ABSTRACT
Lipase from Rhizopus oryzae (ROL) exhibits remarkable sn-1,3 stereoselectivity and catalytic activity, but its poor thermostability limits its applications in the production of 1,3-dioleoyl-2-palmitoyl glycerol (OPO, a high-quality substitute for human milk fat). In this work, a semirational method was proposed to engineer the thermostability and catalytic activity of 4M (ROL mutant in our previous study). First, a computer-aided design is performed using 4M as a template, and N-glycosylation mutants are then recombinantly expressed and screened in Pichia pastoris, the optimal mutant N227 exhibited a half-life of 298.8 h at 45 °C, which is 7.23-folds longer than that of 4M. Its catalytic activity also reached 1043.80 ± 61.98 U/mg, representing a 29.2% increase compared to 4M (808.02 ± 47.02 U/mg). Molecular dynamics simulations of N227 suggested that the introduction of glycan enhanced the protein rigidity, while the strong hydrogen bonds formed between the glycan and the protein stabilized the lipase structure, thereby improving its thermostability. The acidolysis reaction between oleic acid (OA) and glycerol tripalmitate (PPP) was successfully carried out using immobilized N227, achieving a molar conversion rate of 90.2% for PPP. This engineering strategy guides the modification of lipases, while the glycomutants obtained in this study have potential applications in the biosynthesis of OPO.
Subject(s)
Biocatalysis , Enzyme Stability , Fungal Proteins , Lipase , Rhizopus oryzae , Lipase/chemistry , Lipase/genetics , Lipase/metabolism , Glycosylation , Fungal Proteins/genetics , Fungal Proteins/chemistry , Fungal Proteins/metabolism , Rhizopus oryzae/enzymology , Rhizopus oryzae/genetics , Rhizopus oryzae/chemistry , Rhizopus oryzae/metabolism , Hot Temperature , Kinetics , Rhizopus/enzymology , Rhizopus/geneticsABSTRACT
This study investigates the use of nanodiamonds (ND) as a promising carrier for enzyme immobilization and compares the effectiveness of immobilized and native enzymes. Three different enzyme types were tested, of which Rhizopus niveus lipase (RNL) exhibited the highest relative activity, up to 350â¯%. Under optimized conditions (1â¯h, pHâ¯7.0, 40⯰C), the immobilized ND-RNL showed a maximum specific activity of 0.765â¯Uâ¯mg-1, significantly higher than native RNL (0.505â¯Uâ¯mg-1). This study highlights a notable enhancement in immobilized lipase; furthermore, the enzyme can be recycled in the presence of a natural deep eutectic solvent (NADES), retaining 76â¯% of its initial activity. This aids in preserving the native conformation of the protein throughout the reusability process. A test on brine shrimp revealed that even at low concentrations, ND-RNL had minimal toxicity, indicating its low cytotoxicity. The in silico molecular dynamics simulations performed in this study offer valuable insights into the mechanism of interactions between RNL and ND, demonstrating that RNL immobilization onto NDs enhances its efficiency and stability. All told, these findings highlight the immense potential of ND-immobilized RNL as an excellent candidate for biological applications and showcase the promise of further research in this field.
Subject(s)
Deep Eutectic Solvents , Enzymes, Immobilized , Lipase , Nanodiamonds , Lipase/chemistry , Lipase/metabolism , Enzymes, Immobilized/chemistry , Enzymes, Immobilized/metabolism , Nanodiamonds/chemistry , Deep Eutectic Solvents/chemistry , Molecular Dynamics Simulation , Enzyme Stability , Animals , Hydrogen-Ion Concentration , Rhizopus/enzymology , Temperature , Artemia/drug effects , Solvents/chemistryABSTRACT
BACKGROUND: Solid-state fermentation (SSF) has been widely used in the processing of sorghum grain (SG) because it can produce products with improved sensory characteristics. To clarify the influence of different microbial strains on the SSF of SG, especially on the polyphenols content and composition, Lactiplantibacillus plantarum, Saccharomyces cerevisiae, Rhizopus oryzae, Aspergillus oryzae, and Neurospora sitophila were used separately and together for SSF of SG. Furthermore, the relationship between the dynamic changes in polyphenols and enzyme activity closely related to the metabolism of polyphenols has also been measured and analyzed. Microstructural changes observed after SSF provide a visual representation of the SSF on the SG. RESULTS: After SSF, tannin content (TC) and free phenolic content (FPC) were decreased by 56.36% and 23.48%, respectively. Polyphenol oxidase, ß-glucosidase and cellulase activities were increased 5.25, 3.27, and 45.57 times, respectively. TC and FPC were negatively correlated with cellulase activity. A positive correlation between FPC and xylanase activity after 30 h SSF became negative after 48 h SSF. The SG surface was fragmented and porous, reducing the blocking effect of cortex. CONCLUSION: Cellulase played a crucial role in promoting the degradation of tannin (antinutrient) and phenolic compounds. Xylanase continued to release flavonoids while microbial metabolism consumed them with the extension of SSF time. SSF is an effective way to improve the bioactivity and processing characteristics of SG. © 2024 Society of Chemical Industry.
