Enhanced production of bioethanol and ultrastructural characteristics of reused Saccharomyces cerevisiae immobilized calcium alginate beads

Department of Wood Science and Landscape Architecture (BK21 Program), Chonnam National University, Gwangju 500-757, Republic of Korea.
Bioresource Technology (Impact Factor: 5.04). 09/2011; 102(17):8191-8. DOI: 10.1016/j.biortech.2011.06.063
Source: PubMed

ABSTRACT Yeast immobilized on alginate beads produced a higher ethanol yield more rapidly than did free yeast cells under the same batch-fermentation conditions. The optimal fermentation conditions were 30°C, pH 5.0, and 10% initial glucose concentration with 2% sodium alginate beads. The fermentation time using reused alginate beads was 10-14 h, whereas fresh beads took 24h, and free cells took 36 h. All bead samples resulted in nearly a 100% ethanol yield, whereas the free cells resulted in an 88% yield. Transmission electron microscopy (TEM) showed that the shortened time and higher yield with the reused beads was due to a higher yeast population per bead as well as a higher porosity. The ultrastructure of calcium alginate beads and the alginate matrix structure known as the "egg-box" model were observed using TEM.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Discarded carrots are a valuable source of biomass amenable for valorization. Their use as raw material for ethanol production by fermentation, using yeasts immobilized in Calcium alginate, was proposed. The biocatalyst immobilization method, the existence of internal and external mass transfer limitations, the effect of the initial pH and the reuse of immobilized yeasts were particularly evaluated. Results indicate that beads made with a 2 % solution of Sodium alginate and a 30 % solution of Saccharomyces cerevisiae were strong enough to allow an efficient nutrient transfer into the matrix and to prevent cell leaking. A stirring rate of 200 rpm was needed to avoid external mass transfer limitations. These beads were used in three successive fermentations. An initial pH of 5.5 reached the best fermentation parameters. Non-enriched, non-sterile carrot must was fermented through immobilized yeasts; and values of ethanol concentration (29.9 g L−1), Y p/s (0.409 g g−1), and productivity (7.45 g L−1 h−1) were obtained. These values were similar to those registered when free cells were used.
    12/2014; DOI:10.1007/s40095-014-0157-6
  • [Show abstract] [Hide abstract]
    ABSTRACT: Comparative studies of immobilized and free cells of Gibberella intermedia CA3-1 in bioconversion of 3-cyanopyridine to nicotinic acid were performed. Entrapping method was chosen based on the advantages in enzymatic activity recovery, mechanical strength and preparation procedure. Four entrapment matrices were investigated and sodium alginate was screened to be the most suitable material. Maximal nitrilase activity of alginate immobilized cells was obtained under conditions of 2 % alginate, 0.6 % CaCl2, 0.4 g cell/g alginate, 1.8 mm bead size. The immobilized cells showed excellent substrate tolerance even when the 3-cyanopyridine concentration was 700 mM. The half-lives of immobilized cells at 30, 40 and 50 °C were 315, 117.5 and 10.9 h, respectively, correspondingly 1.4, 1.6 and 1.7-fold compared with that of the free cells. Efficient reusability of immobilized cells up to 28 batches was achieved and 205.7 g/(g dcw) nicotinic acid was obtained with 80.55 % enzyme activity preserved.
    Bioprocess and Biosystems Engineering 07/2014; 38(1). DOI:10.1007/s00449-014-1258-6 · 1.82 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Large quantities of fruit waste are generated from agricultural processes worldwide. This waste is often simply dumped into landfills or the ocean. Fruit waste has high levels of sugars, including sucrose, glucose, and fructose, that can be fermented for bioethanol production. However, some fruit wastes, such as citrus peel waste (CPW), contain compounds that can inhibit fermentation and should be removed for efficient bioethanol production. We developed a novel approach for converting single-source CPW (i.e., orange, mandarin, grapefruit, lemon, or lime) or CPW in combination with other fruit waste (i.e., banana peel, apple pomace, and pear waste) to produce bioethanol. Two in-house enzymes were produced from Avicel and CPW and were tested with fruit waste at 12–15% (w/v) solid loading. The rates of enzymatic conversion of fruit waste to fermentable sugars were approximately 90% for all feedstocks after 48 h. We also designed a d-limonene removal column (LRC) that successfully removed this inhibitor from the fruit waste. When the LRC was coupled with an immobilized cell reactor (ICR), yeast fermentation resulted in ethanol concentrations (14.4–29.5 g/L) and yields (90.2–93.1%) that were 12-fold greater than products from ICR fermentation alone.
    Applied Energy 02/2015; 140. DOI:10.1016/j.apenergy.2014.11.070 · 5.26 Impact Factor