Characterization of the starvation-induced chitinase CfcA and α-1,3-glucanase AgnB of Aspergillus niger

Jolanda M van Munster, Justyna M Dobruchowska, Ruud Veloo, Lubbert Dijkhuizen, Marc J E C van der Maarel

Research output: Contribution to journalArticle

8 Citations (Scopus)

Abstract

The common saprophyte Aspergillus niger may experience carbon starvation in nature as well as during industrial fermentations. Starvation survival strategies, such as conidiation or the formation of exploratory hyphae, require energy and building blocks, which may be supplied by autolysis. Glycoside hydrolases are key effectors of autolytic degradation of fungal cell walls, but knowledge on their identity and functionality is still limited. We recently identified agnB and cfcA as two genes encoding carbohydrate-active enzymes that had notably increased transcription during carbon starvation in A. niger. Here, we report the biochemical and functional characterization of these enzymes. AgnB is an α-1,3-glucanase that releases glucose from α-1,3-glucan substrates with a minimum degree of polymerization of 4. CfcA is a chitinase that releases dimers from the nonreducing end of chitin. These enzymes thus attack polymers that are found in the fungal cell wall and may have a role in autolytic fungal cell wall degradation in A. niger. Indeed, cell wall degradation during carbon starvation was reduced in the double deletion mutant ΔcfcA ΔagnB compared to the wild-type strain. Furthermore, the cell walls of the carbon-starved mycelium of the mutant contained a higher fraction of chitin or chitosan. The function of at least one of these enzymes, CfcA, therefore appears to be in the recycling of cell wall carbohydrates under carbon limiting conditions. CfcA thus may be a candidate effector for on demand cell lysis, which could be employed in industrial processes for recovery of intracellular products.

Original languageEnglish
Pages (from-to)2209-23
Number of pages15
JournalApplied Microbiology and Biotechnology
Volume99
Issue number5
Early online date16 Sep 2014
DOIs
Publication statusPrint publication - Mar 2015
Externally publishedYes

Keywords

  • Aspergillus niger/enzymology
  • Carbon/metabolism
  • Cell Wall/metabolism
  • Chitin/metabolism
  • Chitinases/genetics
  • Gene Deletion
  • Glucose/metabolism
  • Glycoside Hydrolases/genetics

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