26
|
Xu G, Zha J, Cheng H, Ibrahim MHA, Yang F, Dalton H, Cao R, Zhu Y, Fang J, Chi K, Zheng P, Zhang X, Shi J, Xu Z, Gross RA, Koffas MAG. Engineering Corynebacterium glutamicum for the de novo biosynthesis of tailored poly-γ-glutamic acid. Metab Eng 2019; 56:39-49. [PMID: 31449877 DOI: 10.1016/j.ymben.2019.08.011] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 08/15/2019] [Accepted: 08/17/2019] [Indexed: 11/17/2022]
Abstract
γ-Polyglutamic acid (γ-PGA) is a biodegradable polymer naturally produced by Bacillus spp. that has wide applications. Fermentation of γ-PGA using Bacillus species often requires the supplementation of L-glutamic acid, which greatly increases the overall cost. Here, we report a metabolically engineered Corynebacterium glutamicum capable of producing γ-PGA from glucose. The genes encoding γ-PGA synthase complex from B. subtilis (pgsB, C, and A) or B. licheniformis (capB, C, and A) were expressed under inducible promoter Ptac in a L-glutamic acid producer C. glutamicum ATCC 13032, which led to low levels of γ-PGA production. Subsequently, C. glutamicum F343 with a strong L-glutamic acid production capability was tested. C. glutamicum F343 carrying capBCA produced γ-PGA up to 11.4 g/L, showing a higher titer compared with C. glutamicum F343 expressing pgsBCA. By introducing B. subtilis glutamate racemase gene racE under Ptac promoter mutants with different expression strength, the percentage of L-glutamic acid units in γ-PGA could be adjusted from 97.1% to 36.9%, and stayed constant during the fermentation process, while the γ-PGA titer reached 21.3 g/L under optimal initial glucose concentrations. The molecular weight (Mw) of γ-PGA in the engineered strains ranged from 2000 to 4000 kDa. This work provides a foundation for the development of sustainable and cost-effective de novo production of γ-PGA from glucose with customized ratios of L-glutamic acid in C. glutamicum.
Collapse
|
27
|
Ziemba AM, Lane KP, Balouch B, D'Amato AR, Totsingan F, Gross RA, Gilbert RJ. Lactonic Sophorolipid Increases Surface Wettability of Poly-l-lactic Acid Electrospun Fibers. ACS APPLIED BIO MATERIALS 2019; 2:3153-3158. [PMID: 35030759 DOI: 10.1021/acsabm.9b00268] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The hydrophobicity of electrospun poly-l-lactic acid (PLLA) fibers hinders their integration with surrounding tissue for a variety of applications. In this study, we increased PLLA fiber hydrophilicity by incorporating the natural surfactant, lactonic sophorolipid (LSL). PLLA+LSL fibers had similar fiber morphology but significantly greater surface wettability, which suggested LSL accumulation on the fiber surface. Differential scanning calorimetry results also suggested that LSL was phase separated from PLLA. Despite the altered surface wettability of these fibers, there was no change in fibroblast adhesion. Future studies may explore the use of this natural surfactant to deliver bioactive factors to enhance fibroblast adhesion.
Collapse
|
28
|
Hollande L, Do Marcolino I, Balaguer P, Domenek S, Gross RA, Allais F. Preparation of Renewable Epoxy-Amine Resins With Tunable Thermo-Mechanical Properties, Wettability and Degradation Abilities From Lignocellulose- and Plant Oils-Derived Components. Front Chem 2019; 7:159. [PMID: 30972325 PMCID: PMC6445855 DOI: 10.3389/fchem.2019.00159] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2018] [Accepted: 03/04/2019] [Indexed: 11/30/2022] Open
Abstract
One-hundred percent renewable triphenol—GTF—(glycerol trihydroferulate) and novel bisphenols—GDFx–(glycerol dihydroferulate) were prepared from lignocellulose-derived ferulic acid and vegetal oil components (fatty acids and glycerol) using highly selective lipase-catalyzed transesterifications. Estrogenic activity tests revealed no endocrine disruption for GDFx bisphenols. Triethyl-benzyl-ammonium chloride (TEBAC) mediated glycidylation of all bis/triphenols, afforded innocuous bio-based epoxy precursors GDFxEPO and GTF-EPO. GDFxEPO were then cured with conventional and renewable diamines, and some of them in presence of GTF-EPO. Thermo-mechanical analyses (TGA, DSC, and DMA) and degradation studies in acidic aqueous solutions of the resulting epoxy-amine resins showed excellent thermal stabilities (Td5% = 282–310°C), glass transition temperatures (Tg) ranging from 3 to 62°C, tunable tan α, and tunable degradability, respectively. It has been shown that the thermo-mechanical properties, wettability, and degradability of these epoxy-amine resins, can be finely tailored by judiciously selecting the diamine nature, the GTF-EPO content, and the fatty acid chain length.
