Coculture fermentation of banana agro-waste to ethanol by cellulolytic thermophilic Clostridium thermocellum CT2

Abstract

Banana is a major cash crop of many regions generating good amount of waste after harvest. This agro waste which is left for natural degradation is used as substrate for single step ethanol fermentation by thermophilic, cellulolytic, ethanologenic Clostridium thermocellum CT2, a new culture isolated from elephant droppings. Scanning electron microscopic pictures clearly indicate cellulolysis and close interaction of selected isolate CT2 with cellulose. The optimum conditions for cellulose fermentation were 60°C, pH 7.5, inoculums size 5% and incubation time 5 days. Ethanol produced and reducing sugars were estimated by gas chromatography. Clostridium thermosaccharolyticum HG8 and Thermoanaerobacter ethanolicus ATCC 31937 were used in coculture fermentation with CT2. Coculture fermentation of CT2 with HG8 was more efficient in terms of ethanol production, cellulose degradation and reducing sugars utilization. A maximum ethanol yield of 0.41g/g substrate used was obtained on coculturing CT2 with HG8 on alkali treated banana waste. Coculture was active even at substrate concentrations up to 100 g/l, a maximum ethanol of 22 g/l was obtained at 100 g/l substrate concentration on coculturing CT2 with HG8. This is the first report on anaerobic single step conversion of banana waste to ethanol by C. thermocellum.

Valorization Potential of a Novel Bacterial Strain, Bacillus altitudinis RSP75, towards Lignocellulose Bioconversion: An Assessment of Symbiotic Bacteria from the Stored Grain Pest, Tribolium castaneum

“…The authors also mentioned that cocultivation was more effective for cellulose hydrolysis and reducing sugar production and bioconversion [101]. Similar to previous reports, we observed that co-culturing of B. altitudinis RSP75 and yeast significantly improves the rate of LC bioconversion and ethanol yield within a short duration of fermentation [102,103]. All of the above characteristics demonstrate the potential lignocellulolytic repertoire of B. altitudinis RSP75, and therefore encourage its further characterization for LC bioconversion.…”

Isolation and Identification of Yeast Strains From Sugarcane Molasses, Dates and Figs for Ethanol Production Under Conditions Simulating Algal Hydrolysate

“…Kalyani et al (2013) observed that the co-culture of S. cerevisiae and Pichia stipitis produced 23% and 38% more ethanol than the amounts produced by S. cerevisiae and P. stipitis in pure cultures. Harish et al (2010) obtained an ethanol yield of 0.41g.g -1 during the co-culture of Clostridium thermocellum and Clostridium thermosaccharolyticum on banana waste hydrolysate, namely 36 to 59% more than the corresponding pure culture of Clostridium thermocellum. These promising results show that coculture has great potential for efficient conversion of medium rich in salt, like green macro-algae (Chaetomorpha linum), to ethanol.…”

Biological hydrogen production using co-culture versus mono-culture system

“…[7] Another advantage is the combination of two processes into a single-step process by co-culture of two or more compatible microorganisms for cellulolytic hydrolysis and utilization of dissolved sugars for production of renewable energy for efficient processes. [73] The combination of facultative and anaerobic bacteria helped in eliminating the nitrogen-sparging step and shifted the metabolic pathways towards increased hydrogen production with a decrease in the by-product formation. [55] The advantage of using the co-culture system is that it not only improved the product yield, but also increased the biofilm formation as a potential feature in industrial fermentation system.…”