actual rates of hydrolysis were 45.82% and 45.75%, respectively. Peptides with a molecular weight of less than 2,000 Da accounted for 90.5% of the total peptides generated. Some of the peptides were antioxidant peptides as revealed by sequencing and functional analysis. The antioxidant activity of the mixed peptides was subsequently confirmed by an antioxidant activity assay. The results showed that peptides with high antioxidant activity could be obtained from the hydrolysis of A. pernyi pupa protein.

Screening of some catalytic activities of mature berries of Solanum aethiopicum cultivar "Klongbo"

Aubergines of the Solanum aethiopicum cultivar "Klongbo" are widely cultivated and consumed by the Ivorian population. However, their post-harvest conservation is problematic. In order to prevent their post-harvest degradation, this study initiates the screening of enzymatic activities responsible for hydrolysis and oxidation activities in the berries of Solanum aethiopicum cultivar "Klongbo". Among the enzymatic activities tested, phosphatases, N'Acethylglucosaminidase, dopamineoxydase and pyrocatecholoxydase were the predominant enzymatic proteins. The optimum hydrolysis and oxidation conditions in terms of pH and temperature are listed as follows: phosphatases (pH 8.0; 50°C), N-acetylases (pH 5.6; 45°C), dopamineoxydase (pH 9.6; 10°C) and pyrocatecholoxydase (pH 9.0; 10°C). Cu2+ ions inhibit all tested enzymatic activities and especially Zn2+ ions for polyphenoloxidase activities. EDTA has an inhibitory effect on phosphatase and N'acetylase activities. SDS has an inhibitory effect on dopamineoxydasic, pyrochatecholoxydasic and phosphatasic activities. On the other hand, it has no effect on N'Acethylglucosaminidasic activities.

Optimization of chemical and enzymatic hydrolysis for production of chicken blood protein hydrolysate rich in angiotensin-I converting enzyme inhibitory and antioxidant activity

Response surface methodology was adopted to optimize hydrolysis conditions for the production of antioxidant and angiotensin-I converting enzyme (ACE) inhibitory peptides from chicken red blood cells by both enzymatic and acid hydrolysis. During acid hydrolysis, temperature (P < 0.001) and acid concentration (P < 0.001) influenced the degree of hydrolysis (DH%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the hydrolysate while ACE inhibitory activity of the hydrolysate was strongly influenced by acid concentration (P < 0.001). Temperature and time of hydrolysis had no effect (P > 0.05) on the ACE inhibitory activity of the hydrolysate. Acid hydrolysis conditions of 50°C, 32 h, and 0.03 N hydrochloric acid resulted in optimum DH% (33.1%), optimum DPPH scavenging activity (46%), and optimum ACE inhibitory activity (43.7%) of the hydrolysate. During enzymatic hydrolysis of chicken red blood cells, DH% was influenced by the temperature of hydrolysis (P < 0.001) and enzyme concentration (P < 0.001). DPPH scavenging of the hydrolysate was marginally (P < 0.05) influenced by the temperature of hydrolysis and ACE inhibitory activity of the hydrolysate was highly influenced by temperature (P < 0.001) and enzyme concentration (P < 0.001). Enzyme hydrolysis conditions of 60°C, 150 min, and 2.5% alcalase resulted in maximum DH% of 63.9%, while the highest DPPH scavenging activity (75%) of hydrolysate was observed under the hydrolysis conditions of 60°C, 30 min, and 2.5% of the enzyme. Optimum ACE inhibitory activity (45%) of the hydrolysate was achieved at hydrolysis conditions of 2.5% alcalase, 120 min of hydrolysis at 60°C. ACE inhibitory activity of the enzymatically hydrolyzed product was directly proportional to DH%, while DPPH activity was inversely proportional to DH%. DPPH scavenging activity of the acid hydrolysate was recorded at a lower range (34.8–56.9%) compared to the enzyme hydrolysate (40.4–77.4%), while ACE inhibitory activity of both the hydrolysates was observed in the same range (18.7–49.4 and 14.2–47.7% for acid and enzyme hydrolysate, respectively). This study indicated that chicken red blood cells could be successfully hydrolyzed by both chemical and enzymatic methods to obtain hydrolysates having antioxidant and ACE inhibitory activity.

