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Fractionation and characterization of poly(β-L-malic acid) produced by Aureobasidium melanogenum ipe-1

Changsheng Qiao1, Guohang Sun2, Hongbao Li3

  • 1College of Biotechnology, Tianjin University of Science and Technology, Tianjin 300457, PR China.

International Journal of Biological Macromolecules
|May 14, 2023
PubMed

Insights

Poly (β-L-malic acid) (PMLA) was fractionated using membranes, revealing distinct molecular sizes and a glucose-terminated structure. This characterization aids industrial applications of PMLA from Aureobasidium melanogenum.

Area of Science:

  • Biotechnology and Biomaterials Science
  • Polymer Chemistry
  • Industrial Microbiology

Background:

  • Poly (β-L-malic acid) (PMLA) shows industrial promise, particularly in medicine, but its molecular characteristics and fractionation methods are not well understood.
  • Aureobasidium spp. are known producers of PMLA, yet detailed fractionation and characterization of their PMLA products remain unclear.

Purpose of the Study:

  • To effectively fractionate and characterize Poly (β-L-malic acid) (PMLA) produced by Aureobasidium melanogenum ipe-1.
  • To elucidate the molecular size distribution, polydispersity, and structural features of fractionated PMLA.
  • To provide insights into membrane fouling mechanisms during PMLA fractionation.

Main Methods:

  • Fractionation of PMLA using 300 kDa and 50 kDa membranes.
  • Analysis of membrane fouling mechanisms during filtration and diafiltration.
  • Determination of molecular weight (Mw), number-average molecular weight (Mn), and polydispersity index (Mw/Mn) of PMLA fractions.
  • Structural characterization using Nuclear Magnetic Resonance (NMR), High-Performance Liquid Chromatography (HPLC), and Fourier-Transform Infrared Spectroscopy (FTIR).

Main Results:

  • Effective fractionation of PMLA was achieved using 300 kDa and 50 kDa membranes, yielding fractions with distinct molecular weights (75,134 Da, 21,344 Da, and 10,056 Da).
  • The polydispersity indices (Mw/Mn) of the PMLA fractions were 4.12, 1.92, and 1.12, indicating varying degrees of molecular homogeneity.
  • Spectroscopic analysis (NMR, HPLC, FTIR) confirmed the product as glucose-terminated PMLA, with glucose attached to the terminal hydroxyl group, not simple L-malic acid monomers.
  • Membrane fouling mechanisms were complex, varying between standard and complete blocking during diafiltration due to PMLA's ability to both permeate and reject membranes.

Conclusions:

  • The study successfully fractionated PMLA from Aureobasidium melanogenum ipe-1, providing valuable data on molecular size distribution and polydispersity.
  • The identification of glucose-terminated PMLA provides crucial structural information for understanding its properties and functions.
  • These findings offer a significant guide for optimizing process design and operational strategies in the industrial application of PMLA.
Keywords:
Acidic polysaccharideAureobasidium pullulansMolecular weightPoly(β-L-malic acid)

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