Rapid expansion of global market of lactic acid (LA) has prompted research towards cheaper and more eco-friendly strategies for its production. Nowadays, LA is produced mainly through fermentation of simple sugars or starchy biomass (e.g. corn) and its price is relatively high. Lignocellulose could be an advantageous alternative feedstock for LA production owing to its high abundance and low cost. However, the most effective natural producers of LA cannot directly ferment lignocellulose. So far, metabolic engineering aimed at developing microorganisms combining efficient LA production and cellulose hydrolysis has been generally based on introducing designer cellulase systems in natural LA producers. In the present study, the approach consisted in improving LA production in the natural cellulolytic bacterium Clostridium thermocellum DSM1313. The expression of the native lactate dehydrogenase was enhanced by functional replacement of its original promoter with stronger ones resulting in a 10-fold increase in specific activity, which resulted in a 2-fold increase of LA yield. It is known that eliminating allosteric regulation can also increase lactic acid production in C. thermocellum, however we were unable to insert strong promoters upstream of the de-regulated ldh gene. A strategy combining these regulations and inactivation of parasitic pathways appears essential for developing a homolactic C. thermocellum.

Construction of lactic acid overproducing Clostridium thermocellum through enhancement of lactate dehydrogenase expression

Mazzoli R.
First
;
2020

Abstract

Rapid expansion of global market of lactic acid (LA) has prompted research towards cheaper and more eco-friendly strategies for its production. Nowadays, LA is produced mainly through fermentation of simple sugars or starchy biomass (e.g. corn) and its price is relatively high. Lignocellulose could be an advantageous alternative feedstock for LA production owing to its high abundance and low cost. However, the most effective natural producers of LA cannot directly ferment lignocellulose. So far, metabolic engineering aimed at developing microorganisms combining efficient LA production and cellulose hydrolysis has been generally based on introducing designer cellulase systems in natural LA producers. In the present study, the approach consisted in improving LA production in the natural cellulolytic bacterium Clostridium thermocellum DSM1313. The expression of the native lactate dehydrogenase was enhanced by functional replacement of its original promoter with stronger ones resulting in a 10-fold increase in specific activity, which resulted in a 2-fold increase of LA yield. It is known that eliminating allosteric regulation can also increase lactic acid production in C. thermocellum, however we were unable to insert strong promoters upstream of the de-regulated ldh gene. A strategy combining these regulations and inactivation of parasitic pathways appears essential for developing a homolactic C. thermocellum.
141
109645
-
Anaerobic bacteria; Ethanol; Lignocellulose; Metabolic engineering; Transcriptional promoter
Mazzoli R.; Olson D.G.; Lynd L.R.
File in questo prodotto:
File Dimensione Formato  
ENZMICTEC-S-20-00426.pdf

Accesso aperto

Descrizione: Articolo completo
Tipo di file: PREPRINT (PRIMA BOZZA)
Dimensione 1.66 MB
Formato Adobe PDF
1.66 MB Adobe PDF Visualizza/Apri

I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.

Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/2318/1758022
Citazioni
  • ???jsp.display-item.citation.pmc??? ND
  • Scopus 6
  • ???jsp.display-item.citation.isi??? 6
social impact