Ultrasonic-alkali method for synergistic breakdown of excess sludge for protein extraction

Excess sludge is rich in proteins that can be recovered to prepare protein foaming agents and other products with high added value. To extract sludge proteins efficiently, more sludge proteins can be dissolved into the liquid phase by destroying sludge flocs and microbial cell structures. The commonly used alkali-thermal hydrolysis method has the disadvantages of high energy consumption and the additional Maillard reaction. Ultrasonic-alkali hydrolysis (UA) has been widely used as pretreatment for sludge anaerobic digestion, and the effect of UA on cell wall cracking gives it potential application prospects in sludge protein extraction. This study evaluated the potential of UA for sludge protein extraction, and the experimental conditions were optimized to explore the foaming performance of sludge proteins based on a single-factor experiment and orthogonal experiment. The results showed that under optimum hydrolysis conditions (pH of 12, sludge moisture content of 94%, ultrasonic power density of 1.7 W/mL, and ultrasonication duration of 24 min), the protein yield and protein extraction efficiency (RP) were 366.3 mg/g total solids (TS) and 81.4%, respectively. UA converted more than half of the proteins into polypeptides and thus promoted the foaming performance of the sludge proteins to meet the relevant standards for foaming agents. The dewatering performance of the hydrolysed sludge was improved by 93.4%, which was convenient for subsequent treatment. Further research illustrated that UA could shorten the treatment time of alkali hydrolysis (AH) by 36 times when achieving a similar protein yield, and the protein yield produced by UA was 11.4 times greater than that produced solely by ultrasonic hydrolysis (US), indicating that a synergistic effect occurred when AH was combined with US.

Optimization of Cellulase Immobilization with Sodium Alginate-Polyethylene for Enhancement of Enzymatic Hydrolysis of Microcrystalline Cellulose Using Response Surface Methodology.

A novel method of immobilizing cellulase on sodium alginate (SA)-polyethylene glycol (PEG) enabled the cellulase to be used repeatedly. The matrix of the immobilized cellulase was detected and characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. In comparison with SA-immobilized cellulase, the relative enzyme activity and immobilization rate increased by 25% and 18%, respectively. The application range of the immobilized enzyme in terms of temperature and pH was larger than that of the free enzyme, and its thermal stability increased. The immobilized enzyme was used in enzymatic hydrolysis, in which MCC was used as the substrate. The optimal conditions for enzymatic hydrolysis were as follows: the dosage of SA-PEG-immobilized cellulase was 3.55 g/g total solids of the substrate, the concentration of the substrate was 13.16%, and the pH was 5.11. In comparison with the yield of reducing sugars in the first round of hydrolysis of MCC by SA-immobilized cellulase, the yield in the hydrolysis of MCC by SA-PEG-immobilized cellulase increased by 133%. After five cycles of repeated use, the total yield of reducing sugars when MCC was hydrolyzed by SA-PEG-immobilized cellulase was similar to that achieved with free cellulase. In comparison with the free enzyme, the highest yield when the immobilized enzyme was used was 22.68%. Therefore, the immobilized cellulase exhibited high performance in enzymatic hydrolysis.

Response Surface Optimization of Enzymatic Hydrolysis of Peptides of Chinese Pecan (Carya cathayensis) and Analysis of Their Antioxidant Capacities and Structures