Subject(s)
Catechol Oxidase , Fermentation , Polyphenols , Saccharomyces cerevisiae , Sorghum , Sorghum/chemistry , Sorghum/metabolism , Polyphenols/metabolism , Polyphenols/chemistry , Saccharomyces cerevisiae/metabolism , Saccharomyces cerevisiae/chemistry , Catechol Oxidase/metabolism , Rhizopus/metabolism , Rhizopus/enzymology , Tannins/metabolism , Tannins/analysis , Tannins/chemistry , Aspergillus oryzae/metabolism , Aspergillus oryzae/enzymology , Cellulase/metabolism , Cellulase/chemistry , Neurospora/metabolism , Food Handling/methods , beta-Glucosidase/metabolism , Seeds/chemistry , Seeds/metabolism , Seeds/microbiology , Bacteria/metabolism , Bacteria/classification , Bacteria/enzymology , Bacteria/isolation & purification , Phenols/metabolism , Phenols/chemistry , Phenols/analysisABSTRACT
OBJECTIVES: Cold-active lipases which show high specific activity at low temperatures are attractive in industrial applications in terms of product stability and energy saving. We aimed to identify novel cold-active lipase suitable for oleates synthesis and bread making. RESULTS: A novel lipase gene (RmLipA) from Rhizopus microsporus was cloned and heterologously expressed in Pichia pastoris. The encoding sequence displayed 75% identity to the lipase from R. niveus. The highest extracellular lipase activity of 7931 U/mL was achieved in a 5-L fermentation. The recombinant enzyme (RmLipA) was optimally active at pH 8.0 and 20-25 °C, respectively, and stable over a wide pH range of 2.0-11.0. The enzyme was a cold-active lipase, exhibiting > 80% of its maximal activity at 0 °C. RmLipA was a sn-1,3 regioselective lipase, and preferred to hydrolyze pNP esters and triglycerides with relatively long chain fatty acids. RmLipA synthesized various oleates using oleic acid and different alcohols as substrates (> 95%). Moreover, it significantly improved the quality of bread by increasing its specific volume (21.7%) and decreasing its crumb firmness (28.6%). CONCLUSIONS: A novel cold-active lipase gene from R. microsporus was identified, and its application potentials were evaluated. RmLipA should be a potential candidate in oleates synthesis and bread making industries.
Subject(s)
Lipase/metabolism , Oleic Acid/metabolism , Rhizopus/enzymology , Saccharomycetales/growth & development , Batch Cell Culture Techniques , Bread/analysis , Cloning, Molecular , Cold Temperature , Enzyme Activation , Fermentation , Fungal Proteins/genetics , Fungal Proteins/metabolism , Hydrogen-Ion Concentration , Lipase/genetics , Rhizopus/genetics , Saccharomycetales/geneticsABSTRACT
Cellulose microcrystalline (MCC) was widely used in pharmaceutical and chemical industries because of its low degree of polymerization and large specific surface area. As its modified form, dialdehyde cellulose (DAC) was used for cross-linking and immobilizing Rhizopus lipase together with magnetic nanoparticles (MNPs) due to its active aldehyde groups. In this study, in order to maintain the original enzyme activity as much as possible and improve the stability of lipase, the Rhizopus lipase was successfully immobilized on the magnetic dialdehyde cellulose nanoparticles (MDC). Specifically, the immobilization conditions including dosage of DAC, concentration of enzyme, immobilization time and temperature together with pH value of the reaction medium were optimized. Maximum immobilization yield (60.03 ± 0.49%) and recovery activity (88.88 ± 0.61%) can be obtained under the optimal process conditions. The changes in secondary structures of immobilized enzyme revealed the increment in conformational rigidity, which can be reflected in temperature and pH stability as well as tolerance of organic reagents. Additionally, the recovery activity of immobilized enzyme still reached 50.60 ± 0.59% after 30 d of storage and 52.10 ± 0.57% retained after 6 cycles. These results indicated the ideal application prospect of MDC in immobilized enzymes.
