Detrimental effect of increasing sugar concentrations on ethanol production from maize or decorticated sorghum mashes fermented with Saccharomyces cerevisiae or Zymomonas mobilis

Abstract

The efficiency of ethanol fermentation, as affected by grain source (maize and decorticated red sorghum), total sugar concentration (13 or 20° Plato) and type of microorganism (Saccharomyces cerevisiae or Zymomonas mobilis) was studied. Maize mashes yielded 0.32 l ethanol kg(-1) ground grain whereas mashes prepared with decorticated red sorghum produced 0.28 l ethanol kg(-1). Both microorganisms yielded similar amounts of ethanol. However, high-gravity mashes (20° Plato) yielded lower amounts of ethanol compared to counterparts adjusted to 13° Plato (0.28 vs. 0.22 l ethanol kg(-1) ground grains). In decorticated sorghum mashes adjusted to 20° P, Z. mobilis produced 40 ml kg(-1) more ethanol compared to S. cerevisiae. In addition, Z. mobilis had a lower dependency on nitrogenous compounds.

Ethanol Production from Extruded Thermoplastic Maize Meal by High Gravity Fermentation with Zymomonas mobilis

“…The raw and extruded maize meals were liquefied with thermoresistant α -amylase (Liquozyme SC DS, Novozymes, Bagsvaerd, Denmark) according to previous investigations [ 5 , 18 ]. Then, hydrolyzates were saccharified with amyloglucosidase (Dextrozyme, Novozymes, Bagsvaerd, Denmark) in preparation for fermentation trials.…”

“…There is growing interest to develop several new technologies, especially through mechanical, chemical, and biological processes to optimize ethanol produced from maize [ 5 , 6 ]. An interesting approach is the implementation of thermoplastic extrusion, because it modifies starch to dextrose and lowers energy needs for high pressure steam.…”

“…In characterization studies, the initial sugar concentration is an important parameter for Z. mobilis growth; however, high glucose concentrations could induce inhibition ethanol production [ 18 ]. High gravity (HG) fermentation technology is used for industrial scale production of bioethanol.…”

Repeated batch fermentation of immobilizedE. coliexpressingVitreoscillahemoglobin for long-term use

“…It has been reported that nitrogen sources such as yeast extract or peptone enhance ethanol production in yeast. 41,42 These nitrogen sources also enhance sugar utilization for increased ethanol yield. [42][43] Yeast extract also supplies cofactors such as biotin and riboflavin for enhancement of ethanol yield.…”

Selection of Saccharomyces pastorianus variants with improved fermentation performance under very high gravity wort conditions

“…Recently, more attention has been paid to beer brewing with very high gravity (VHG) wort (18-25°P) due to its greater economic advantages. The VHG brewing can increase production efficiency and capacity, reduces energy, labor and capital costs, as well as improve beer smoothness and haze stability (Cooper et al 1998;Pérez-Carrillo et al 2011). However, yeast cells have to be exposed to higher osmotic stress and ethanol stress during VHG fermentation compared to the normal gravity fermentation (Pereira et al 2010).…”