Dong Wang

Jiangnan University, Wu-hsi, Jiangsu Sheng, China

Are you Dong Wang?

Claim your profile

Publications (8)20 Total impact

  • Qun Wu, Yamin Zhao, Dong Wang, Yan Xu
    [Show abstract] [Hide abstract]
    ABSTRACT: Rhodotorula mucilaginosa, producing the ethyl carbamate (EC)-degrading enzyme, urethanase, was newly isolated from the Chinese rice wine making process. It removed 80 % of EC when it was incubated with 5.0 g/L EC. It grew and stably produced urethanase, with pH ranging from 7.0 to 3.0. In addition, urethanase production by R. mucilaginosa was systematically optimized. Glucose, yeast extract, peptone, and inoculum size were selected with the Plackett-Burman design. They were further optimized via uniform design and determined to be 24.6 g/L, 2.5 g/L, 23.1 g/L, and 65.8 mL/500 mL, respectively. Urethanase activity reached 4,340.0 U/L in the optimal fermentation condition. Furthermore, cell immobilization of R. mucilaginosa in calcium alginate/chitosan was applied to improve cell resistance to environmental stresses. The immobilized cells removed 51.6 % of EC in commercial rice wine, which was 10 times more than that of the free cells. It indicated that the immobilized R. mucilaginosa was effective for degrading EC.
    Applied biochemistry and biotechnology 09/2013; · 1.94 Impact Factor
  • ChemInform 12/2012; 43(50).
  • [Show abstract] [Hide abstract]
    ABSTRACT: The earliest industrial biotechnology originated in ancient China and developed into a vibrant industry in traditional Chinese liquor, rice wine, soy sauce, and vinegar. It is now a significant component of the Chinese economy valued annually at about 150 billion RMB. Although the production methods had existed and remained basically unchanged for centuries, modern developments in biotechnology and related fields in the last decades have greatly impacted on these industries and led to numerous technological innovations. In this chapter, the main biochemical processes and related technological innovations in traditional Chinese biotechnology are illustrated with recent advances in functional microbiology, microbial ecology, solid-state fermentation, enzymology, chemistry of impact flavor compounds, and improvements made to relevant traditional industrial facilities. Recent biotechnological advances in making Chinese liquor, rice wine, soy sauce, and vinegar are reviewed.
    Advances in biochemical engineering/biotechnology 11/2009; 122:189-233. · 1.64 Impact Factor
  • Shu Yang Sun, Yan Xu, Dong Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: To identify which solid-state typical environmental factors are involved in the induction of a solid-state special lipase (Lip1), western blot and Elisa based on Lip1 antibody were used. A low water activity played a significant role in the induction of Lip1, as evidenced by the increased expression level (20-46 microg/g dry cell) along with the decrease of water activity (0.927-0.969). Physical barrier against hyphal extension was found to be another required factor, since the expression of Lip1 was significantly enhanced by 3-fold using a membrane with smaller pore size (0.45 and 0.22 microm) covered on top of surface culture.
    Bioresource Technology 07/2009; 100(12):3152-6. · 4.75 Impact Factor
  • Shu Yang Sun, Yan Xu, Dong Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: Rhizopus chinensis produces two lipases that catalyze ester synthesis when cultured under solid-state fermentation. The Lip2 was purified to homogeneity by ammonium sulphate precipitation, hydrophobic interaction chromatography and gel filtration chromatography. It has an apparent molecular weight of 33 kDa estimated from SDS-PAGE and 32 kDa calculated from analytical gel permeation, with synthetic activity and purification fold of 96.8 U/mg and 138.3, respectively. Maximum hydrolytic activity was obtained at pH 8.0-8.5 and 40 degrees C using pNPP as substrate. Slight activation of the enzyme was observed when Mn(2+) is present. The enzyme was most active on p-nitrophenyl laurate (C12). The purified lipase exhibited maximum synthetic activity at pH memory of 6.0 and 30 degrees C. Most of ethyl esters synthesized by lyophilized enzyme achieved good yields (>90%), and caprylic acid served as the best acyl donor. The enzyme presented a particular affinity for ethanol, n-propanol and n-hexanol, with conversion of 92%, 93% and 92%, respectively, after 20 h incubation.
    Bioresource Technology 01/2009; 100(9):2607-12. · 4.75 Impact Factor
  • Shu Yang Sun, Yan Xu, Dong Wang
    [Show abstract] [Hide abstract]
