A green process for the production of butanol from butyraldehyde using alcohol dehydrogenase: process details

Abstract

Depletion of energy sources has drawn attention towards production of bio-butanol by fermentation.However, the process is constrained by product inhibition which results in low product yield. Hence, a new strategy wherein butanol was produced from butyraldehyde using alcohol dehydrogenase and NADH as a cofactor was developed. Butyraldehyde can be synthesized chemically or through fermentation. The problem of cofactor regeneration during the reaction for butanol production was solved using substrate coupled and enzyme coupled reactions. The conventional reaction produced 35% of butanol without regeneration of cofactor using 300 mM NADH. The process of substrate coupled reaction was optimized to get maximum conversion. NADH (30 mM) and 100 mg per ml of alcohol dehydrogenase (320 U mg À1 ) could convert 17.39 mM of butyraldehyde to butanol using ethanol (ratio of butyraldehye to ethanol 1 : 4) giving a maximum conversion of 75%. The enzyme coupled reaction under the same conditions showed only 24% conversion of butyraldehyde to butanol using the glutamate dehydrogenase-L-glutamate enzyme system for the regeneration of cofactor. Hence, substrate coupled reaction is suggested as a better method over the enzyme coupled reaction for the cost effective production of butanol.

Transient and Steady Pervaporation of 1-Butanol–Water Mixtures through a Poly[1-(Trimethylsilyl)-1-Propyne] (PTMSP) Membrane

“…Neither the feed concentration of 1-butanol nor temperature, time or the presence of yeast extract was found to substantially influence the separation factor of pervaporation (β) or selectivity (α) of the PTMSP membrane ( Figure 5). By comparing the average separation factor (β = 82) and selectivity (α = 2.6) and examining Equations (6,8,9), it follows that the organophilic pervaporation of the mixtures of 1-butanol with water appear to be positively influenced by the thermodynamic non-ideality of the solution to a significant extent. The separation factor and selectivity showed minor dependences on temperature, feed concentration and polymer aging (Figure 6).…”

“…For instance, the use of 1-butanol in the product portfolio of biorefineries has led to increased revenues in comparison to base scenarios, which can eventually help mitigate environmental impacts in economic terms [4]. Similar to ethanol, 1-butanol can be produced from renewable feedstocks by clostridial ABE fermentation [8][9][10][11], and separated from the medium by pervaporation. For example, pervaporation has been found to resolve the shortcomings membrane was fabricated by casting this solution onto a glass petri dish and the solvent was allowed to evaporate slowly over 3 days at room temperature.…”

Chaotropicity: a key factor in product tolerance of biofuel-producing microorganisms

“…Drawbacks include the challenge of maintaining enzyme activity during repeated cycles of fermentation and high cost of cofactors (though approaches have been employed to circumvent the latter) [94,204]. Exposure to chaotropic agents may have a greater effect on isolated enzymes than those in cells because the latter have chaperones to assist with refolding, and temperature increases can compound chaotropicity-induced inhibition of enzymes (see above).…”

Effect of embedded activated carbon nanoparticles on the performance of polydimethylsiloxane (PDMS) membrane for pervaporation separation of butanol

“…Biobutanol is commonly produced via the traditional acetone–butanol–ethanol (ABE) fermentation. However, there are significant challenges to overcome to make biobutanol an economically‐viable biofuel using fermentation such as the low final butanol concentration in the fermentation broth and the low productivity resulting from relatively low product concentration levels that become toxic for the microorganism . To improve the low butanol productivity in an ABE fermentation process, the in situ removal of the products via integrated recovery technologies, especially for butanol as the most toxic product from the fermentation broth, would lessen product toxicity and allow greater sugar conversion and higher productivity …”