Fermented Mash Research Articles

Production of a high concentration of ethanol from potato tuber by high gravity fermentation

To produce a high concentration of ethanol from viscous potato tuber mash, potato tuber mash containing high contents of solids (28%) was prepared by grinding the potato tuber without the addition of water. The viscosity of the potato mash was reduced by using Viscozyme (0.1%) at 50°C for 30 min. The potato mash was then liquefied using Liquozyme (0.1%) at 90°C for 30 min and optimal conditions for the simultaneous saccharification and fermentation (SSF) of the potato mash for ethanol production were investigated using statistical methods. Using 24 factorial design, saccharifying-enzyme and incubation temperature were found to be important factors. Using response surface methodology, the optimal saccharifying-enzyme dosage and incubation temperature were determined to be 1.45 AGU/g dry matter and 31.3°C, respectively. Under these optimal conditions for SSF, 14.92%(v/v) ethanol with 91.0% of theoretical yield was produced after 60 h, and all the starch was completely used up.

Real‐time monitoring of high‐gravity corn mash fermentation using in situ raman spectroscopy

In situ Raman spectroscopy was employed for real-time monitoring of simultaneous saccharification and fermentation (SSF) of corn mash by an industrial strain of Saccharomyces cerevisiae. An accurate univariate calibration model for ethanol was developed based on the very strong 883 cm(-1) C-C stretching band. Multivariate partial least squares (PLS) calibration models for total starch, dextrins, maltotriose, maltose, glucose, and ethanol were developed using data from eight batch fermentations and validated using predictions for a separate batch. The starch, ethanol, and dextrins models showed significant prediction improvement when the calibration data were divided into separate high- and low-concentration sets. Collinearity between the ethanol and starch models was avoided by excluding regions containing strong ethanol peaks from the starch model and, conversely, excluding regions containing strong saccharide peaks from the ethanol model. The two-set calibration models for starch (R(2) = 0.998, percent error = 2.5%) and ethanol (R(2) = 0.999, percent error = 2.1%) provide more accurate predictions than any previously published spectroscopic models. Glucose, maltose, and maltotriose are modeled to accuracy comparable to previous work on less complex fermentation processes. Our results demonstrate that Raman spectroscopy is capable of real time in situ monitoring of a complex industrial biomass fermentation. To our knowledge, this is the first PLS-based chemometric modeling of corn mash fermentation under typical industrial conditions, and the first Raman-based monitoring of a fermentation process with glucose, oligosaccharides and polysaccharides present.

A Fatal Case of CO2 Intoxication in a Fermentation Tank

Carbon dioxide (CO2 ) is an odorless constituent of air. Higher concentrations can be detected in geothermal and automotive emissions, fermentation, and sublimation of dry ice. An unskilled worker entered a fermentation tank to clean it, which had not been done for about 5months allowing for high concentrations of CO2 to build up. A second worker entered the tank to rescue the first one. Shortly after both were found the first worker was rescued directly whereas the tank had to be rotated to pull the second worker out. Cardiopulmonary resuscitation was successful only for the first worker. Medico-legal autopsy showed bruises, hematoma, myocardial hemorrhage, and edema of the lungs. The right lung was vacuum degassed in an argon atmosphere and quadrupole-mass-spectrometry showed an elevated CO2 content in lung gases. Thus, CO2 intoxication/asphyxia in a vitiated atmosphere due to fermentation of wine mash was established as the cause of death.