Pecan cake, a by-product of pecan processing, has not been fully developed and utilized. It contains proteins with high nutritional value that can be used as a potential source of bioactive peptides. In this study, the compound protease from the four common proteases was selected as the best protease, and the best hydrolysis was determined via response surface optimization. The optimal hydrolysis conditions were as follows: 55 ℃, pH 7.7, 3900 U/g protease concentration, and 2 h. Under these conditions, peptide yield and total antioxidant capacity (TAC) were 34.1 % ± 0.2 % and 1.1 ± 0.1 mmol/g, respectively. The peptides showed desirable 1,1-diphenyl-2-picrylhydrazyl (DPPH) (IC50: 0.2 mg/mL) and 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) (IC50: 0.4 mg/mL) radical scavenging capacities, which were found to be related to their amino acid compositions, molecular weights, and structures. The molecular weight of the peptides obtained from the pecan cake protein hydrolyzed by the compound protease was < 3 KDa, with their contents reaching 94.0 % ± 0.4 %. The yield of protein hydrolysate from pecan cake was about 7.2 %. HPLC analysis revealed that the content of hydrophobic amino acids in the peptides was relatively high. Fourier transform infrared spectroscopy and X-ray diffraction analysis showed that hydrolysis gradually changed the structure of the proteins from ordered to disordered, thereby exposing more antioxidant groups. α-helix and β-turn angles decreased from 29.5 % and 24.9–20.3 % and 15.2 %, respectively. β-sheet, β-antiparallel, and random coil increased from 24.2 %, 7.7 %, and 13.7–33.5 %, 9.3 %, and 21.8 %, respectively.

INTRODUCTION OF BIOFUELS AS A WAY OF SOLVING ECOLOGICAL PROBLEMS

Since environmental issues have become a priority for everyone on the planet, and the fact that growing demand for fossil fuels will soon lead to a reduction in world reserves, except for climate change due to their use and greenhouse gas emissions. The aim of this work was to assess the potential for the introduction of biofuels and find the optimal conditions for the enzymatic hydrolysis of Japonica Rice husk. In addition, evaluate the positive and negative consequences because of the use and implementation of this technology. The methodology used variables: substrate FPU, pH, time, temperature and concentration surfactants using the screening construct obtained statistically, all variables are significant. Then an optimization plan was applied for the variables: pH, FPU and time, dropping those with a lower level of significance. Finally, the best conditions found in previous projects were (pH 5.0, 13 h, and 30 FPU / g of substrate); later, these conditions were applied in experiments to assess the effect of an increase in hydrolyzed cellulose. They use 6%; 8% and 10% of pulp is available with a recycling yield of 74%, 42% and 16%. The community has its own interests in the use of biofuels; therefore, this study provides an opportunity for biofuel producers to reduce environmental, economic, and social costs.Keywords: biofuel; environment; alternative energy; bioethanol. JEL Classifications: C30, D12, Q41, Q48DOI: https://doi.org/10.32479/ijeep.10686

Keratin particles generated from rapid hydrolysis of waste feathers with green DES/KOH: Efficient adsorption of fluoroquinolone antibiotic and its reuse

Fluoroquinolone antibiotics are widely used in human and veterinary medicine. However, untreated fluoroquinolone seriously threatens the ecosystem and human health. In this study, deep eutectic solvents (DESs) were applied for the hydrolysis of waste feathers, and the keratin particles (KPs) in a low-cost teabag were utilized to adsorb fluoroquinolone norfloxacin. Results showed that choline chloride/ethylene glycol DES rapidly hydrolyzed feathers within 10 min, and the undissolved particles effectively adsorbed norfloxacin. Adding KOH markedly shortened the hydrolysis time (6 min) and increased the adsorption ability of KPs. The optimum hydrolysis conditions were DES ratio of 1 g: 4.67 g, KOH of 35.68 g L−1, and temperature of 90 °C. When KPDES+KOH of 2 g L−1, norfloxacin of 25 mg L−1, and pH0 7 were used, 94% of norfloxacin was removed in 60 min. A low-cost teabag effectively separated the KPs from the solution after adsorption and did not decrease the adsorption ability of the KPs. The Langmuir isotherm model well described the adsorption behavior of KPsDES+KOH (qmax = 79.36 mg g−1, R2 = 0.9972). In addition, acetone efficiently regenerated the exhausted KPsDES+KOH. The KPs maintained >80% of its adsorption ability after seven cycles of regeneration.

