Breeding Of Acid-tolerant Mutants Of Clostridium Propionicum And The Potentials For Acrylate Production

Acrylic acid is an important chemical raw material with widely applications in coatings, textiles, adhesives, paper, polishing agent, leather, chemical fiber, high-absorbent resin and other industries.In the present study, we found the Lineweaver-Burk equation of propionate oxidation to acrylate is: y = 6231.3x + 79.606, and the Km and Vmax were 78.277 mmol/L and 0.7536 mmol/L-min respectively when using resting cells of Clostridium propionicum. We aslo studied the primary optimization of single factors of this reaction.Different concentrations of acrylic acid were added into the medium at different pH conditions, and the optimal pH for cell growth was found to be 7.0, the final concentration of acetic and propionic acid reached 1.32 g/L and 3.21 g/L respectively, and the A/P ratio is also the minimum (about 0.5). The results also showed that acrylic acid slowed the growth rate significantly, which made Clostridium propioncum take relatively long lag duration, a decreased OD value of delayed stationary phase and an increased amount of the acid with decreased A/P ratio.Through the domestication of Clostridium propioncum with the medium pH 7.0, the resistantance to acrylic acid increased from 1.5 g/L to 2.5 g/L.Repeated experiments of ultraviolet and DES mutation showed that the DES mutation made better effection than UV mutation. After UV mutation, the acrylic tolerance doubled, which was 3 g/L; while the DES mutation strain could tolerate 9 g/L acrylic acid which was six times before mutation.This paper also studied the effects of acrylic acid and pH on two DES mutants which can tolerate 5 g/L and 9 g/L acrylic acid respectively. The results showed that the pH scope of both mutants broadened, yet the growth and acid production were poorer than the original strains. After the mutation, the A/P ratio became higher. Acrylic acid had the similar effect on both mutants and original strains.