Research Regarding the Use of Wheat Biodiversity for Obtaining some Cereal-Based Fermented Mashes

Cereal-based fermented beverages are an opportunity to include probiotics and fiber in human nutrition. Nowadays, increasing the interest for rediscovering the benefits, on scientific basis, of traditional fermented beverages based on cereals. Fermented mashes based on different cereal grist, namely Braga in Romanian, is a healthy and nutritious beverage, a source for new functional products with beneficial effects on human health. Physical-chemical and sensorial characteristics of these beverages depend on the ingredients and method of preparation. In this article was analyzed the influence of the five varieties of wheat on the main physical-chemical and sensorial characteristics of the fermented mashes obtained from grounded debranned millet (Panicum miliaceum), different species of wheat (Triticum aestivum - two variety, Triticum durum - one varieties, Triticum spelta - one variety and Triticum turgidum - one variety) and well modified Pilsner barley malt. There have been two series of determinations: first series with ground millet with the disc mill set to 0.1 mm and a second series with ground millet with the disc mill set to 0.4 mm disc gap. For both series, the other grains used were milled to 0.4 mm disc gap. The mashes content is 1:12 = grounded mix (millet : wheat : barley malt = 1.33:1:1): water. After boiling, reconstruction of the initially content with water, filtering and adding of 7% w/w white crystalline sugar those two series of five sweet mashes was inoculated with a mixed culture (0,01% w/w - dry wheat beer yeast and 0,04% w/w - dry cheese lactic acid bacteria), incubated at 30 ºC for 15 h in the thermostat and then stored at 6ºC for 63 h. At beginning and follow-up of fermentation the mashes were analyzed (pH, volatile and total acidity, total and soluble dry substances, alcohol concentration and dynamic viscosity). At the end of fermentation, it was done the sensory evaluation (colour, sweet, sour, taste, texture and stability). All determinations have made in triplicate and data are shown as mean ± SD. The best results have obtained for mashes containing T. Spelta wheat, followed by mashes with T. durum variety. Highest dynamic viscosity and total acidity was recorded for mashes obtained with Triticum turgidum variety of wheat.

Simultaneous utilization of non-starch polysaccharides and starch and viscosity reduction for bioethanol fermentation from fresh Canna edulis Ker. tubers

Viscosity reduction and the effect of cell-wall degrading enzymes (CWDEs) were investigated using Canna edulis Ker. for bioethanol fermentation. The fermentation mash treated with CWDEs was much thinner (2.12Pas) than the control mash (8.42Pas), the fermentation efficiency was increased from 90.46% to 96.11%. HPLC analysis revealed that after treated with CWDEs, glucose and total sugar were increased by 28.07% and 7.60%, respectively. Changes in the starch granules were investigated by scanning electron microscopy (SEM), atomic force microscopy (AFM), and confocal laser scanning microscopy (CLSM). The results suggested that the reduction in viscosity was caused by changes in saccharide composition and physical changes of the starch granules. This present study is of significance that non-starch polysaccharides and starch can be simultaneously utilized for bioethanol production using roots and tubers as feedstock.

Cross-flow microfiltration of fermentation broth containing native corn starch

Cross-flow microfiltration of fermented mash containing native corn starch granules from a simultaneous saccharification and fermentation process, was investigated with respect to the process performance. Influence of transmembrane pressure and cross-flow velocity on normalized permeate flux rate decline and membrane fouling were examined. The microfiltration system was equipped with a tubular ceramic membrane with 0.45μm pore size. A combined pore-blockage–cake-filtration model was successfully used to determine the process performance and identify principal fouling mechanisms. Experimental results revealed that the fouling phenomenon taking place during microfiltration of the fermented mash follows a pattern of initial complete pore blockage and subsequent cake formation. As a result, initial rapid flux decline is followed by gradual flux decline. Fouled membranes were characterized using scanning electron microscopy (SEM). The membrane surface characteristics examined by SEM images evidenced formation of dense deposit on the upper membrane surface. Rinsing the fouled membrane with water followed by investigation of the permeate flux rate indicated occurrence of increased fouling, when microfiltration was carried out at high transmembrane pressure. The highest normalized flux decline was observed for microfiltration operated at the highest transmembrane pressure (1.4bar) and the lowest cross flow velocity (1ms−1). It is recommended to use high cross-flow velocity (4.55ms−1) and low transmembrane pressure (0.35bar) to minimize membrane fouling, triggered by components of the fermented mash.