Collapse
|
29
|
Peters KC, Mekala S, Gross RA, Singer KD. Cooperative Self-Assembly of Helical Exciton-Coupled Biosurfactant-Functionalized Porphyrin Chromophores. ACS APPLIED BIO MATERIALS 2019; 2:1703-1713. [DOI: 10.1021/acsabm.9b00086] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
30
|
Hu J, Sanders C, Mekala S, Chen TY, Cunningham MF, Gross RA. A Zwitterionic Polymerizable Surfactant from ω-Hydroxyltetradecanoic Acid Provides Stimuli-Responsive Behavior. Macromolecules 2019. [DOI: 10.1021/acs.macromol.8b02541] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
31
|
Diaz-Rodriguez P, Chen H, Erndt-Marino JD, Liu F, Totsingan F, Gross RA, Hahn MS. Impact of Select Sophorolipid Derivatives on Macrophage Polarization and Viability. ACS APPLIED BIO MATERIALS 2018; 2:601-612. [DOI: 10.1021/acsabm.8b00799] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
32
|
Arabiyat AS, Diaz-Rodriguez P, Erndt-Marino JD, Totsingan F, Mekala S, Gross RA, Hahn MS. Effect of Poly(sophorolipid) Functionalization on Human Mesenchymal Stem Cell Osteogenesis and Immunomodulation. ACS APPLIED BIO MATERIALS 2018; 2:118-126. [DOI: 10.1021/acsabm.8b00434] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
33
|
Liu F, McMaster M, Mekala S, Singer K, Gross RA. Grown Ultrathin Bacterial Cellulose Mats for Optical Applications. Biomacromolecules 2018; 19:4576-4584. [DOI: 10.1021/acs.biomac.8b01269] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
|
34
|
Su A, Tyrikos-Ergas T, Shirke AN, Zou Y, Dooley AL, Pavlidis IV, Gross RA. Revealing Cutinases’ Capabilities as Enantioselective Catalysts. ACS Catal 2018. [DOI: 10.1021/acscatal.8b02099] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
|
35
|
Ziemba AM, Lane KP, San Segundo IM, D'Amato AR, Mason AK, Sexton RJ, Casajus H, Gross RA, Corr DT, Gilbert RJ. Poly-l-lactic acid- co-poly(pentadecalactone) Electrospun Fibers Result in Greater Neurite Outgrowth of Chick Dorsal Root Ganglia in Vitro Compared to Poly-l-lactic Acid Fibers. ACS Biomater Sci Eng 2018; 4:1491-1497. [PMID: 33445306 DOI: 10.1021/acsbiomaterials.8b00013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electrospun poly-l-lactic acid (PLLA) fiber scaffolds are used to direct axonal extension in neural engineering models. We aimed to improve the efficacy of these fibers in promoting neurite outgrowth by altering surface topography and reducing fiber elastic modulus through the incorporation of a compatibilized blend, poly-l-lactic acid-poly(pentadecalactone) (PLLA-PPDL) into the solution prior to electrospinning. PLLA+PLLA-PPDL fibers had a larger diameter, increased surface nanotopography, and lower glass transition temperature than PLLA fibers but had similar mechanical properties. Increases in neurite outgrowth on PLLA+PLLA-PPDL fibers were observed, potentially due to the significantly increased diameter and surface coverage with nanotopography. Ultimately, these results suggest that greater electrospun fiber diameter and surface topography may contribute to increases in neurite outgrowth.
