Butyrate production in continuous culture of Clostridium tyrobutyricum: effect of end-product inhibition

Abstract

P r o d u c t i o n o f b u t y r a t e has b e e n studied in c o n t i n u o u s cultures o f Clostridium tyrobutyricum. Prod u c t i o n o f acids, gases a n d cell b i o m a s s were determ i n e d u n d e r c o n d i t i o n s o f glucose limitation by varying either the glucose i n p u t or the dilution rate. A d d ition of acetate or b u t y r a t e to the cultures was also b u t lower p r o d u c t c o n c e n t r a t i o n s o b t a i n e d in c o n t i n u o u s culture with respect to b a t c h or f e d -b a t c h conditions. It also e x p l a i n e d the decrease in the ratios o f b u t y r a t e to total acids a n d in cell yield observed at h i g h e r glucose i n p u t as well as the b e h a v i o u r o f the cultures u n d e r c o n d i t i o n s o f excess glucose. It could also p o s s i b l y a c c o u n t for the partial c o n v e r s i o n o f a d d e d acetate to b u t y r a t e o b s e r v e d at m o d e r a t e growth rates.

Continuous Fermentation of Clostridium tyrobutyricum with Partial Cell Recycle as a Long-Term Strategy for Butyric Acid Production

“…Higher total acid yields are attained at reduced pH, but higher butyrate selectivities and concentrations are attained at increased pH. To date, most of the research [1,[11][12][13][15][16][17][18] conducted with C. tyrobutyricum was done at relatively low pH because of recovery concerns, as solvent extraction recovers free acid only, although organic acid separation techniques such as electrodeionization [19,20] are being developed to separate organic acids at high pH. Thus, butyric acid can be produced in high yield by employing elevated pH.…”

“…An assessment of cell recycle technologies shows that centrifugation to remove cells can be cost-prohibitive and simple settling with or without the addition of flocculating agents requires large tanks due to the similarity in densities between cells and the fermentation broth. C. tyrobutyricum fermentation systems coupled with ultrafiltration or microfiltration have had limited investigation [16,17]. A complete cell recycle was used in Michel-Savin's work, recycling 100% of the cell mass back to the fermenter while removing all of the products.…”

“…A complete cell recycle was used in Michel-Savin's work, recycling 100% of the cell mass back to the fermenter while removing all of the products. A higher cell density was achieved, and as a consequence the productivity was considerably higher with more butyric acid formed [16,17]. However, total cell recycle is not preferred in long-term operation because of the accumulation of dead cells, which can easily block the membrane and prevent long-term production cycles; and oscillation in metabolic activities, which had been previously explained as aging of cell mass [25].…”

Rôle des bactéries sulfurogènes dans la corrosion du fer

“…En culture continue, la croissance d'une souche comme Desulfovibrio gabonensis DSM 10636 est possible jusqu'à un taux de dilution compris entre 0,16 et 0,20 h -1 sans accumulation de substrat carboné résiduel (Marchal, résultats non publiés). La croissance des bactéries sulfurogènes peut être limitée par l'effet inhibiteur exercé par les produits du métabolisme et notamment par l'H 2 S. Ce composé agirait, selon certains (Reis et al, 1992), par un découplage énergétique analogue à celui connu pour d'autres acides faibles (Herrero et al, 1985 ;Michel-Savin et al, 1990). Les acides faibles sous forme protonée ont, en effet, la propriété de traverser la membrane cellulaire par diffusion passive.…”

Batch and fed-batch production of butyric acid by Clostridium butyricum ZJUCB

“…Several anaerobic bacteria can produce butyric acid as the major end product during fermentation of sugars. Among them, Clostridium species have been used preferably for butyric acid production because they have many advantages over other species due to their simple medium requirement for cell growth and relatively high product yield (Michel-Savin et al, 1990a;1990b). Also, these strains can be readily isolated from soil, wastewater, animal digestion systems, contaminated dairy products, etc.…”