    ABSTRACT: BACKGROUND: Purification and characterization of an intracellular lipase produced by Rhizopus chinenesis cultured in solid-state fermentation was investigated. The potential application in concentrating eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) from fish oil by the pure enzyme was also studied.RESULTS: Through four successive purification steps, the enzyme was purified to homogeneity with an apparent molecular mass of 36 kDa. The lipase was active for pH between 7.0 and 9.0 and temperatures 20–45 °C. Lipase activity was slightly increased in the presence of Ca2+ and Mg2+, but strongly inhibited by Hg2+ and SDS. The pure enzyme was most active on medium chain p-nitrophenol esters, with the highest activity towards pNP-caprylate (C8). The enzyme is a non-specific lipase, because it cleaved not only the 1,3-positioned ester bonds but also the 2-positioned bond in triolein. High EPA (17.6%) and DHA (32.9%) contents were achieved using the pure lipase (100 U) within 10 h.CONCLUSION: The enzymatic activity of the lipase on a wide variety of substrates and its stability in the presence of some organic solvents suggest that the lipase should be investigated for a range of commercial applications. The pure lipase was proved to possess potential ability for the production and concentration of EPA and DHA from fish oil. Copyright © 2008 Society of Chemical Industry
    Journal of Chemical Technology & Biotechnology 10/2008; 84(3):435 - 441. · 2.50 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The lipase-catalyzed esterification of sorbitan with oleic acid in a solvent-free system to form sorbitan oleate (commercial name Span80) was studied as a feasible approach aimed at meeting the demand for sugar alcohol-based surfactants. Screened results obtained from enzymatic synthesis of sorbitan oleate indicated that Novozym 435 had its highest catalytic activity in a solvent-free system. The introduction of a reduced-pressure system increased the production of sorbitan oleate to a maximum of 95% of theoretical, obtained from 0.2 mol sorbitan, 0.1 mol oleic acid, and 2.0 g lipase (6 wt% of sorbitan) in a solvent-free reaction mixture at optimal reaction conditions. Results obtained from lipase-catalyzed batch esterification reactions showed that more than 90% conversion of sorbitan oleate was maintained after 10 batches of esterification reactions, indicating excellent enzyme stability. Subsequent analysis by HPLC indicated that the product of enzyme-catalyzed esterification by the immobilized lipase contained a significantly greater amount of monoester (about 80%) compared to the composition obtained by chemical synthesis (about 50%).
    Journal of Oil & Fat Industries 06/2003; 80(7):647-651. · 1.59 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A fungal strain capable of synthesizing ethyl esters of short-chain fatty acids was isolated from leaven (mouldy grains) samples through combined screening strategy of lipolysis and with esterification ability and was identified to be Rhizopus chinesis CCTCC M201021. When compared with other 10 commercial lipases, the whole-cell lipase of R. chinesis CCTCC M201021 (RCL) showed much higher ability in the synthesis of ethyl hexanoate during the screening of suitable lipases with a maximum yield of 96.5% after 72 h conversion using 0.5 M equal molar substrate concentration. Thereafter, the effect of important reaction parameters for enhancing ester formation by whole-cell RCL was investigated in this study. Higher esterification (>90%) was observed and maintained under chain length of carboxylic acids (C2–C8). Solvents with log P (P: partition coefficient) >2.0 enhanced RCL activity to give high conversion (>88.8%). Effect of temperature on reaction showed better esterification at 30–40 °C. Increase in concentration of substrates (ethanol and acid) from 0.2 to 1.4 M led to decrease in molar conversion from 96 to 85% in the synthesis of ethyl hexanoate. Changing the molar ratio of acid/ethanol from 1:1 to 1:3 at 0.6 M acid concentration resulted in a maximal conversion of 98.5% at the ratio of 1:1.3. It was observed that better esterification could be achieved with initial water activity (aw) ranging from 0.66 to 0.97. A crucial enzyme concentration of 6 g/l was chosen for research after effect on esterification reaction was examined. The half-life period of esterification for different flavor ester production indicated that whole-cell RCL was more stable in batch esterification reaction within 840–975 h of half-life period for ethyl flavor esters.
    Journal of Molecular Catalysis B Enzymatic 01/2002; · 2.82 Impact Factor