Collapse
|
36
|
Totsingan F, Centore R, Gross RA. CAL-B catalyzed regioselective bulk polymerization of l-aspartic acid diethyl ester to α-linked polypeptides. Chem Commun (Camb) 2018; 53:4030-4033. [PMID: 28345083 DOI: 10.1039/c7cc01300k] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
This paper reports that the bulk polymerization of l-aspartic acid diethyl ester catalyzed by immobilized CAL-B at 80 °C for 24 h gives primarily (∼95%) α-linked poly(l-aspartate) in 70% yield with DPavg = 50 and regioselectivity (α/β) = 94 : 6. Plots of log{[M]0/[M]t} vs. time and DPavgvs. conversion indicate that this polymerization proceeds in a controlled manner by a chain-growth mechanism up to 90% conversion. Thereafter, competition occurs between chain growth and step mechanisms.
Collapse
|
37
|
Shirke AN, White C, Englaender JA, Zwarycz A, Butterfoss GL, Linhardt RJ, Gross RA. Stabilizing Leaf and Branch Compost Cutinase (LCC) with Glycosylation: Mechanism and Effect on PET Hydrolysis. Biochemistry 2018; 57:1190-1200. [PMID: 29328676 DOI: 10.1021/acs.biochem.7b01189] [Citation(s) in RCA: 89] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cutinases are polyester hydrolases that show a remarkable capability to hydrolyze polyethylene terephthalate (PET) to its monomeric units. This revelation has stimulated research aimed at developing sustainable and green cutinase-catalyzed PET recycling methods. Leaf and branch compost cutinase (LCC) is particularly suited toward these ends given its relatively high PET hydrolysis activity and thermostability. Any practical enzymatic PET recycling application will require that the protein have kinetic stability at or above the PET glass transition temperature (Tg, i.e., 70 °C). This paper elucidates the thermodynamics and kinetics of LCC conformational and colloidal stability. Aggregation emerged as a major contributor that reduces LCC kinetic stability. In its native state, LCC is prone to aggregation owing to electrostatic interactions. Further, with increasing temperature, perturbation of LCC's tertiary structure and corresponding exposure of hydrophobic domains leads to rapid aggregation. Glycosylation was employed in an attempt to impede LCC aggregation. Owing to the presence of three putative N-glycosylation sites, expression of native LCC in Pichia pastoris resulted in the production of glycosylated LCC (LCC-G). LCC-G showed improved stability to native state aggregation while increasing the temperature for thermal induced aggregation by 10 °C. Furthermore, stabilization against thermal aggregation resulted in improved catalytic PET hydrolysis both at its optimum temperature and concentration.
Collapse
|
38
|
Mekala S, Peters KC, Singer KD, Gross RA. Biosurfactant-functionalized porphyrin chromophore that forms J-aggregates. Org Biomol Chem 2018; 16:7178-7190. [DOI: 10.1039/c8ob01655k] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Synthesis of sophorolipid-porphyrin conjugates with built-in variations in non-covalent interactions, H–bonding, π–π stacking, and hydrophobic interactions for supramolecular self-assembly.
Collapse
|
39
|
He W, Zhu Y, Shirke A, Sun X, Liu J, Gross RA, Koffas MAG, Linhardt RJ, Li M. Expression of chondroitin-4-O-sulfotransferase in Escherichia coli and Pichia pastoris. Appl Microbiol Biotechnol 2017; 101:6919-6928. [DOI: 10.1007/s00253-017-8411-5] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2017] [Revised: 06/23/2017] [Accepted: 06/26/2017] [Indexed: 10/19/2022]
|
40
|
Koh A, Todd K, Sherbourne E, Gross RA. Fundamental Characterization of the Micellar Self-Assembly of Sophorolipid Esters. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:5760-5768. [PMID: 28510440 DOI: 10.1021/acs.langmuir.7b00480] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Surfactants are ubiquitous constituents of commercial and biological systems that function based on complex structure-dependent interactions. Sophorolipid (SL) n-alkyl esters (SL-esters) comprise a group of modified naturally derived glycolipids from Candida bombicola. Herein, micellar self-assembly behavior as a function of SL-ester chain length was studied. Surface tensions as low as 31.2 mN/m and critical micelle concentrations (CMCs) as low as 1.1 μM were attained for diacetylated SL-decyl ester (dASL-DE) and SL-octyl ester, respectively. For deacetylated SL-esters, CMC values reach a lower limit at SL-ester chains above n-butyl (SL-BE, 1-3 μM). This behavior of SL-esters with increasing hydrophobic tail length is unlike other known surfactants. Diffusion-ordered spectroscopy (DOSY) and T1 relaxation NMR experiments indicate this behavior is due to a change in intramolecular interactions, which impedes the self-assembly of SL-esters with chain lengths above SL-BE. This hypothesis is supported by micellar thermodynamics where a disruption in trends occurs at n-alkyl ester chain lengths above those of SL-BE and SL-hexyl ester (SL-HE). Diacetylated (dA) SL-esters exhibit an even more unusual trend in that CMC increases from 1.75 to 815 μM for SL-ester chain lengths of dASL-BE and dASL-DE, respectively. Foaming studies, performed to reveal the macroscopic implications of SL-ester micellar behavior, show that the observed instability in foams formed using SL-esters are due to coalescence, which highlights the importance of understanding intermicellar interactions. This work reveals that SL-esters are an important new family of green high-performing surfactants with unique structure-property relationships that can be tuned to optimize micellar characteristics.
