Enhanced production of bioethanol from waste of beer fermentation broth at high temperature through consecutive batch strategy by simultaneous saccharification and fermentation.

Malt hydrolyzing enzymes and yeast glycolytic and fermentation enzymes in the waste from beer fermentation broth (WBFB) were identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). A new 'one-pot consecutive batch strategy' was developed for efficient bio-ethanol production by simultaneous saccharification and fermentation (SSF) using WBFB without additional enzymes, microbial cells, or carbohydrates. Bio-ethanol production was conducted in batches using WBFB supernatant in the first phase at 25-67°C and 50rpm, followed by the addition of 3% WBFB solid residue to the existing culture broth in the second phase at 67°C. The ethanol production increased from 50 to 102.5g/L when bare supernatant was used in the first phase, and then to 219g ethanol/L in the second phase. The amount of ethanol obtained using this strategy was almost equal to that obtained using the original WBFB containing 25% solid residue at 33°C, and more than double that obtained when bare supernatant was used. Microscopic and gel electrophoresis studies revealed yeast cell wall degradation and secretion of cellular material into the surrounding medium. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) supported the existence of enzymes in WBFB involved in bioethanol production at elevated temperatures. The results of this study will provide insight for the development of new strategies for biofuel production.

Effects of glucuronic acid oligomers on the production, structure and properties of bacterial cellulose.

The addition of certain supplementary carbon sources to the culture media can influence the production, structural features and mechanical properties of bacterial cellulose (BC). In this study, different concentrations (0, 1, 2 and 4%) of a by-product, single sugar α-linked glucuronic acid-based oligosaccharide (SSGO), were added to the culture media during the production of BC. Production with 1% (BC1), 2% (BC2) and 4% (BC3) SSGO led to increases in BC production of 10.45, 12.74 and 9.01 g/L, respectively, after 10 days of cultivation under static conditions, while it was only 7.4 g/L when no SSGO was added (BC0). The structures of BC0, BC1, BC2, and BC3 were confirmed by XRD and FT-IR analysis. FE-SEM micrographs showed increased fibril thickness and decreased pore size in the SSGO added samples. The tensile strength of the BC0 was 16.73 MPa, while it was 25.05 MPa for BC1. However, with further increases in the concentration of SSGO, the tensile strength decreased to 20.76 and 19.77 MPa for BC2 and BC3, respectively. The results of this study provide further insight into the additive role of SSGO and improvement of the physico-mechanical properties of BC.

Potential of the waste from beer fermentation broth for bio-ethanol production without any additional enzyme, microbial cells and carbohydrates.

The potential of the waste from beer fermentation broth (WBFB) for the production of bio-ethanol using a simultaneous saccharification and fermentation process without any extra additions of saccharification enzymes, microbial cells or carbohydrate was tested. The major microbial cells in WBFB were isolated and identified. The variations in compositions of WBFB with stock time were investigated. There was residual activity of starch hydrolyzing enzymes in WBFB. The effects of reaction modes e.g. static and shaking on bio-ethanol production were studied. After 7 days of cultivation using the supernatant of WBFB at 30 °C the ethanol concentration reached 103.8 g/L in shaking culture and 91.5 g/L in static culture. Agitation experiments conducted at a temperature-profile process in which temperature was increased from 25 to 67 °C shortened the simultaneous process time. The original WBFB was more useful than the supernatant of WBFB in getting the higher concentration of ethanol and reducing the fermentation time. From this whole study it was found that WBFB is a cheap and suitable source for bio-ethanol production.