Isolation and screening of microorganisms from a gari fermentation process for starter culture development

Cassava ( Manihot esculenta Crantz ), is used for the production of a variety of West African foods and ranks fourth in the list of major crops in developing countries after rice, wheat and maize. Gari is one of the most popular foods produced from cassava. Cassava may contain high levels of linamarin, a cyanogenic glucoside, which in its natural state is toxic to man. Therefore, some processing methods that can enhance the detoxification of cassava and lead to the improvement of the quality and hygienic safety of the food are vitally important for less toxic products to be obtained. Quality, safety and acceptability of traditional fermented foods may be improved through the use of starter cultures. There has been a trend recently to isolate wild-type strains from traditional products for use as starter cultures in food fermentation. A total of 74 bacterial strains and 21 yeast strains were isolated from a cassava mash fermentation process in a rural village in Benin, West Africa. These strains were assessed, together with 26 strains isolated at the Council for Scientific and Industrial Research (CSIR) from cassava samples sent from Benin previously, for phenotypic and technological properties. 24 presumptive lactic acid bacteria (LAB) were selected for further phenotypic, genotypic and technological characterization. Key words : Lactic acid bacteria, gari, cassava, fermentation.

Utilization of <i>Schizosaccharomyces pombe</i> for Production of Ethanol from Cane Molasses

The objective of the present study was using the molasses to produce ethyl alcohol by Schizosaccharomyces pombe as a fermenting microorganism and evaluation of the final product. Chemical and microbiological analyses were carried out for molasses samples which contained 49.9% soluble sugars. To produce ethanol the fermentation and distillation processes were controlled, and the results showed that optimum urea, sugar concentrations and the temperature were 0.25%, 20% and 32℃, respectively. This formulation gave 9.9% (w/v) ethanol in fermented mash while 11% (w/v) ethanol was produced using Saccharomyces cerevisiae as fermenting microorganism using similar production method. The physio- chemical characteristics of the ethanol which included purity, density and viscosity were 95.5%, 0.804 gm/ml and 0.81 cip, respectively, and the final ethanol appeared to be clear, bright and free from turbidity indicating its as high specification quality. The study recommended the utilization of both yeast Schizosaccharomyces pombe and Saccharomyces cerevisiae in large scale production of ethanol.

Ethanol biosynthesis and hydrocyanic acid liberation during fruit mashes fermentation

The biosynthesis of ethanol and release of hydrocyanic acid are important factors characterising the fermentation process of fruit mashes. The effects were determined of the fruit pretreatment and method of fermentation (with or without the addition of wine yeast) on the dynamics of ethanol biosynthesis and hydrocyanic acid liberation during fruit mashes fermentation and its concentrations in the spirits obtained. Depending on the fermentation variants, the highest rate of ethanol biosynthesis was observed between the first and third days of plum mashes fermentation, and between the first and fourth days of chokeberry mashes fermentation. In the majority of fermented mashes, the maximum dynamics of HCN liberation was recorded on the first day of the process. Spontaneous fermentation of fruit pulp resulted in much higher amounts of HCN in the spirits obtained (10.5 mg/l of plum spirit 40%, v/v, and 28.90 mg/l of chokeberry spirit 40%, v/v) in relation to the contents observed in the distillates from the mashes fermented with the addition of S. bayanus wine yeast (2.80 mg/l of plum spirit 40%, v/v, and 12.46 mg/l of chokeberry spirit 40%,v/v). The treatment with the pectolytic preparation (PEKTOZYME<sup>TM</sup> POWERMash) had no significant effect on the concentration of HCN in fruit spirits, whereas the pressure/thermal treatment reduced HCN content, especially in chokeberry distillate, by ca. 71% as compared to the reference spirit (obtained from raw pulp).  