Collapse
|
41
|
Shirke AN, Butterfoss GL, Saikia R, Basu A, Maria L, Svendsen A, Gross RA. Engineered
Humicola insolens
cutinase for efficient cellulose acetate deacetylation. Biotechnol J 2017; 12. [DOI: 10.1002/biot.201700188] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2017] [Revised: 05/02/2017] [Accepted: 05/09/2017] [Indexed: 12/22/2022]
|
42
|
Ziemba AM, Gottipati MK, Totsingan F, Hanes CM, Gross RA, Lennartz MR, Gilbert RJ. Sophorolipid Butyl Ester Diacetate Does Not Affect Macrophage Polarization but Enhances Astrocytic Glial Fibrillary Acidic Protein Expression at Micromolar Concentrations in Vitro. ACS Chem Neurosci 2017; 8:752-758. [PMID: 28140557 DOI: 10.1021/acschemneuro.6b00451] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Peritoneal macrophages (PMACs) and spinal cord astrocytes were exposed to varying concentrations of soluble sophorolipid butyl ester diacetate (SLBEDA) in vitro. Macrophages and astrocytes demonstrated no decrease in viability in response to SLBEDA. Studying pro- and anti-inflammatory genes, PMACs did not show a shift toward a pro-inflammatory phenotype. However, at higher concentrations (3 and 30 μM), astrocytes showed an increase in their expression of glial acidic fibrillary protein. This novel category of compounds poses low risk to PMAC and astrocyte viability; however, the effect on PMAC polarization and astrocyte reactivity requires more elucidation.
Collapse
|
43
|
Englaender JA, Zhu Y, Shirke AN, Lin L, Liu X, Zhang F, Gross RA, Koffas MAG, Linhardt RJ. Expression and secretion of glycosylated heparin biosynthetic enzymes using Komagataella pastoris. Appl Microbiol Biotechnol 2016; 101:2843-2851. [PMID: 27975137 DOI: 10.1007/s00253-016-8047-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2016] [Revised: 11/28/2016] [Accepted: 12/01/2016] [Indexed: 02/08/2023]
Abstract
Heparin, an anticoagulant drug, is biosynthesized in selected animal cells. The heparin biosynthetic enzymes mainly consist of sulfotransferases and all are integral transmembrane glycoproteins. These enzymes are generally produced in engineered Escherichia coli as without their transmembrane domains as non-glycosylated fusion proteins. In this study, we used the yeast, Komagataella pastoris, to prepare four sulfotransferases involved in heparin biosynthesis as glycoproteins. While the yields of these yeast-expressed enzymes were considerably lower than E. coli-expressed enzymes, these enzymes were secreted into the fermentation media simplifying their purification and were endotoxin free. The activities of these sulfotransferases, expressed as glycoproteins in yeast, were compared to the bacterially expressed proteins. The yeast-expressed sulfotransferase glycoproteins showed improved kinetic properties than the bacterially expressed proteins.
