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Purification and polymerisation of microbial d-lactic acid from DDGS hydrolysates fermentation
- Zaini, Nurul Aqilah Mohd, Chatzifragkou, Afroditi, Tverezovskiy, Viacheslav, Charalampopoulos, Dimitris
- Biochemical engineering journal 2019 v.150 pp. 107265
- acidification, activated carbon, adsorption, anion exchange, anion exchange resins, binding capacity, condensation reactions, culture media, fermentation, hydrolysates, lactic acid, models, molecular weight, polymerization, polymers, purification methods
- A multi-step process was developed for microbial d-lactic acid purification, followed by poly-d-lactic acid (PDLA) synthesis via azeotropic polycondensation process. Several anion exchange resins were screened for their binding capacity using model lactic acid solutions. Amberlite® IRA67 (weak base anion exchange resin) showed the highest lactic acid adsorption, with maximum adsorption capacity, qmax, of 136.11 mg lactic acid / g of resin, and was further selected to purify D-lactic acid from DDGS hydrolysates through a three-step process; (1) treatment with 7% w/v activated carbon, (2) acidification of fermentation broth (Amberlite® IRA120) and (3) adsorption of lactic acid by anion exchange (Amberlite® IRA67). At the end of the purification process, 80.4% (w/w) D-lactic acid was recovered with 91.8% (w/w) purity, indicating the effectiveness of the developed downstream process. Furthermore, a clear yellowish solid polymer with a molecular weight of 3010 Da was obtained, suitable for applications in biomedical and agricultural sectors.