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Inducible Operons: lac Operon

Inducible Operons: lac Operon

The lac operon in Escherichia coli is a model for understanding inducible gene regulation and metabolic flexibility. It integrates local control by lactose and global regulation through catabolite repression, enabling E. coli to preferentially metabolize glucose when available and switch to lactose utilization when glucose is scarce.Structure and Function of the lac OperonThe lac operon contains three structural genes: lacZ (β-galactosidase), lacY (lactose permease), and lacA...

Operons

Operons

Prokaryotes can control gene expression through operons—DNA sequences consisting of regulatory elements and clustered, functionally related protein-coding genes. Operons use a single promoter sequence to initiate transcription of a gene cluster (i.e., a group of structural genes) into a single mRNA molecule. The terminator sequence ends transcription. An operator sequence, located between the promoter and structural genes, prohibits the operon’s transcriptional activity if bound by...

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Related Experiment Video

Updated: Feb 24, 2026

Author Spotlight: Methods for Electroporation and Transformation Confirmation in Limosilactobacillus reuteri DSM20016

Author Spotlight: Methods for Electroporation and Transformation Confirmation in Limosilactobacillus reuteri DSM20016

Published on: June 23, 2023

Recombinant Lactococcus lactis for efficient conversion of cellodextrins into L-lactic acid.

Chiara Gandini¹, Loredana Tarraran¹, Denis Kalemasi¹

¹Department of Life Sciences and Systems Biology, Structural and Functional Biochemistry, Laboratory of Proteomics and Metabolic Engineering of Prokaryotes, University of Turin, Torino, Italy.

Biotechnology and Bioengineering

|August 13, 2017

Summary

Engineered lactic acid bacteria (LAB) can now ferment cellooligosaccharides into lactic acid (LA). This breakthrough advances cost-effective bioprocessing for biodegradable plastics.

Keywords:

beta-glycosidase cellulase metabolic engineering polylactide recombinant cellulolytic strategy

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Light-Controlled Fermentations for Microbial Chemical and Protein Production

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Last Updated: Feb 24, 2026

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Light-Controlled Fermentations for Microbial Chemical and Protein Production

Light-Controlled Fermentations for Microbial Chemical and Protein Production

Published on: March 22, 2022

Area of Science:

Biotechnology
Microbial Engineering
Industrial Microbiology

Background:

Lactic acid bacteria (LAB) are crucial for industrial applications, including food production and biorefineries.
Lactic acid (LA) is a valuable chemical, with its polymers (polylactides) offering biodegradable alternatives to plastics.
Current LA production via LAB fermentation is expensive, hindering polylactide competitiveness due to LAB's complex nutritional needs and inability to ferment inexpensive substrates like cellulose.

Purpose of the Study:

To metabolically engineer a Lactococcus lactis strain for direct fermentation of cellulose-derived oligosaccharides.
To reduce nutritional requirements of LAB and enable direct utilization of low-cost polysaccharides.
To develop a cost-effective method for producing optically pure lactic acid from biomass.

Main Methods:

Genetic engineering of Lactococcus lactis to constitutively secrete β-glucosidase and endoglucanase enzymes.
Fermentation trials using engineered LAB strains on cellooligosaccharides.
Analysis of growth and lactic acid production from cellooligosaccharide substrates.

Main Results:

The engineered Lactococcus lactis strain successfully grew on cellooligosaccharides up to cellooctaose.
The recombinant strain efficiently converted cellooligosaccharides into L-lactic acid in a single fermentation step.
This marks the first instance of LAB directly metabolizing cellooligosaccharides longer than cellohexaose.

Conclusions:

Metabolic engineering has enabled LAB to directly utilize longer-chain cellooligosaccharides.
This advancement is a significant step towards cost-sustainable consolidated bioprocessing of cellulose into optically pure lactic acid.
The engineered strain holds potential for reducing the cost of producing polylactides from biomass.