Semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast

Summary A mathematical model is proposed to explain the influence of the volume fraction of inoculum on the fermentation time and ethanol productivity in semicontinuous ethanol fermentation of sugar cane blackstrap molasses by pressed yeast.Nomenclature a, b, c, d constants, see equation (5) - E_o initial ethanol concentration - E_f final ethanol concentration - K₁, K₂, K₃ constants, see equation (1) - P ethanol productivity - P_c calculated values of P - P_e experimental values of P - r correlation coefficient - S_o initial TRS concentration - S_m TRS concentration of the feeding mash - T fermentation time (average of the experimental values) - T_c calculated value of T - T_e experimental value of T - TRS total reducing sugars calculated as glucose - U_o initial urea concentration - U_m urea concentration of the feeding mash - V reactor working volume - V_i volume of the inoculum - volume fraction of inoculum=V_i/V     

Ethanolic fermentation of cane molasses by a highly flocculent yeast

Summary A study of the comparative kinetics of standardS.uvarum ATCC 26602 withS.cerevisiae Y-10 (an isolate) and a highly flocculent strain ofS.uvarum in batch mode has shown that both the isolate and the highly flocculentS. uvarum strain have more desirable characteristics than the standard strains for ethanol production from cane molasses.     

Continuous high-ethanol fermentation from cane molasses by a flocculating yeast

Repeated-batch fermentation by a flocculating fusant, Saccharomyces cerevisiae HA 2, was done in a molasses medium that contained 20% (w/v) total sugar, at 30°C in an automatically controlled fermentor, and the effects of ethanol concentration on the specific growth rate and the specific production rate of ethanol were studied. Both the specific growth rate and the specific production rate of ethanol fell with increase of ethanol concentration, and there was a linear correlation between each rate and the concentration of thanol. The maximum specific growth rate (μ_max) and the maximum specific production rate of ethanol (q_max) were 0.12 h⁻¹ and 0.1 g ethanol/10⁹ cells·h, respectively. The specific growth rate and the specific production rate of ethanol fell to zero at ethanol concentration of 89 g/l and 95 g/l, respectively. The number of viable cells, calculated from the linear inhibition equation, was 1.3 × 10⁹ cells/ml for production of 85 g/l ethanol at a dilution rate (D₁) of 0.2 h⁻¹. Based on this estimation, a laboratory-scale continuous fermentation, using two fermentors in series, was done. In the second fermentor, 85 g/l ethanol was produced at a dilution rate (D₁) of 0.2 h⁻¹ by the active feedig of the fermented mash from the first fermentor into the second fermentor by pumping (hereafter called active feeding). To maintain the number of viable cells above 10⁹ cells/ml in the second fermentor, a active feeding ratio of more than 23% was required. Under these conditions, 81 g/l ethanol was produced in the second fermentor at a dilution rate (D_t) of 0.25 h⁻¹, and the high ethanol productivity of 20.3 g/l·h could be achieved. A bench-scale continuous fermentation, using two fermentors in series, with a active feeding ratio of 25% was done. An ethanol concentration of 84 g/l in the second fermentor at a dilution rate (D_t) of 0.25 h⁻¹ was achieved, just as it was in the laboratory-scale fermentation test.     

Studies on continuous ethanol fermentation of sugar cane molasses

Summary A new laboratory system for continuous fermentation is described. It is well suited for fermenting concentrated substrates such as moderately dilute molasses. A rotating microporous filter, which is annexed to the fermentor vessel, allows the free escape of metabolic products while retaining yeast in the fermentor.The slop is recirculated after removal of ethanol by distillation leading to a build-up of non-fermentables. The concentration of these and of yeast cells is checked by a controlled bleed. The described system is a useful tool for small-scale experiments on continuous ethanol fermentation.     