An Evaluation of the Global Potential of Cocoyam (Colocasia and Xanthosoma species) as An Energy Crop

Aims: To evaluate the potential of cocoyam (Colocasia and Xanthosoma species) for the production of ethanol and methane for use as energy sources. Study design: Laboratory experimentation. Place and duration of study: Federal College of Agriculture Ibadan and Institute of Agricultural Research and Training (IAR&T), Moor Plantation, Ibadan, Nigeria between December 2010 and June 2011. Methodology: Five, 15, 25 and 35 kg samples of peeled cocoyam corms were weighed in three replicates. Next, the weighed cocoyam was soaked in clean water for 24 hr, and afterwards placed on a clean tray and allowed to air dry naturally for 4 hr. The cocoyam corms were then cut and the pieces transferred to a mortar where they were mashed to attain sufficient size reduction. The mash was then transferred into a plastic bucket. Five hundred, 650, 800 and 950 ml of N-hexane (C6H14) was added to the 5, 15, 25 and 35kg samples. The mash was thoroughly stirred to achieve an even mixture with the hexane. It was then covered and left undisturbed in the laboratory at room temperature for 8 days. The fermented mash was poured onto a 0.6 mm aperture size sieve and completely squeezed to dryness while the liquid filtered through the sieve. N-hexane was removed from the filtered liquid. The collected liquid was poured into a glass dish and then gradually heated at 79°C for a total of 10 hr (at intervals of 2 hr heating followed by 1 hr cooling) to ensure complete evaporation of any trapped H2O or CO2 remaining in it. Afterwards the final liquid (ethanol) was allowed to cool normally in the lab and its mass, volume and other properties were measured. Results: It was found that ethanol was yielded at the rate of 139 L/tonne of cocoyam. Therefore, 10 million tonnes annual global production of cocoyam is potentially able to Research Article British Journal of Applied Science & Technology, 2(1): 1-15, 2012 2 produce 331 million gallons of ethanol (i.e. 200 million gallons gasoline equivalent) or 39.5 million cubic metres of methane which on burning would produce 179.3 x 10 MJ of energy. The mash obtained as byproduct of the processes is capable of supplying 59 calories of food energy per 100g. Conclusion: Cocoyam has very good potential as a source of ethanol and methane. Its use as a renewable source of energy for the production of biofuels is recommended and doing so poses no threat to the environment or food supply. The mash produced is an excellent feedstock for livestock. The scientific innovation and relevance of this study lies in the fact that cocoyam is a renewable produce and the fermentation and anaerobic digestion methods used are applicable across countries and regions irrespective of available degree of industrialization and climate.

Basic Physical-Chemical and Sensorial Evaluation of Some Fermented Mashes Produced from Wheat, Husked Millet, Barley Malt and Oat

Fermented mashes based on different cereal grist are a healthy and nutritious beverage, a source for new functional products with beneficial effects on human health. These mashes are a thick consistency and sour-sweet taste, different colors depending on the ingredients and method of preparation. In this study were determined the main physical and chemical characteristics (pH, volatile and total acidity, total and soluble dry substances, alcohol concentration, dynamic viscosity) and was made sensorial analysis of some boiled aqueous mashes obtained from wheat, husked millet, barley malt and oat. Mashes were fermented at 30°C with a mixed culture of mesophilic cheese lactic acid bacteria and wheat beer yeast for 23h, followed by a cold maturation at 4°C for 42h. This study allows exploring the potential of different cereals to produce cereal-based beverages. The best results were obtained for mashes containing a larger amount of barley malt, followed by mashes with oat. Highest dynamic viscosities were recorded for mashes obtained only from wheat and millet. All determinations were made in triplicate and data were shown as mean ± SD.