Collapse
|
44
|
Varghai D, Maiorana A, Meng Q, Gross RA, Manas-Zloczower I. Sustainable, electrically-conductive bioepoxy nanocomposites. POLYMER 2016. [DOI: 10.1016/j.polymer.2016.11.028] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
|
45
|
Fiorani A, Totsingan F, Pollicino A, Peng Y, Focarete ML, Gross RA, Scandola M. Peptide Modified Electrospun Glycopolymer Fibers. Macromol Biosci 2016; 17. [DOI: 10.1002/mabi.201600327] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2016] [Revised: 09/14/2016] [Indexed: 11/11/2022]
|
46
|
Shirke AN, Su A, Jones JA, Butterfoss GL, Koffas MA, Kim JR, Gross RA. Comparative thermal inactivation analysis ofAspergillus oryzaeandThiellavia terrestriscutinase: Role of glycosylation. Biotechnol Bioeng 2016; 114:63-73. [DOI: 10.1002/bit.26052] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2016] [Revised: 07/01/2016] [Accepted: 07/11/2016] [Indexed: 12/11/2022]
|
47
|
Patel A, Maiorana A, Yue L, Gross RA, Manas-Zloczower I. Curing Kinetics of Biobased Epoxies for Tailored Applications. Macromolecules 2016. [DOI: 10.1021/acs.macromol.6b01261] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
|
48
|
Zhang X, Khalidi O, Kim SY, Wang R, Schultz V, Cress BF, Gross RA, Koffas MAG, Linhardt RJ. Synthesis and biological evaluation of 5,7-dihydroxyflavanone derivatives as antimicrobial agents. Bioorg Med Chem Lett 2016; 26:3089-3092. [PMID: 27210435 PMCID: PMC7927313 DOI: 10.1016/j.bmcl.2016.05.003] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Revised: 05/02/2016] [Accepted: 05/03/2016] [Indexed: 12/25/2022]
Abstract
A series of 5,7-dihydroxyflavanone derivatives were efficiently synthesized. Their antimicrobial efficacy on Gram-negative, Gram-positive bacteria and yeast were evaluated. Among these compounds, most of the halogenated derivatives exhibited the best antimicrobial activity against Gram-positive bacteria, the yeast Saccharomyces cerevisiae, and the Gram-negative bacterium Vibrio cholerae. The cytotoxicities of these compounds were low as evaluated on HepG2 cells using a cell viability assay. This study suggests that halogenated flavanones might represent promising pharmacological candidates for further drug development.
Collapse
|
49
|
Maiorana A, Subramaniam B, Centore R, Han X, Linhardt RJ, Gross RA. Synthesis and characterization of an adipic acid-derived epoxy resin. ACTA ACUST UNITED AC 2016. [DOI: 10.1002/pola.28142] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
50
|
Shirke AN, Basore D, Butterfoss GL, Bonneau R, Bystroff C, Gross RA. Toward rational thermostabilization of Aspergillus oryzae cutinase: Insights into catalytic and structural stability. Proteins 2015; 84:60-72. [PMID: 26522152 DOI: 10.1002/prot.24955] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2015] [Revised: 10/11/2015] [Accepted: 10/12/2015] [Indexed: 11/10/2022]
Abstract
Cutinases are powerful hydrolases that can cleave ester bonds of polyesters such as poly(ethylene terephthalate) (PET), opening up new options for enzymatic routes for polymer recycling and surface modification reactions. Cutinase from Aspergillus oryzae (AoC) is promising owing to the presence of an extended groove near the catalytic triad which is important for the orientation of polymeric chains. However, the catalytic efficiency of AoC on rigid polymers like PET is limited by its low thermostability; as it is essential to work at or over the glass transition temperature (Tg) of PET, that is, 70 °C. Consequently, in this study we worked toward the thermostabilization of AoC. Use of Rosetta computational protein design software in conjunction with rational design led to a 6 °C improvement in the thermal unfolding temperature (Tm) and a 10-fold increase in the half-life of the enzyme activity at 60 °C. Surprisingly, thermostabilization did not improve the rate or temperature optimum of enzyme activity. Three notable findings are presented as steps toward designing more thermophilic cutinase: (a) surface salt bridge optimization produced enthalpic stabilization, (b) mutations to proline reduced the entropy loss upon folding, and (c) the lack of a correlative increase in the temperature optimum of catalytic activity with thermodynamic stability suggests that the active site is locally denatured at a temperature below the Tm of the global structure.
Collapse
|