Subject(s)
Cellulose/analogs & derivatives , Lipase/chemistry , Magnetite Nanoparticles/chemistry , Rhizopus/enzymology , Cellulose/chemistry , Enzyme Stability , Enzymes, Immobilized/chemistry , Fungal Proteins/chemistry , Hydrogen-Ion Concentration , Protein Structure, Secondary , Temperature , TimeABSTRACT
The catalytic mechanism of most lipases involves a step called "interfacial activation" which significantly increases lipases activity beyond the critical micellar concentration (CMC) of substrate. In the present study, Rhizopus chinensis lipase (RCL) was used as a research model to explore the mechanism of lipase interfacial activation beyond the CMC. Molecular dynamic (MD) simulations indicated the open- and closed-lid transitions and revealed that Phe113 was the critical site for RCL activation by its dynamic flipping. Such putative switch affecting interfacial activation has not been reported in lipase so far. The function of Phe113 was subsequently verified by mutation experiments. The F113W mutant increases the lipase catalytic efficiency (1.9 s-1·µM-1) to 280% at the optimum temperature (40 °C) and pH 8.5 with the addition of 0.12 µg protein in the 200 µL reaction system. MD simulations indicated that the fast flipping rate from the closed to the open state, the high open state proportion, and the exposure of the catalytic triad are the main reasons for the lipase activation. The mutual corroboration of simulations and site-directed mutagenesis results revealed the vital role of Phe113 in the lipase activation.
Subject(s)
Butyrates/chemistry , Fungal Proteins/chemistry , Lipase/chemistry , Phenylalanine/chemistry , Rhizopus/chemistry , Binding Sites , Biocatalysis , Butyrates/metabolism , Cloning, Molecular , Escherichia coli/genetics , Escherichia coli/metabolism , Fungal Proteins/genetics , Fungal Proteins/metabolism , Gene Expression , Genetic Vectors/chemistry , Genetic Vectors/metabolism , Hydrogen-Ion Concentration , Kinetics , Lipase/genetics , Lipase/metabolism , Molecular Dynamics Simulation , Phenylalanine/metabolism , Protein Binding , Protein Conformation, alpha-Helical , Protein Conformation, beta-Strand , Protein Interaction Domains and Motifs , Recombinant Proteins/chemistry , Recombinant Proteins/genetics , Recombinant Proteins/metabolism , Rhizopus/enzymology , Substrate Specificity , Temperature , Thermodynamics , Water/chemistryABSTRACT
To improve the thermostability of r27RCL from Rhizopus chinensis and broaden its industrial applications, we used rational design (FoldX) according to ΔΔG calculation to predict mutations. Four thermostable variants S142A, D217V, Q239F, and S250Y were screened out and then combined together to generate a quadruple-mutation (S142A/D217V/Q239F/S250Y) variant, called m31. m31 exhibited enhanced thermostability with a 41.7-fold longer half-life at 60 °C, a 5 °C higher of topt, and 15.8 °C higher of T5030 compared to that of r27RCL expressed in Pichiapastoris. Molecular dynamics simulations were conducted to analyze the mechanism of the thermostable mutant. The results indicated that the rigidity of m31 was improved due to the decreased solvent accessible surface area, a newly formed salt bridge of Glu292:His171, and the increased ΔΔG of m31. According to the root-mean-square-fluctuation analysis, three positive mutations S142A, D217V, and Q239F located in the thermal weak regions and greatly decreased the distribution of thermal-fluctuated regions of m31, compared to that of r27RCL. These results suggested that to simultaneously implement MD simulations and ΔΔG-based rational approaches will be more accurate and efficient for the improvement of enzyme thermostability.