Enzymatic Treatment of Soft Jackfruit (Artocarpus heterophyllus) Pulp With Two Commercial Pectinases: Physical Properties and Viscosity Analysis

The aim of this study was to investigate the effect of enzyme hydrolysis of jackfruit pulp using two commercial pectinase enzyme solutions with different polygalacturonase activities. A 2³ factorial design, with three repetitions at the central point, was used to establish the optimal conditions of jackfruit pulp hydrolysis, evaluating the effect of time (20 - 100 min), temperature (30 - 60ºC) and enzyme concentration (0.01 - 0.09%). The dependent variables viscosity, yield, soluble solids content, color intensity, shade, and turbidity were the responses evaluated. Viscosity, color intensity, shade, and turbidity of the pulps were significantly influenced by all studied variables with the determination coefficients (R2) between 0.74 and 0.99. The lack of adjustment was not significant in the models that describe the previous properties. The highest enzyme concentration (0.09%) was the factor with the greatest influence on the studied responses, regardless of the pectinase type.

Colistimethate Acidic Hydrolysis Revisited: Arrhenius Equation Modeling Using UPLC-QToF MS.

Colistimethate (CMS), the prodrug of polymyxin E (colistin), is an antibiotic widely used as a last-line therapy against multidrug resistant Gram-negative bacteria, but little is known about its pharmacokinetics as its administration has stopped as a result of high neuro- and nephro-toxicity. The measurement of CMS levels in patients’ biological fluids is of great importance in order to find the optimal dose regimen reducing the drug toxicity. Until now, CMS assay methods are based on the indirect determination after its hydrolysis to colistin (CS). Herein, the aim is to find the optimal conditions for the complete hydrolysis of CMS to CS. The reaction was studied at accelerated conditions: 40 °C, 50 °C, and 60 °C, and the results were evaluated by assessing the Arrhenius equation and computation employing the Tenua software. A validated analytical methodology based on ultra-performance liquid chromatography (UPLC) coupled to a hybrid quadrupole time of flight (QToF) instrument is developed for the simultaneous measurement of CMS and CS. The current methodology resulted in complete hydrolysis, in contrast with the previously reported one.

Application of star point design method in enzymatic hydrolysis of paphia undulate

The effects of microwave–acid hydrolysis on enzymatic hydrolysis reaction of Paphia undulata were studied, and conditions of microwave–acid hydrolysis to prepare small molecular peptides from Paphia undulate were optimized by central composite design–response surface methodology to determine the best conditions of microwave–acid hydrolysis and enzymatic hydrolysis for this species Paphia undulata. Based on experimental results, to prepare small molecular peptides from Paphia undulate by enzymatic hydrolysis with peptide yield as the effect size, the optimal microwave-acid hydrolysis conditions are a solid-to-liquid ratio of 1:3, use of 6.4 mol/L hydrochloric acid, and microwaving at a power of 480 W for 210 s. The yield of small molecular peptide was 85.67%, which was similar to the peptide yield derived from the response surface model (86.62%).

Optimization of Jiuzao protein hydrolysis conditions and antioxidant activity in vivo of Jiuzao tetrapeptide Asp-Arg-Glu-Leu by elevating the Nrf2/Keap1-p38/PI3K-MafK signaling pathway.

