Production of bioethanol by immobilized Saccharomyces Cerevisiae onto modified sodium alginate gel

Abstract

BACKGROUND: Microbial bioethanol production is an important option in view of the finite global oil reserves. Bioethanol fermentation was carried out using immobilized microorganisms (Saccharomyces cerevisiae, Zymomonas mobilis, Pichia stipitis, etc.), which has many advantages compared with the use of free cells. Various support materials have been used for bioethanol fermentation, and alginate gels have been one of the most widely used matrices for cell entrapment. The aim of this study was increased bioethanol production by Saccharomyces cerevisiae immobilized on alginate gels. First, N-vinyl-2-pyrrolidone was grafted onto sodium alginate. Then, the properties of ethanol production were investigated using the matrix obtained.

Mead production: fermentative performance of yeasts entrapped in different concentrations of alginate

“…The dry weight of the immobilized cells was determined by the same procedure as described previously for suspended cells in a medium. For assessing the growth of immobilized cells, after appropriate dilutions of liquefied beads, these were counted as the number of CFU in solid YPD plates, after incubation at 25 °C for 48 h. The immobilization yield was calculated as the immobilized dry weight of yeasts/immobilized and free dry weight of yeasts × 100 .…”

“…One of the most common methods of immobilization is the entrapment of cells in hydrogels, which involves entrapping living cells within a rigid network, which permits the diffusion of substrates and products, thereby making possible cell growth and the maintenance of active cells . Calcium alginate gels have been the most widely used matrices for cell entrapment owing to their simplicity . Alginate is a natural co‐polymer that is gelled when it comes into contact with bivalent cations such as Ca 2+ , forming beads .…”

Bioethanol Production Using Saccharomyces cerevisiae with Different Perspectives: Substrates, Growth Variables, Inhibitor Reduction and Immobilization

“…Also, several studies have been done to investigate new immobilizing agents that are cheap and easy to use ( Table 2). Yeast immobilization enhances ethanol productivity because-a) it reduces risk of contamination [33][34][35], b) it makes it easy to separate cell mass for the bulk liquid [36][37][38][39][40][41][42][43], c) it reduces production costs [18,36,42], d) biocatalyst can be recycled [43], e) fermentation time can be reduced [7,18], f) cells can be protected from inhibitors [44] g) more ethanol production compared to free cells [7,18,38,35]…”

Liquid–solid mass transfer behaviour of a fixed bed airlift reactor

“…The present study was conducted using a technique which involves the diffusion controlled dissolution of copper in acidified dichromate [29,30], the technique has been used widely to study liquid-solid mass transfer in view of its simplicity and accuracy [31][32][33][34][35]. The technique does not suffer from the drawback of the benzoic acid technique which produces exaggerated mass transfer coefficient owing to particle attrition, the present (1) Air-lift reactor, (2) nitrogen gas cylinder, (3) pressure regulator with screwdown valve, (4) calibrated rotameter, (5) 8 mm PVC tubing, (6) non-return valve, (7) G2 sintered glass gas sparger, (8) liquid level in the air-lift reactor, (9) riser, (10) downcomer, (11) insulated stainless steel support, (12) Raschig rings fixed bed, (13) insulated stainless steel strainer, (14) baffle, (15) drain valve.…”

“…Little has been done on the liquid-solid mass transfer behaviour of such reactors despite the importance of the subject in case of liquid-gas-solid catalytic reactions which are controlled by the liquid-solid mass transfer step. Such a study would assist in designing airlift bioreactors containing packed bed of immobilized enzyme catalyst and microorganisms used to conduct diffusion controlled bioreactions, such as the following examples: production of saccharides [8][9][10], bioethanol production [11][12][13][14][15][16], removal of phenols and other organic pollutants from wastewater [17][18][19][20][21][22], and removal of hexavalent chromium [23,24]. The present reactor can be used also to enhance the rate of mass transfer between the liquid reactant and the fixed enzyme even when air is not involved in the reaction, i.e.…”