Subject(s)
Fungal Proteins/chemistry , Hot Temperature , Lipase/chemistry , Molecular Dynamics Simulation , Protein Denaturation , Rhizopus/enzymology , Amino Acid Substitution , Enzyme Stability , Fungal Proteins/genetics , Lipase/geneticsABSTRACT
To produce manno-oligosaccharides from cassia gum, a mutated glycoside hydrolase family 134 ß-mannanase gene (mRmMan134A) from Rhizopus microsporus var. rhizopodiformis F518 was expressed in Pichia pastoris and a high expression level (3680â¯Uâ¯mL-1) was obtained through high cell density fermentation. mRmMan134A exhibited maximum activity at pH 5.5 and 50⯰C. It was then subjected to hydrolyze cassia gum with 70.6% of overall yield of manno-oligosaccharides. From the hydrolysate, seven components (F1-F7) were separated and identified as mannose, mannobiose, galactose, mannotriose, mannotetraose, 61-α-d-galactosyl-ß-d-mannobiose, and mannopentaose, respectively. According to in vitro fermentation, the manno-oligosaccharides were able to promote the growth of three Bifidobacterium strains and six Lactobaillus strains with 3.0-fold increment in culture absorbance, and these strains preferred manno-oligosaccharides with degree of polymerization (DP) 2-3 rather than those with DP 4-5. Novel manno-oligosaccharides from cassia gum with promising prebiotic activity were provided in the present study.
Subject(s)
Cassia/metabolism , Oligosaccharides/metabolism , Prebiotics , beta-Mannosidase/metabolism , Batch Cell Culture Techniques , Bifidobacterium/drug effects , Bifidobacterium/growth & development , Hydrogen-Ion Concentration , Hydrolysis , Mannose/metabolism , Oligosaccharides/isolation & purification , Oligosaccharides/pharmacology , Rhizopus/enzymology , Temperature , beta-Mannosidase/geneticsABSTRACT
Traditionally, chymosin has been used for milk-clotting, but this naturally occurring enzyme is in short supply and its use has raised religious and ethical concerns. Because milk-clotting peptidases are a promising substitute for chymosin in cheese preparation, there is a need to find and test the specificity of these enzymes. Here, we evaluated the milk-clotting properties of an aspartic peptidase secreted by Rhizopus microsporus. The molecular mass of this enzyme was estimated at 36 kDa and Pepstatin A was determined to be an inhibitor. Optimal activity occurred at a pH of 5.5 and a temperature range of 50-60 °C, but the peptidase was stable in the pH range of 4-7 and a temperature as low as 45 °C. Proteolytic activity was significantly reduced in the presence of Cu2+ and Al3+. When enzyme substrates based on FRET were used, this peptidase exhibited the highest catalytic efficiency for Abz-KNRSSKQ-EDDnp (4,644 ± 155 mM-1.s-1), Abz-KLRSSNQ-EDDnp (3,514 ± 130 mM-1.s-1), and Abz-KLRQSKQ-EDDnp (3,068 ± 386 mM-1.s-1). This study presents a promising peptidase for use in cheese making, due to its high stability in the presence of Ca2+ and broad pH range of 4-7, in addition to its ability to efficiently clot milk.
Subject(s)
Aspartic Acid Proteases/chemistry , Fungal Proteins/chemistry , Milk/chemistry , Rhizopus/enzymology , Animals , Cattle , Hydrogen-Ion ConcentrationABSTRACT
An in situ and real-time investigation was performed using an optical cell system and in-silico analysis to reveal the impacts of pressure and temperature on the conformational state and behaviours of Rhizopus chinensis lipase (RCL). The fluorescence intensity (FI) of RCL increased remarkably under high pressure, and part of this increase was recovered after depressurization. This result displayed the partially reversible conformational change of RCL, which may be associated with the local change of Trp224 near the catalytic centre. High temperature caused a significant loss of secondary structure, whereas the α-helical segments including the lid were preserved by high pressure even at temperatures over 60 °C. The parameters of enzymatic reaction monitored by UV showed that the hydrolysis rate was remarkably enhanced by the pressure of 200 MPa. In the pressure range of 0.1-200 MPa, the active volume measured by the in situ system decreased from -2.85 to -6.73 mL/mol with the temperature increasing from 20 °C to 40 °C. The high catalytic capacity of the lipase under high pressure and high temperature was primarily attributed to pressure protection on RCL.