Tetrapeptide Asp-Arg-Glu-Leu (DREL) was isolated from Jiuzao protein hydrolysates (JPHs) by alkaline proteinase (AP) and exhibited antioxidant activity in the HepG2 cell model in the previous study. In this study, the hydrolysis method of Jiuzao protein (JP) was further optimized by using different proteinases under different conditions (i.e., temperature, time, ratio between proteinase and substrate, and pH). Considering the limitation of in vitro assays, the AAPH-induced oxidative stress Sprague-Dawley (SD) rat model was selected to measure the antioxidant capacity of DREL in vivo. Pepsin exhibited the highest hydrolysis degree under the optimum conditions after single factor analysis (SFA) among seven proteinases. The total yield of DREL in Jiuzao was 158.24 mg kg-1Jiuzao under the pepsin's optimum hydrolysis conditions determined by response surface methodology analysis (RSMA). In addition, DREL could activate the Nrf2/Keap1-p38/PI3K-MafK signaling pathway and downstream antioxidant enzymes to improve the antioxidant ability in vivo. DREL also preliminarily exhibited anti-inflammatory activity by inhibiting the secretion of inflammatory cytokines and the mediator through the activation of Nrf2. Of note, the addition of DREL in baijiu brought an inconspicuous change in the taste after sensory evaluation. This study finds out the better proteinase used for JP hydrolysis and verifies the antioxidant capacity of DREL in vivo, which provides a potential approach to apply functional components from Jiuzao for by-product utilization. Meanwhile the antioxidant function of baijiu or other foods can be increased through adding these functional peptides without affecting the original flavor and taste in the future.

Evaluation of Plantain Biomass (&amp;lt;i&amp;gt;Musa paradisiaca&amp;lt;/i&amp;gt; L.), as Feedstock for Bio-Ethanol Production

This study investigated the viability of post-harvested plantain biomass as a promising feedstock for the production of Bioethanol. The properties of the derived bio-ethanol were determined to examine its suitability as a promising and sustainable alternative to petroleum-based ethanol The research revealed that Plantain biomass is made up of Lignocellulosic contents such as extractive, Lignin, cellulose, hemicelluloses, ash and moisture in different proportions. The different parts of the biomass such as the flower, stem and leaves were hydrolyzed using H2SO4. Optimum hydrolysis conditions of 6%w/v acid concentration, 30 min contact time and 80°C working temperature were established for Plantain stem and flower. However, hydrolysis of Plantain leaves was at the best under the experimental conditions of acid concentration (10% w/v), contact time (120 min) and temperature (120°C). The highest yield of the bio-ethanol produced was obtained from Plantain stem biomass with a record of 8.04% followed by Plantain flower with a yield of 7.73% and 757% from Plantain leaves The hydrolyzate was fermented using Baker’s yeast (Saccharomyces cerevisiae) at a room temperature of 25°C and pH of 4.5 for 4 D. The structural determination of the derived bioethanol was conducted using FT-IR analysis and the fuel properties were found to be consistent with those of the conventional ethanol. The SEM analysis conducted on the post hydrolysed biomass confirmed the effectiveness of the hydrolysis scheme adopted as evident on the surface morphology of the biomass. This study confirmed the viability of Plantain biomass as promising feedstock for Bio-ethanol production under the established hydrolysis conditions.

Study on enzymatic hydrolysis of soybean β-conglycinin using alkaline protease from Bacillus subtilis ACCC 01746 and antigenicity of its hydrolysates

Due to its beneficial health effects, the use of soybean protein has shown a continuous increase, but concerns regarding the allergenicity of soybean antigenic protein have also increased. This study aimed to evaluate the hydrolytic effects of a non-commercial alkaline protease isolated from the Bacillus subtilis ACCC 01746 on soybean β-conglycinin and the allergenicity of its hydrolysates. Alkaline protease of the strain was separated by precipitation method of organic solvents, and the β-conglycinin was separated by alkali-solution and acid-isolation and purified by use of gel column. Using the degree of hydrolysis (DH) and inhibition rate as evaluation indexes, the enzymatic hydrolysis parameters of β-conglycinin was optimized by single factor and L9(34) orthogonal tests, so as to explore the effect of the protease on the hydrolysis degree and the antigenicity of β-conglycinin hydrolysates. The results showed that the native enzyme existed as an 18.3 kDa monomer with a 430 U/g maximum activity. The purity of β-conglycinin was 84.8%. The single-factor test results showed that DH showed the oppostie trendency with the inhibition rate, and the increase of protein concentration caused monotone increasing and monotone decreasing of the inhibition rate and the DH, and the optimal protein concentration was 30 mg/mL. The optimization results showed that pH had the largest impacts on both DH and the inhibition rate, followed by enzyme dosage, hydrolysis temperature and hydrolysis time. Under the optimum hydrolysis conditions of protein concentration 30 mg/mL, enzyme dosage 0.7%, hydrolysis time 40 min, temperature 55 °C and pH 8.5, the DH reached the highest of 76.28%, and the inhibition rate was the lowest of 27.03%, which was reduced greatly compared with that before optimization. These results suggested that alkaline protease appeared to show a relatively high effeciency in lowering soybean allergenicity, making it possible to produce low-allergenicity soybean protein.