Pilot-scale multi-stage multi-feeding continuous ethanol fermentation using non-sterile cane molasses

Summary Non-aseptic fermentation of a 28 brix cane molasses solution was successfully carried out in a pilot-scale 5-stage multi-feeding continuous system for 30 days. The effluent ethanol concentration, overall volumetric productivity and sugar conversion yield averaged 8.54 % (v/v), 5.35 g/L-hr and 92.4 % of theoretical, respectively.     

Enhanced ethanol production by continuous fermentation in a two-tank system with cell recycling

An experimental method for producing ethanol continuously was designed and tested with a cell-recycling two-tank system, which was composed of two fermentors, each of which was individually equipped with a settler for recycling flocculent yeast. This system was effective for the continuous fermentation of ethanol from sucrose at high cell-recycling (r = 0.8–0.9) and dilution (up to 0.48 h^?1) rates. The system has several advantages; the high cell concentration in the fermentors and relief of substrate and product inhibition. Thus, the enhanced productivity using this continuous fermentation with the two-tank cell-recycling system was significantly higher compared with that of the batch fermentation. The results indicate that increased recycling ratios caused an increase in biomass concentration and subsequently, product concentration in the tank. The ethanol productivity increased with the dilution rate, but higher dilution rates could render increasing amounts of sugar unconverted. Continuous fermentation with the sugar feed concentration of 160 g/l at r = 0.9 and dilution rate of 0.2 h^?1 achieved the highest productivity with less than 2% of the unconverted sugar in the product steam. Under the same cell recycling ratios a productivity range of 6.9–7.5 g/l h^?1 could be achieved with feeding concentrations of 80–200 g/l, while batch fermentation at these sugar concentrations led to productivities of 3.85–4.48 g/l h^?1.     

Effects of yeast invertase on ethanol production in molasses

Ethanol fermentation by an alcohol yeast, YOY655, was slower in molasses than in a nutrition rich medium with the same sugar content. Osmolality was much higher in the molasses, and the slower fermentation in the molasses was ascribed to depressed fermentation under the high osmotic pressure. Yeast invertase was an important factor in regulation the osmolality and the fermentation rate in the molasses.     

The use of tamarind waste to improve ethanol production from cane molasses

Tamarind wastes such as tamarind husk, pulp, seeds, fruit and the effluent generated during tartaric acid extraction were used as supplements to evaluate their effects on alcohol production from cane molasses using yeast cultures. Small amounts of these additives enhanced the rate of ethanol production in batch fermentations. Tamarind fruit increased ethanol production (9.7%, w/v) from 22.5% reducing sugars of molasses as compared to 6.5% (w/v) in control experiments lacking supplements after 72 h of fermentation. In general, the addition of tamarind supplements to the fermentation medium showed more than 40% improvement in ethanol production using higher cane molasses sugar concentrations. The direct fermentation of aqueous tamarind effluent also yielded 3.25% (w/v) ethanol, suggesting its possible use as a diluent in molasses fermentations. This is the first report, to our knowledge, in which tamarind-based waste products were used in ethanol production. Received 2 April 1998/ Accepted in revised form 13 November 1998     

Production of ethanol from sugar cane molasses by Zymomonas mobilis

Summary Zymomonas mobilis strains were compared with each other and with a Saacharomyces cerevisiae strain for the production of ethanol from sugar cane molasses in batch fermentations. The effect of pH and temperature on ethanol production by Zymomonas was studied. The ability of Z. mobilis to produce ethanol from molasses varied from one strain to another. At low sugar concentrations Zymomonas compared favourably with S. cerevisiae. However, at higher sugar concentrations the yeast produced considerably more ethanol than Zymomonas.     

一株拜氏梭菌利用甘蔗废糖蜜发酵生产丙酮丁醇

以甘蔗废糖蜜作为原料,利用Clostridium beijerinckii DSM 6422菌株进行丙酮丁醇发酵的初步研究.结果表明:采用H2SO4预处理糖蜜,初糖质量浓度60 g/L,(NH4)2SO4 2g/L,CaCO3 10 g/L,温度30℃,pH 5.5～7.0,接种量6％(体积分数),在5L发酵罐中发酵培养96 h,总溶剂产量为16.17 g/L,其中丁醇质量浓度为10.07 g/L,总溶剂产率为30.2％,糖利用率为89.3％.     