Subject(s)
Lipase/chemistry , Lipase/metabolism , Pressure , Rhizopus/enzymology , Temperature , Biocatalysis , Computer Simulation , Kinetics , Models, Molecular , Protein ConformationABSTRACT
Lipases are among the most frequently used biocatalysts in organic synthesis, allowing numerous environmentally friendly and inexpensive chemical transformations. Here, we present a biomimetic strategy based on iron(III)-catalyzed oxidative coupling and selective ester monohydrolysis using lipases for the synthesis of unsymmetric biphenyl-based esters under mild conditions. The diverse class of biphenyl esters is of pharmaceutical and technical relevance. We explored the potency of a series of nine different lipases of bacterial, fungal, and mammalian origin on their catalytic activities to cleave biphenyl esters, and optimized the reaction conditions, in terms of reaction time, temperature, pH, organic solvent, and water-organic solvent ratios, to improve the chemoselectivity, and hence control the ratio of unsymmetric versus symmetric products. Elevated temperature and increased DMSO content led to an almost exclusive monohydrolysis by the four lipases Candida rugosa lipase (CRL), Mucor miehei lipase (MML), Rhizopus niveus lipase (RNL), and Pseudomonas fluorescens lipase (PFL). The study was complemented by in silico binding predictions to rationalize the observed differences in efficacies of the lipases to convert biphenyl esters. The optimized reaction conditions were transferred to the preparative scale with high yields, underlining the potential of the presented biomimetic approach as an alternative strategy to the commonly used transition metal-based strategies for the synthesis of diverse biphenyl esters.
Subject(s)
Candida/enzymology , Esters/chemistry , Lipase/metabolism , Mucor/enzymology , Pseudomonas fluorescens/enzymology , Rhizopus/enzymology , Bacterial Proteins/metabolism , Biological Mimicry , Catalysis , Computer Simulation , Fungal Proteins/metabolism , Hydrogen-Ion Concentration , Hydrolysis , TemperatureABSTRACT
Microorganisms have evolved to produce specific end products for many reasons, including maintaining redox balance between NAD+ and NADH. The yeast Saccharomyces cerevisiae, for example, produces ethanol as a primary end product from glucose for the regeneration of NAD+. Engineered S. cerevisiae strains have been developed to ferment lignocellulosic sugars, such as xylose, to produce lactic acid by expression of a heterologous lactate dehydrogenase (ldhA from Rhizopus oryzae) without genetic perturbation to the native ethanol pathway. Surprisingly, the engineered yeast strains predominantly produce ethanol from glucose, but produce lactic acid as the major product from xylose. Here, we provide initial evidence that the shift in product formation from ethanol to lactic acid during xylose fermentation is at least partially dependent on the presence of functioning monocarboxylate transporter genes/proteins, including JEN1 and ADY2, which are downregulated and unstable in the presence of glucose, but upregulated/stable on xylose. Future yeast metabolic engineering studies may find the feedstock/carbon selection, such as xylose, an important step toward improving the yield of target end products.