Preparation of antioxidant peptides from hairtail surimi using hydrolysis and evaluation of its antioxidant stability

In this study, antioxidant peptides were prepared from hairtail surimi by hydrolysis. Response surface methodology coupled with a Box-Behnken design was applied to optimize hydrolysis conditions. The optimum conditions were determined as: 12.1 h incubation time, 44.74 °C incubation temperature and enzyme concentration 1858.85 U/g. The amino acid compositions analysis showed most abundant amino acid in hairtail surimi antioxidant peptides (HAP) was Glutamic acid followed by Aspartic acid and Lysine. In addition, the fraction of HAP with a molecular weight less than 3 kDa showed the strongest antioxidant activity among the 4 fractions obtained by ultrafiltration. Furthermore, HAP showed good stability in mild acidic, alkaline, or salt solutions, in in vitro digestive juice, and upon heating. In conclusion, hairtail surimi might be a good source to produce antioxidant peptides, which can be used as a natural antioxidant in food industry.

Effects of Enzymatic Hydrolysis Conditions on the Antioxidant Activity of Red Tilapia (Oreochromis spp.) Viscera Hydrolysates.

Fish is an essential source of nutrients for human nutrition due to the composition of proteins, vitamins, and minerals, among other nutrients. Enzymatic hydrolysis represents an alternative for the use of by-products of the aquaculture industry. We propose to evaluate the effect of stirring speed, temperature, and initial protein concentration on the degree of hydrolysis of proteins and antioxidant activity of red tilapia (Oreochromis spp.) viscera hydrolysates. The effect of stirring speed, temperature, and initial protein concentration on the degree of hydrolysis of proteins and antioxidant activity was evaluated using an experimental design that was adjusted to a polynomial equation. The hydrolysate was fractioned to determine the antioxidant activity of the fractions, and functional properties were also measured. Stirring speed and protein concentration presented a statistically significant effect (p <0.05) on all the response variables. However, the temperature did not present a statistically significant effect on the degree of hydrolysis. The best conditions of hydrolysis were stirring speed of 51.44 rpm, a temperature of 59.15°C, and the protein concentration of 10 g L-1. The solubility of the hydrolysate protein was high at different pH, and the hydrolysate fraction with the highest antioxidant activity has a molecular weight <1 kDa. The degree of hydrolysis and the biological activity of red tilapia viscera hydrolysates (Oreochromis spp.) are affected by temperature, substrate concentration, and stirring speed. The optimal conditions of hydrolysis allowed to obtain a hydrolysate with antioxidant activity are due to the peptides with low molecular weight.

Optimizing of Enzyme Hydrolysis Condition for Bitterness Suppression of Soybean Protein Using Response Surface Methodology (RSM)

Enzyme hydrolysis of soybean protein can be adjusted according to purposes, but should be optimized for reaction time, concentration and substrate conditions to prevent bitterness caused by excessive hydrolysis. This study was carried out to find the optimal condition of the soybean protein hydrolysis process using a response surface methodology. The experiment was designed based on a central composite design, and the independent variables were the soybean protein extraction pH (X1, 10-12), enzyme concentration (X2, 0.1-0.5%) and hydrolysis time (X3, 150-210 minutes). The results of the degree of hydrolysis (Y1), pH (Y2) and soluble solid contents (Y3) were fitted to a response surface methodology model (R2= 0.91, 0.98, and 0.86, respectively). The optimal hydrolysis condition for soybean protein hydrolysis was as follows; pH 12, enzyme concentration 0.27% and 187.88 min, respectively. While richness and sourness were increased with soybean protein hydrolysis, the saltiness was decreased. The bitterness of the hydrolysate prepared at the optimal condition did not show any difference compared with that of the soybean protein, whereas richness and sourness showed a significant increase. The enzyme hydrolysate at the optimal condition showed distribution of a molecular weight lower than the soybean protein did to form intense bands at 35, and 25 kDa. Therefore, this hydrolysate was expected to be used as a high-value plant protein food material.

