Ethanol production from concentrated food waste hydrolysates with yeast cells immobilized on corn stalk

Abstract

The aim of the present study was to examine ethanol production from concentrated food waste hydrolysates using whole cells of S. cerevisiae immobilized on corn stalks. In order to improve cell immobilization efficiency, biological modification of the carrier was carried out by cellulase hydrolysis. The results show that proper modification of the carrier with cellulase hydrolysis was suitable for cell immobilization. The mechanism proposed, cellulase hydrolysis, not only increased the immobilized cell concentration, but also disrupted the sleek surface to become rough and porous, which enhanced ethanol production. In batch fermentation with an initial reducing sugar concentration of 202.64 ± 1.86 g/l, an optimal ethanol concentration of 87.91 ± 1.98 g/l was obtained using a modified corn stalk-immobilized cell system. The ethanol concentration produced by the immobilized cells was 6.9% higher than that produced by the free cells. Ethanol production in the 14th cycle repeated batch fermentation demonstrated the enhanced stability of the immobilized yeast cells. Under continuous fermentation in an immobilized cell reactor, the maximum ethanol concentration of 84.85 g/l, and the highest ethanol yield of 0.43 g/g (of reducing sugar) were achieved at hydraulic retention time (HRT) of 3.10 h, whereas the maximum volumetric ethanol productivity of 43.54 g/l/h was observed at a HRT of 1.55 h.

Glucoamylase production from food waste by solid state fermentation and its evaluation in the hydrolysis of domestic food waste

“…To produce lactic acid from FW, Sakai et al (2004) used glucoamylase to saccharify the production medium. In other studies, commercial glucoamylase, alpha-amylase and cellulase solutions were used to saccharify the kitchen wastes for ethanol production Uncu and Cekmecelioglu, 2011;Yan et al, 2012). If the enzymes could be produced in situ without downstream treatments and integrated with the biochemicals production, the cost of the process would be decreased (Merino and Cherry, 2007;Wang et al, 2010).…”

Bioethanol from Dried Household Food Waste Applying Non-isothermal Simultaneous Saccharification and Fermentation at High Substrate Concentration

“…Productivities as high as 24-49.88 g/L/h have been reported during fermentation of FW hydrolyzates by free or immobilized yeast cells in continuous systems [34,36,37].…”

“…Higher ethanol production was obtained by Yan et al [35], (81.50 g/L) when fermented a FW hydrolyzate contained 163.22 g/L reducing sugar in a batch mode by free yeast cells. Immobilization of yeast cells in calcium alginate gel or modified corn stalk resulted in 89.28 and 87.91 g/L ethanol production respectively from a concentrated FW hydrolyzate (approximately 200 g/L reducing sugar) [36,37].…”

Utilization Of Household Food Waste For The Production Of Ethanol At High Dry Material Content

“…This way, increasing pubic concerns about utilizing food sources for the production of biofuels can be solved, as the utilization of either sugars or corn for the production of biofuels have contributed to the increase of their price worldwide, resulting in severe problems for the poorer countries. All these concerns led to a rapid increase in research to utilize low-cost by-products and wastes as raw material [3][4][5][6]. Lignocellulosic biomass represents great potential to be utilized as raw material due to the high amounts produced every year [7], and can be derived from woody or agricultural residues such as wheat straw, corn cobs, bagasse, rice straw, et cetera.…”