Subject(s)
L-Lactate Dehydrogenase/metabolism , Lactic Acid/metabolism , Membrane Transport Proteins/genetics , Metabolic Engineering , Rhizopus/enzymology , Saccharomyces cerevisiae Proteins/genetics , Saccharomyces cerevisiae/metabolism , Xylose/metabolism , Down-Regulation , Ethanol/metabolism , Fermentation , Fungal Proteins/genetics , Fungal Proteins/metabolism , Gene Expression , Glucose/metabolism , L-Lactate Dehydrogenase/genetics , Monocarboxylic Acid Transporters/genetics , Rhizopus/genetics , Saccharomyces cerevisiae/genetics , Sequence Deletion , Symporters/genetics , TransgenesABSTRACT
The possibility of improving brain function coupled with its preferential uptake in the brain has garnered attention for docosahexaenoic acid-bound lysophosphatidylcholine (DHA-LPC). However, studies focusing on the health benefits of dietary DHA-LPC are lacking. We prepared a dietary oil rich in DHA-LPC (DHA-LPC rich oil) via enzymatic modification of phospholipids (PL) extracted from squid (Todarodes pacificus) meal and purification of active carbon, ion exchange resin, and silica gel. We then examined the effects of dietary DHA-LPC rich oil on male Wistar rats by evaluating serum and liver lipid profiles, fatty acid (FA) metabolizing enzyme activity, and the FA composition of serum and brain. The rats were fed a basal diet containing either soybean oil alone (7%) or soybean oil (4.5%) with DHA-LPC rich oil (2.5%) for 28 days, and then evaluated. The rats fed the diet containing DHA-LPC rich oil showed reduced triacylglycerol concentration due, in part, to the enhancement of carnitine palmitoyltransferase 2 and acyl-CoA oxidase activities and suppression of acetyl-CoA carboxylase and glucose-6-phosphate dehydrogenase activities in the liver. Moreover, the dietary DHA-LPC rich oil moderately increased DHA in the FA composition of the rat hippocampus, which may be due to elevated DHA composition in serum LPC. These results suggest that DHA-LPC rich oil has hypolipidemic effect and moderate increase in hippocampal DHA amount in normal rats.
Subject(s)
Brain/metabolism , Dietary Fats, Unsaturated/pharmacology , Docosahexaenoic Acids/pharmacology , Hypolipidemic Agents/pharmacology , Liver/metabolism , Lysophosphatidylcholines/pharmacology , Administration, Oral , Animals , Brain Chemistry , Carboxylic Ester Hydrolases/chemistry , Decapodiformes/chemistry , Dietary Fats, Unsaturated/administration & dosage , Docosahexaenoic Acids/administration & dosage , Hippocampus/chemistry , Hippocampus/metabolism , Hypolipidemic Agents/administration & dosage , Liver/chemistry , Lysophosphatidylcholines/administration & dosage , Male , Phospholipids/chemistry , Phospholipids/isolation & purification , Rats, Wistar , Rhizopus/enzymologyABSTRACT
Members of an important group of industrial enzymes, Rhizopus lipases, exhibit valuable hydrolytic features that underlie their biological functions. Particularly important is their N-terminal polypeptide segment (NTPS), which is required for secretion and proper folding but is removed in the process of enzyme maturation. A second common feature of this class of lipases is the α-helical "lid", which regulates the accessibility of the substrate to the enzyme active site. Some Rhizopus lipases also exhibit "interfacial activation" by micelle and/or aggregate surfaces. While it has long been recognized that the NTPS is critical for function, its dynamic features have frustrated efforts to characterize its structure by X-ray crystallography. Here, we combine nuclear magnetic resonance spectroscopy and X-ray crystallography to determine the structure and dynamics of Rhizopus chinensis lipase (RCL) with its 27-residue NTPS prosequence (r27RCL). Both r27RCL and the truncated mature form of RCL (mRCL) exhibit biphasic interfacial activation kinetics with p-nitrophenyl butyrate (pNPB). r27RCL exhibits a substrate binding affinity significantly lower than that of mRCL due to stabilization of the closed lid conformation by the NTPS. In contrast to previous predictions, the NTPS does not enhance lipase activity by increasing surface hydrophobicity but rather inhibits activity by forming conserved interactions with both the closed lid and the core protein structure. Single-site mutations and kinetic studies were used to confirm that the NTPS serves as internal competitive inhibitor and to develop a model of the associated process of interfacial activation. These structure-function studies provide the basis for engineering RCL lipases with enhanced catalytic activities.