Evolutionary engineering of Lactobacillus bulgaricus reduces enzyme usage and enhances conversion of lignocellulosics to D-lactic acid by simultaneous saccharification and fermentation

BackgroundSimultaneous saccharification and fermentation (SSF) of pre-treated lignocellulosics to biofuels and other platform chemicals has long been a promising alternative to separate hydrolysis and fermentation processes. However, the disparity between the optimum conditions (temperature, pH) for fermentation and enzyme hydrolysis leads to execution of the SSF process at sub-optimal conditions, which can affect the rate of hydrolysis and cellulose conversion. The fermentation conditions could be synchronized with hydrolysis optima by carrying out the SSF at a higher temperature, but this would require a thermo-tolerant organism. Economically viable production of platform chemicals from lignocellulosic biomass (LCB) has long been stymied because of the significantly higher cost of hydrolytic enzymes. The major objective of this work is to develop an SSF strategy for D-lactic acid (D-LA) production by a thermo-tolerant organism, in which the enzyme loading could significantly be reduced without compromising on the overall conversion.ResultsA thermo-tolerant strain of Lactobacillus bulgaricus was developed by adaptive laboratory evolution (ALE) which enabled the SSF to be performed at 45 °C with reduced enzyme usage. Despite the reduction of enzyme loading from 15 Filter Paper Unit/gLCB (FPU/gLCB) to 5 FPU/gLCB, we could still achieve ~ 8% higher cellulose to D-LA conversion in batch SSF, in comparison to the conversion by separate enzymatic hydrolysis and fermentation processes at 45 °C and pH 5.5. Extending the batch SSF to SSF with pulse-feeding of 5% pre-treated biomass and 5 FPU/gLCB, at 12-h intervals (36th–96th h), resulted in a titer of 108 g/L D-LA and 60% conversion of cellulose to D-LA. This is one among the highest reported D-LA titers achieved from LCB.ConclusionsWe have demonstrated that the SSF strategy, in conjunction with evolutionary engineering, could drastically reduce enzyme requirement and be the way forward for economical production of platform chemicals from lignocellulosics. We have shown that fed-batch SSF processes, designed with multiple pulse-feedings of the pre-treated biomass and enzyme, can be an effective way of enhancing the product concentrations.

반응표면분석법을 이용한 천년초 줄기로부터 식이섬유소 추출을 위한 효소처리 조건의 최적화

This study aimed to optimize the hydrolysis conditions required for extraction of dietary fiber from Opuntia humifusa stem using Viscozyme® (MilliporeSigma, St. Louis, MO, USA) with response surface methodology (RSM). A central composite design was applied to examine the effects of the independent variables, enzyme concentration (0.5-2.5%, X1) and reaction time (1-5h, X2). The hydrolysis conditions were optimized using total yield, total dietary fiber (TDF), water-soluble dietary fiber (SDF), and water-insoluble dietary fiber (IDF) contents of hydrolysates as dependent variables. The total yield was 39.9-53.2% and the coefficient (R2) of the derived equation from the response surface regression for total yield was 0.9073. The TDF and SDF contents in all hydrolysates were 29.02-43.82% and 27.25-40.68%, respectively, which were within the 1% level. The IDF contents in all hydrolysates were 0.98-3.80% (R2 0.8886) and with in 5% significance. The optimal hydrolysis conditions comprised 1.0-1.8% Viscozyme® and an incubation period of 1.0-1.8 h. Our results suggested that O. humifusa could be a source that might extend the application of dietary fiber in functional food industries.