The Fate of Aflatoxin in Corn Fermentation

A lab-scale ethanol fermentation was investigated to determine where aflatoxin concentrated during each phase of production. Four corn samples with high levels of aflatoxin (ranging from 7750 – 17,208 parts per billion) and their replicates were compared with a replicated negative control. Fractions were taken from the fermented mash, distilled ethanol, stillage, and dried corn solids (DCS). These fractions were analyzed using two different immunoassay methods and liquid chromatography tandem mass spectrometry (LC-MS/MS). Results indicated no aflatoxin was found in the distilled ethanol. Some aflatoxin (13%) was detected in the stillage, but most of the toxin was recovered in the DCSs ranging from 31% to 58%. A second series of experiments were conducted to investigate the effect of binders on dried distillers grains (DDGs). A brewers dried yeast anti-caking binder that contains glucomannon (MTB-100?), was mixed with contaminated DDGs. Addition of the binder showed a significant reduction in aflatoxin levels in comparison to a positive control. Aflatoxin binding at 2% binder w/w reached 72.5% and showed a minimal binding percentage increase of 80% at 6% binder w/w. Testing was also conducted to determine if environmental variables such as pH and temperature had any effect on the binding capabilities. Temperature near 0?C resulted in binding at 19.7% at a pH range of 6 to 8. Additionally, at a temperature of 40?C resulted in binding of 36%, 47%, and 45% at pHs 6, 7, and 8, respectively. These findings suggest that the addition of sorbents may be an effective way of salvaging contaminated DDGs.

Relationship among Amylose Content, Starch Pasting and Ethanol Fermenta-tion in Sweetpotato Varieties for Starch Use

Fifteen starch-based sweetpotato varieties were used to test amylose contents (AC), starch pasting properties and ethanol fermentation characteristics, and analyze the difference and relationship among them. The results indicated that there were significant differences among dry matter content, starch content and AC of different sweetpotato varieties, and AC was significantly correlated to dry matter content and starch content. Differences presented among pasting properties in different varieties of sweetpotato, and the relationship among RVA eigenvalues was close. There were significant differences among ethanol fermentation characteristics of different sweetpotato varieties, and ethanol content was significantly correlated to fermen-tative strength. There were no significant correlation between AC and RVA eigenvalues, but pasting temperature (PT) was posi-tively correlated to dry matter content (r=0.661, P0.01) and starch content (r=0.670, P0.01). AC was positively correlated to ethanol content (r=0.653, P0.01) and fermentative strength (r=0.698, P0.01), but not significantly correlated to fermentation efficiency and fermented mash viscosity. Fermented mash viscosity was negatively correlated to breakdown value (BDV) (r= –0.563, P0.05) and positively correlated to setback value (SBV) (r=0.639, P0.05), but ethanol content, fermentation efficiency and fermentative strength were not significantly correlated to RVA eigenvalues. The cluster analysis showed that 15 varieties were divided into three parts: the first part featured higher AC and BDV, the second part had the highest AC and the lowest BDV, and the third part had the lowest AC and the highest BDV. Consequently, AC and BDV could be used as the indexes to evaluate the ethanol fermentation characteristics of sweetpotato, and the sweetpotato with higher AC and BDV was the breeding targets for fuel ethanol.

Protein Enrichment of Irish potato (Solanium tuberosium) peels through Solid Substrate Fermentation by Saccharomyces cerevisiae and Aspergillus Niger

Flour prepared from dried potato peels were inoculated with pure strains of either Aspergillus niger or Saccharomyces cerevisiae and then left to ferment for seven days. Chemical analysis of the fermented peel mash revealed a significant (P< 0.05) increase in the crude protein content (13.62%) of the potato peel mash when compared with the unfermented potato peel (10.50%).The result also shows that fermentation increased significantly the crude protein, ash, lipid and fibre contents of the fermented potato peel mash, while a decrease in carbohydrate was observed. Moisture concentration of 125%, temperature of 30 O C and 25 O C and a pH of 3.5 and 5.5 were found to be optimum for the growth of A. niger and S. cerevisiae on the mash. Increase in all mass resulting from the growth of the two fungi contributed to the resultant increase in the crude protein content of the fermented mash. The fermented peels could therefore be a good source of cheap protein enriched feed. Keywords - Potato peels; Fermentation; Crude Protein content; Fungi.