Subject(s)
Fungal Proteins/chemistry , Industrial Microbiology , Lipase/chemistry , Peptides/chemistry , Rhizopus/enzymology , Amino Acid Sequence , Crystallography, X-Ray , Fungal Proteins/genetics , Fungal Proteins/metabolism , Hydrolysis , Kinetics , Lipase/genetics , Lipase/metabolism , Nuclear Magnetic Resonance, Biomolecular , Peptides/genetics , Peptides/metabolism , Structure-Activity Relationship , Substrate SpecificityABSTRACT
Cheese production is projected to reach 20 million metric tons by 2020, of which 33% is being produced using calf rennet (EC 3.4.23.4). There is shortage of calf rennet, and use of plant and microbial rennets, hydrolyze milk proteins non-specifically resulting in low curd yields. This study reports fungal enzymes obtained from cost effective medium, with minimal down streaming, whose activity is comparable with calf and Mucor rennet. Of the fifteen fungi that were screened, Mucor thermohyalospora (MTCC 1384) and Rhizopus azygosporus (MTCC 10195) exhibited the highest milk-clotting activity (MCA) of 18,383 ± 486 U/ml and 16,373 ± 558 U/ml, respectively. Optimization exhibited a 33% increase in enzyme production (30 g wheat bran containing 6% defatted soy meal at 30 °C, pH 7) for M. thermohyalospora. The enzyme was active from pH 5-10 and temperature 45-55 °C. Rhizopus azygosporus exhibited 31% increase in enzyme production (30 g wheat bran containing 4% defatted soy meal at 30 °C, pH 6) and the enzyme was active from pH 6-9 at 50 °C. Curd yields prepared from fungal enzyme extract decreased (5-9%), when compared with calf rennet and Mucor rennet. This study describes the potential of fungal enzymes, hitherto unreported, as a viable alternative to calf rennet.
Subject(s)
Aspartic Acid Endopeptidases/metabolism , Mucor/enzymology , Rhizopus/enzymology , Fermentation , Hydrogen-Ion Concentration , Industrial Microbiology/methods , Mucor/metabolism , Rhizopus/metabolism , Substrate Specificity , TemperatureABSTRACT
Dialdehyde starch (DAS) is a kind of modified starch which contains many active aldehyde groups and has good biocompatibility. In this study, magnetic dialdehyde starch nanoparticles were successfully used to immobilize lipase. The lipase was immobilized onto magnetic nanoparticles by using DAS instead of glutaraldehyde as a crosslinker. The parameters like DAS dosage, enzyme concentration and immobilization time were optimized. Enzymatic properties studies exhibited that after DAS cross-linking, the storage stability of the immobilized enzyme reached 82.5%, and the recycling rate reached 53.6%, whereas in case of glutaraldehyde cross linker, it was 79.4% and 46.8%, the former also exhibited better stability and durability. Compared with the free enzyme, the immobilized enzyme indicated higher acid-base tolerance and thermal stability, and had good enzymatic properties. Magnetic dialdehyde starch nanoparticles may have application prospects as an excellent enzyme carrier, which provides a reference for the preparation of other immobilized enzymes with excellent performance.
Subject(s)
Carboxylic Ester Hydrolases/chemistry , Cross-Linking Reagents/chemistry , Enzymes, Immobilized/chemistry , Magnetite Nanoparticles/chemistry , Starch/analogs & derivatives , Enzyme Assays , Enzyme Stability , Hydrogen-Ion Concentration , Oxidation-Reduction , Periodic Acid/chemistry , Rhizopus/enzymology , Starch/chemistry , TemperatureABSTRACT
The production of membrane-associated lipase from Rhizopus chinensis (RCL), which has a high ester synthesis activity and important potential applications, is difficult in heterologous expression system such as Escherichia coli and often leads to the formation of inclusion bodies. Here, we describe the soluble expression of mature RCL (mRCL) using maltose-binding protein (MBP) as a solubility-enhancing tag in the E. coli system. Although the MBP-mRCL fusion protein was soluble, mRCL was insoluble after removal of the MBP tag in E. coli BL21 (DE3). Using E. coli BL21 trxB (DE3) as an expression host, soluble mRCL was obtained and expression conditions were optimized. Furthermore, the ester synthesis activity of soluble mRCL was increased by detergent treatment and was found to be 3.5 and 1.5 times higher than those of the untreated enzyme and naturally occurring enzyme, respectively. Overall, this study provides a potential approach for producing active and soluble forms of eukaryotic lipases in a heterologous E. coli expression system.
