I. S. Maddox

Continuous production of acetone-butanol-ethanol using immobilized cells of Clostridium acetobutylicum and integration with product removal by liquid-liquid extraction

Abstract Cells of Clostridium acetobutylicum were immobilized by adsorption onto bonechar, and used in a packed bed or fluidized bed reactor for continuous production of ABE from whey permeate. At dilution rates in the range 0.35–1.10 h−1, ABE productivity values of 3.0 to 4.0 g/l·h were observed, but lactose utilization values were poor. When operated in an integrated system with product removal by liquid-liquid extraction, there was a decrease in productivity but lactose utilization was increased markedly. Of the three extractants tested, oleyl alcohol was superior to both benzyl benzoate and dibutyl phthalate.

The effect of the sugar source on citric acid production by Aspergillus niger

SummaryUnder otherwise identical fermentation conditions, the sugar source has been shown to have a marked effect on citric acid production by Aspergillus niger. Sucrose was the most favourable source, followed by glucose and fructose and then lactose. No citric acid was produced from galactose. Strong relationships were observed between citric acid production and the activities of certain enzymes in myccelial cell-free extracts prepared from fermentation samples. When sucrose, glucose, or fructose was the sugar source pyruvate carboxylase activity was high, but 2-oxoglutarate dehydrogenase activity was not detected. When galactose was the sugar source pyruvate carboxylase activity was low, but 2-oxoglutarate dehydrogenase activity was high. It is suggested that whereas glucose and fructose repress 2-oxoglutarate dehydrogenase, thereby causing accumulation of citric acid, galactose does not. The activity of aconitase showed a direct relationship to the citric acid production rate. Thus, the activity was highest when sucrose was the sugar source, and lowest when galactose was the source. It is suggested that when large amounts of citric acid are lost from the cell the activity of aconitase increases as a response to the diminished intracellular supply of its substrate.

The acetone-butanol-ethanol fermentation: recent progress in technology.

The acetone-butanol-ethanol (ABE) fermentation process, using Clostridium acetobutylicum or C. beijerinckii, epitomizes the problems of all fermentation processes vis-a-vis chemical synthesis. The purpose of this chapter is to review some recent developments in fermentation technology as applied to the ABE process. The aim of such technologies is to increase reactor productivity and/or remove product inhibition. In this way, the economics of the overall process can be improved

Continuous product recovery by in-situ gas stripping/condensation during solvent production from whey permeate usingClostridiumacetobutylicum

SummaryThe use of in-situ gas stripping for the removal of toxic butanol from a batch fermentation usingClostridiumacetobutylicum P262 has been examined. A cold trap was used to recover the butanol. Significant increases in the lactose utilization rate and solvents productivity were obtained.

Continuous solvent production from whey permeate using cells of Clostridium acetobutylicum immobilized by adsorption onto bonechar

Cells of Clostridium acetobutylicum were immobilized by adsorption onto bonechar and used in a packed bed reactor for the continuous production of solvents from whey permeate. A maximum solvent productivity of 4.1 g l−1 h−1, representing a yield of 0.23 g solvent/g lactose utilized, was observed at a dilution rate of 1.0 h−1. The reactor was operated under stable conditions for 61 days. High concentrations of lactose in the whey permeate favored solventogenesis, while low concentrations favored acidogenesis.

Use ofClostridiumacetobutylicum P262 for production of solvents from whey permeate

SummaryThe production of solvents from whey permeate in batch fermentation usingClostridiumacetobutylicum P262 was examined. An overall reactor productivity of 0.24 g/l.h was observed, representing a marked improvement over reports using other strains of clostridia. Using a semi-synthetic medium galactose was shown to be as effective a substrate as glucose. When whey permeate was used in which the lactose was hydrolysed prior to fermentation, preferential uptake of glucose over galactose was observed, and such hydrolysis provided no advantage to the fermentation process.

Production of n-butanol by fermentation of wood hydrolysate

SummaryThe production of n-butanol by fermentation of hydrolysates of Pinus radiata, using Clostridium acetobutylicum, has been investigated. Attempts to ferment the crude hydrolysate were unsuccessful. Pre-treatment of the hydrolysate by steam stripping followed by addition of activated carbon led to successful fermentation, but the treatment procedure caused unacceptable sugar losses. An alternative pre-treatment procedure using anion and cation exchange resins caused no such losses, and gave a butanol concentration after fermentation of 5·7 g/l, representing a yield of 17% based on sugar utilised.

Citric acid production by solid-state fermentation in a packed-bed reactor using Aspergillus niger

Kumara, a starch-containing root crop grown extensively in New Zealand, has been used as a substrate for citric acid production using Aspergillus niger in solid-state fermentation. When the process was operated in a packed-bed reactor, the bed loading was the most important operational parameter. The airflow rate and substrate particle size were also important but their net effects varied depending on other parameters; thus, a high airflow rate was conducive to citric acid production except under certain operating conditions (e.g., large substrate particle size) where it appeared to inhibit fungal growth possibly due to shear stress. A kinetic analysis of the system showed an overall reactor productivity of 0.82 g citrate kg−1 wet weight kumara h−1 which is twice that observed in flask culture. In this respect, the results in the packed-bed reactor were superior to published results in flask culture probably due to the improved aeration that was achieved.

In-line toxic product removal during solvent production by continuous fermentation using immobilized Clostridium acetobutylicum

Abstract Cells of Clostridium acetobutylicum were immobilized by adsorption onto bonechar, and used in a two-stage continuous reactor for solvent production from whey permeate. Gas-stripping (N 2 gas), an adsorbent resin (XAD-16) and a molecular sieve (silicalite) were evaluated for their use in between-stages solvent removal. All three techniques removed significant quantities of solvents, but not lactose, and allowed increases in sugar utilization and solvent productivity in the second stage. Gas stripping was the most successful technique, possibly because it removed only volatile solvents and not essential nutrients.

Production of n-butanol from whey filtrate using clostridium acetobutylicum N.C.I.B. 2951

SummarySulphuric acid whey filtrate has been shown to be a useful substrate for the production of n-butanol by fermentation. Using whey filtrate supplemented with 0.5% yeast extract, yields of 1.5%(w/v) n-butanol have been obtained. The ratio of butanol:acetone:ethanol products approximates 10:1:1.