Distiller’s dried grains with solubles as an alternative protein source in diets of tilapia

AbstractDistiller’s dried grains with solubles (DDGS), a dried residue that remains after the fermentation of grain mash by selected yeasts and enzymes to produce ethanol and carbon dioxide, is currently readily available and less expensive than other conventional protein sources on a per unit protein basis. The nutrient content and nutritional value of DDGS varies with the source and quality of the grains, fermentation time and efficiency, the drying process and the quantity of distiller’s solubles added. In general, corn and wheat DDGS are deficient in lysine and methionine for tilapia, with lysine being the most limiting. Research evaluating the nutritional value of DDGS showed that 20–30% DDGS derived from corn or wheat can be included in tilapia diets without requiring lysine supplementation. With supplementation of lysine, DDGS at levels of 40% or higher can be used without affecting growth performance and feed utilization efficiency. Distiller’s dried grains with solubles also contain yeast, a rich source of beta glucan and nucleotides that have been reported to enhance immunity and disease resistance in fish. Corn DDGS, owing to its high oil content, is rich in linoleic acid and is an excellent source of energy and essential fatty acids for tilapia. High concentrations of xanthophylls present in corn DDGS may impart yellow pigment in fish flesh if included at high levels. Taking into consideration various factors affecting the nutritional value of diets and the quality of pellet and fish products, 15–20% DDGS appears to be optimum in the diets of tilapia.

Effect of rehydration and fermentation methods on the quality of garri produced from stored cassava chips

Garri was produced from cassava chips stored over 3 months by milling the chips before rehydration and mash fermentation by the traditional method (MRT) or backslopping (MRB). Chips were also rehydrated before milling, fermented traditionally (RMT) and then roasted, while garri from fresh cassava tubers fermented traditionally served as control (C). The garri samples were evaluated for pH, cyanide content and sensory acceptability. Garri produced from chips by the RMT method gave pH values of 4.25 on month 0 and increased to 4.91 after 3 months; MRT and MRB decreased from 3.42 to 2.91 and 3.36 to 3.13 respectively. The control garri had a pH of 3.83. The cyanide content of control garri was 100.8 mg/kg; RMT ranged from 67.44 to 65.28 mg/kg; MRT, 79.20 to 67.88 mg/kg and MRB, 72.00 to 56.88 mg/kg. Sensory rating indicated that RMT garri were best accepted within the first 2 months during which they also had the highest pH and the lowest cyanide content. MRB garri was most accepted at the third month; it had intermediate pH values while the cyanide content was lowest at the second and third months. Key words: Cassava chips, rehydration, fermentation, garri, pH, cyanide content, sensory attributes.

식음료폐기물을 이용한 바이오에탄올 생산

Because beverage waste contains a lot of sugar, it can be used as a valuable resource for energy. But beverage waste is discharged through the water treatment. To prevent the waste of the energy resource, we produced bioethanol by using beverage waste in this study. In order to produce bioethanol, we added distillers stillage and NaOH for fermentation condition (nutrients and pH adjustment). As a results, ethanol concentration was 5.92 vol%. In contrast, ethanol concentration of blank (not added nutrients) was low and fermentation rate was very slow. Because components of the distillers stillage help the yeast growth, fermentation yield and rate was improved. Finally, we operated distillation and dehydration process by using fermented mash and produced fuel bioethanol (more than 99.5 wt%). We think that this results may provide useful information with application of commercial ethanol production using beverage waste.