Subject(s)
Lipase/biosynthesis , Rhizopus/enzymology , Cloning, Molecular , Culture Media , Escherichia coli , Esters/metabolism , Lipase/genetics , Lipase/isolation & purification , Maltose-Binding Proteins/genetics , Recombinant Fusion Proteins/metabolism , Rhizopus/geneticsABSTRACT
Evolution of Rhizopus oryzae and Trichoderma reesei biomass in rice bran, their enzyme activity, and the profile of phenolic compounds released from the lignocellulosic matrices were determined and correlated by principal component analysis (PCA). PCA analysis confirms that cultivation of rice bran affected the release of methanol-soluble phenolic compounds (MSPC), ethanol-soluble phenolic compounds (ESPC), and bound phenolic compounds (BPC) positively, due to their enzymatic activity. The release of MSPC was influenced by the activity of cellulase and endoglucanase, which increased 110.6% and 136.3%, respectively, for Rhizopus oryzae and Trichoderma reesei. Gallic acid was the main component in the MSPC and ESPC compound fractions. Ferulic and syringic acids were found in its bound (BPC) form in the biomass. This study showed that bioactive compounds be released from lignocellulosic materials by fungus action and this process can be conducted to obtain specific phenolic compounds. PRACTICAL APPLICATION: Due the demand by natural compounds with biological activity, such as phenolic compounds, it is interesting to purpose alternatives to enhance their yield, like for instance, by fungal fermentation of lignocellulosic material. Therefore, understanding the relations among different phenolic compounds released and the production of fungal hydrolases during growth of Rhizopus oryzae and Trichoderma reesei in solid state cultivation using rice bran as a substrate is fundamental to control the process. This knowledge gets viable scale up to apply the phenolic compounds as preservative in food chain, because this becomes possible directing the process to obtain specific bioactive compounds in less time of cultivation and with low cost.
Subject(s)
Cellulase/metabolism , Oryza/chemistry , Phenols/analysis , Rhizopus/enzymology , Trichoderma/enzymology , Biomass , Cellulose/metabolism , Coumaric Acids/analysis , Culture Media , Fermentation , Gallic Acid/analogs & derivatives , Gallic Acid/analysis , Rhizopus/growth & development , Trichoderma/growth & developmentABSTRACT
A far-red fluorescent probe has been developed for sensing fungal laccase. The probe was used to determine that Rhizopus oryzae had a high level endogenous laccase amongst 24 fungal strains. The Rhizopus oryzae was then used as a biocatalyst for the preparation of dicoumarin resulting in significant inhibition of Mycobacterium tuberculosis H37Ra.
Subject(s)
Antitubercular Agents/pharmacology , Biocatalysis , Dicumarol/pharmacology , Fluorescent Dyes/chemistry , Laccase/analysis , Laccase/metabolism , Mycobacterium tuberculosis/drug effects , Rhizopus/enzymology , Antitubercular Agents/chemistry , Antitubercular Agents/metabolism , Dicumarol/chemistry , Dicumarol/metabolism , Microbial Sensitivity Tests , Microscopy, Confocal , Molecular Structure , Optical ImagingABSTRACT
Lipase r27RCL from Rhizopus chinensis was immobilized onto octyl-modified mesocellular foams (MCFs-C8) via two-step process of enzyme adsorption and cross-linking. Oxidized gum arabic was used as substitute for harmful glutaraldehyde to improve catalytic performance of immobilized enzyme for catalysis in non-aqueous phase. The parameters like aldehyde concentration, cross-linking time were optimized. Cross-linked enzyme aggregates (CLEAs) of lipase r27RCL prepared in MCFs-C8 by using oxidized gum arabic (GA-CLEAs@MCFs-C8) showed the highest esterification activity (145⯵molâ¯min-1â¯mg-1 protein) compared with lipase adsorbed onto MCFs-C8 (MCFs-C8-r27RCL) (98⯵molâ¯min-1â¯mg-1 protein), CLEAs of lipase in MCFs-C8 by glutaraldehyde (G-CLEAs@MCFs-C8) (88⯵molâ¯min-1â¯mg-1 protein) and immobilized lipase onto octyl/epoxy (1,1, v/v) modified MCFs (MCFs-octyl-epoxy-r27RCL) (35⯵molâ¯min-1â¯mg-1 protein). Moreover, GA-CLEAs@MCFs-C8 exhibited excellent thermal and mechanical stability, and could still maintain 69% of initial activity after 5 time cycles.