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Substrate Optimization for PHB Production from Ricotta Cheese Exhausted Whey Using Azohydromonas lata DSM 1123
Angela Longo1, Luca Sconosciuto2, Michela Verni1
1Department of Environmental Biology, Sapienza University of Rome, 00185 Rome, Italy.
Microorganisms
|August 28, 2025
Summary
Ricotta cheese whey valorization using *Azohydromonas lata* efficiently produces polyhydroxyalkanoates (PHAs). Optimized substrate and bioreactor conditions significantly boost microbial biomass and PHA yields, demonstrating a sustainable bioplastic production method.
Area of Science:
- Biotechnology and Industrial Microbiology
- Polymer Science
- Dairy By-product Valorization
Background:
- Ricotta cheese exhausted whey (RCEW) is a globally abundant dairy by-product with significant environmental implications.
- Valorizing RCEW is crucial for sustainability and economic benefit, offering a potential carbon source for microbial products.
- Polyhydroxyalkanoates (PHAs) are biodegradable polyesters with diverse applications, but cost-effective production remains a challenge.
Purpose of the Study:
- To investigate the feasibility of using RCEW as a substrate for polyhydroxyalkanoate (PHA) production by *Azohydromonas lata* DSM 1123.
- To optimize RCEW pre-treatment and fermentation conditions to maximize microbial biomass and PHA yield.
- To characterize the produced PHA polymer.
Main Methods:
- Characterization of RCEW composition, including lactose, protein, and fat content.
- Optimization of RCEW pre-treatment involving pasteurization, sterilization, and mineral/enzyme supplementation (β-galactosidase).
- Fermentation trials using *A. lata* under varying conditions (nitrogen limitation, C/N ratio, fed-batch) in bioreactors.
- Analysis of microbial biomass, intracellular PHA content, and PHA yield.
- Characterization of the extracted polymer (polyhydroxybutyrate, PHB) for thermal stability and molecular weight.
Main Results:
- RCEW contains significant lactose (3.81%) but requires β-galactosidase for *A. lata* metabolism.
- Optimized RCEW pre-treatment (pasteurized-sterilized mixture, mineral supplementation) enhanced biomass and PHA content to 25.94%.
- Moderate nitrogen limitation (C/N 44) and fed-batch fermentation in bioreactors further increased PHA production to 0.88 g/L (32.74% intracellular accumulation).
- The produced polymer was identified as polyhydroxybutyrate (PHB) with high thermal stability and a molecular weight of 5.9 KDa.
Conclusions:
- Ricotta cheese exhausted whey is a viable and cost-effective substrate for polyhydroxyalkanoate (PHA) production using *Azohydromonas lata*.
- Optimized substrate pre-treatment and fermentation strategies, including fed-batch operation, are key to maximizing PHA yield.
- This study demonstrates a sustainable approach for dairy waste valorization and the production of biodegradable polymers.
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