Evaluation of the waste from cassava starch production as a substrate for ethanol fermentation by Saccharomyces cerevisiae

Abstract

Cassava starch production waste (cassava pulp) has been proposed as a high potential ethanolic fermentation substrate due to its high residual starch level and the small particle size of the lignocellulosic fibers. Saccharification of the residual starch from a 3% (w/v) dry weight basis (DS) of cassava pulp by α-amylase (100°C, 10 min) and glucoamylase (60°C, 2 h) resulted in a glucose yield of 22.6 g/l [67.8% (w/w) DS of cassava pulp] and in lignocellulosic fibers at 0.5 g/g DS cassava pulp. Pretreatment of the lignocellulosic fiber with dilute sulfuric acid and calcium hydroxide at 121°C, 15 lb/in 2 for 30 min increased and decreased, respectively, its susceptibility to cellulase hydrolysis. Under the optimal conditions found, pretreatment of 6% (w/v) DS lignocellulosic fiber by 2% (w/v) H 2 SO 4 for 30 min, followed by saccharification by cellulase (40°C, 9 h), yielded a glucose level of 26.6 g/l [79.8% (w/w) DS of the cassava pulp]. The starch and lignocellulosic fiber hydrolysates obtained from 30 g cassava pulp and 60 g H 2 SO 4 pretreated lignocellulosic fiber were fermented by Saccharomyces cerevisiae, without the need for (NH 4 ) 2 SO 4 supplementation, to yield ethanol levels of 9.9 and 11.9 g/l, respectively, after 48 h.

Physicochemical treatment for improving bioconversion of cassava industrial residues

“…However, in the present study, the result was achieved in <5 h which includes pretreatment and hydrolysis process whereas the process took 72 h using unpretreated cassava pulp and enzyme cocktail [20]. Many studies have examined the use of hydrothermal as a pretreatment before enzymatic or acid hydrolysis and have reported high yields [29][30][31][32]. Fermentation inhibiting byproducts like furfural and HMF have been anticipated to be formed during the process involving high temperature and acid [33].…”

Ethanol Production from Sugarcane Leaves by Kluyveromyces marxianus S1.17, a Genome-Shuffling Mediated Transformant

“…The resulting slurry of acid-treated sugarcane leaves was filtered through stainless steel mesh and centrifuged to separate the acid-treated leaf hydrolysate (supernatant) from the acidtreated sugarcane leaves (residual solid). The glucose and xylose contents in the pretreatment hydrolysate were then analyzed by HPLC as reported (Akaracharanya et al 2011).…”

Characterization of xylose-utilizing yeasts isolated from herbivore faeces in Thailand

“…Single colony of yeast isolates grown on YX agar, pH 5.0 at 30°C, 48 h was inoculated into YX broth (50 ml in 250 ml Erlenmeyer flask), incubated at 30°C, 200 rpm for 24 h. The culture was transferred at 1% (v/v) into fresh YX broth (50 ml in 250 ml Erlenmeyer flask) and incubated at 30°C, 200 rpm for 24 h. The inoculum was inoculated at 10% (v/v) into the same medium and incubated at 30°C, 200 rpm for 24 h. After centrifugation at 4°C, 9793g (10 min), resultant supernatants were analysed for ethanol by gas chromatography 37 and for xylitol by high performance liquid chromatography (HPLC) 38 . S. stipitis JCM 10742…”