The Influence of The Degree of Grinding to Obtain of Some Fermented Mashes Based on Whole Wheat and Husked Millet

The purpose of this article was to study the influence of degree of milling whole wheat (was ground in 4 variants of grain) and husked millet (was finely ground) to obtain fermented mashes type Braga. There have been 4 mashes of grist of whole wheat, grist husked millet, hop pellets and water and were boiled under continuous stirring and then cooled. Their content has diluted with water and then strainer by pressed through a sieve. Each mash-filtrate has divided in two and added white sugar 7%, resulting two series of sweet mashes. One has inoculated with a mixed culture of yeast and lactic bacteria and the other only with yeast culture. After fermentation were analyzed fermented mashes (pH, volatile and total acidity, total and soluble dry substances, dynamic viscosity, alcohol concentration, number of yeast and bacteria cells (UFC/mL). All determinations have made in triplicate. For both series of fermented mashes observed an increase in viscosity for increasing grain particles of grist. Increased viscosity was higher when using only inoculums of yeast culture. pH values for both series of mashes varied in opposite directions. Towards lower pH's initial pH was significant for the series of mashes fermented with mixed cultivation of microorganisms. Are balanced values of alcoholic strength of fermented mashes at 25°C for 40 h. Very small inoculums of yeast ensures appropriate alcohol concentration, but not a total acidity that provides drinking fermented sour-sweet character type specific Braga. According to the ingredients used and method of obtaining of fermented mashes recommended wheat grain milling at 0.3 and/or 0.4 mm for a positive sensory evaluation.

Protein Improvement in Gari by the Use of Pure Cultures of Microorganisms Involved in the Natural Fermentation Process

The ability of microorganisms involved in cassava mash fermentation to produce and improve protein value by these microorganisms during fermentation was studied. Standard microbiological procedures were used to isolate, identify and determine the numbers of the organisms. Alcaligenes faecalis, Lactobacillus plantarum, Bacillus subtilis, Leuconostoc cremoris, Aspergillus niger, A. tamari, Geotrichum candidum and Penicillium expansum were isolated and identified from cassava waste water while standard analytical methods were used to determine the ability of the isolates to produce linamarase and the proximate composition, pH and titrable acidity of the fermenting mash. The linamarase activity of the isolates ranged from 0.0416 to 0.2618 micromol mL(-1) nmol(-1). Bacillus subtilis, A. niger, A. tamari and P. expansum did not express any activity for the enzyme. Protein content of mash fermented with mixed fungal culture had the highest protein value (15.4 mg/g/dry matter) while the raw cassava had the least value (2.37 mg/g/dry matter). The naturally fermented sample had the least value for the fermented samples (3.2 mg/g/dry matter). Carbohydrate and fat contents of naturally fermented sample were higher than values obtained from the other fermented samples. Microbial numbers of the sample fermented with mixed bacterial culture was highest and got to their peak at 48 h (57 x 10(8) cfu g(-1)). pH decreased with increase in fermentation time with the mash fermented by the mixed culture of fungi having the lowest pH of 4.05 at the end of fermentation. Titrable acidity increased with increase in fermentation time with the highest value of 1.32% at 96 h of fermentation produced by the mixed culture of fungi. Thus fermentation with the pure cultures significantly increased the protein content of mash.

Simultaneous saccharification and continuous fermentation of sludge-containing mash for bioethanol production by Saccharomyces cerevisiae CHFY0321

A continuous process was employed to improve the volumetric productivity of bioethanol production from cassava mash containing sludge and to simplify the process of ethanol production from cassava. After raw cassava powder was liquefied, it was used directly in a continuous process without sludge filtration or saccharification. A fermentor consisting of four linked stirrer tanks was used for simultaneous saccharification and continuous fermentation (SSCF). Although the mash contained sludge, continuous fermentation was successfully achieved. We chose the dilution rate on the basis of the maximum saccharification time; the highest volumetric productivity and ethanol yield were observed at a dilution rate of 0.028 h⁻¹. The volumetric productivity, final ethanol concentration, and % of theoretical ethanol yield were 2.41 g/Lh, 86.1g/L, and 91%, respectively. This SSCF process using the self-flocculating yeast Saccharomyces cerevisiae CHFY0321 illustrates the possibility of realizing cost-effective bioethanol production by eliminating additional saccharification and filtration processes. In addition, flocculent CHFY0321, which our group developed, showed excellent fermentation results under continuous ethanol production.