Top and bottom yeasts together accelerate ethanol production in molasses fermentation

Summary Alcohol producing top and bottom yeasts were employed individually and together to assess their role in enhancing the rate of ethanol production, in cane molasses fermentation, at 30°C. The combination of top yeastS.cerevisiae NCIM 3281, and bottom yeastS.uvarum NCIM 3509, improved the enthanol production rate by 32.6% in batch fermentation and 25.2% in recycling yeasts cell fermentation as compared to their mean value of individual ethanol production activity.     

Influence of exponentially decreasing feeding rates on fed-batch ethanol fermentation of sugar cane blackstrap molasses

Summary The ethanol yield was not affected and the ethanol productivity was increased when exponentially decreasing feeding rates were used instead of constant feeding rates in fed batch ethanol fermentations. The influences of the initial sugar feeding rate on the ethanol productivity, on the constant ethanol production rate during the feeding phase and on the initial ethanol production specific rate are represented by Monod-like equations.Nomenclature F reactor feeding rate (L.h^–1) - F_o initial reactor feeding rate (L.h^–1) - K time constant; see equation (l) (h^–1) - M_E mass of ethanol in the fermentor (g) - M_s mass of TRS in the fermentor (g) - M_x mass of yeast cells (dry matter) in the fermentor (g) - P ethanol productivity (g.L^–1.h^–1) - R ethanol constant production rate during the feeding phase (g.h^–1) - s standard deviation - S_o TRS concentration in the feeding mash (g.L^–1) - t time (h) - T fermentor filling-up-time (h) - T time necessary to complete the fermentation (h) - TRS total reducing sugars calculated as glucose (g.L^–1) - V_o volume of the inoculum (L) - V_f final volume of medium in the fermentor (L) - X_o yeast concentration of the inoculum (dry matter) (g.L^–1) - ethanol yield (% of the theoretical value) - initial specific rate of ethanol production (h^–1)     

利用甘蔗糖蜜发酵生产花生四烯酸的研究

通过培养高山被孢霉利用糖蜜来发酵生产花生四烯酸(ARA),研究了不同甘蔗糖蜜预处理方法对ARA发酵生产的影响。研究表明:H2SO4法是最利于ARA发酵生产的糖蜜预处理方法。利用预处理的甘蔗糖蜜发酵生产ARA,通过单因素实验设计,确定了最优的培养条件,包括初始还原糖80 g/L,N源6 g/L,接种量20%,初始pH6.0和培养温度25℃,在此条件下发酵,干细胞质量、油脂含量、ARA产量和糖利用率分别达到28.5 g/L、11.7g/L、3.68 g/L和94.5%。     

响应面法优化甘蔗糖蜜发酵产丁醇

以甘蔗糖蜜为底物,用响应面法对高丁醇比突变菌株拜氏梭菌(Clostridium beijerinckii)ART124发酵生产丁醇的培养条件进行优化.首先利用Plackett - Burman试验设计筛选出影响丁醇生产的3个重要因素CaCO3和NH4 HCO3和K2HPO4的用量,再通过最陡爬坡路径逼近最大向应区域,最后根据响应面中心组合设计理论,确定主要影响因素的最佳条件:CaCO3、NH4HCO3和K2HPO4的质量浓度分别为2.65、2.16和0.43 g/L.利用数学模型分析预测得甘蔗糖蜜质量浓度为30 g/L时,最佳的丁醇产量为8.10 g/L,比优化前提高了53.14％.在最佳工艺条件下得到的实验结果与模型预测值很吻合,说明所建立的模型是有效的.     

Kinetics of amyl alcohol production during ethanol fermentation of blackstrap molasses

This paper reports results of studies on the effect of increasing amyl alcohol production on the kinetics and on the yield of ethanol fermentation with molasses as substrate. The production of amyl alcohols at concentrations of up to 1·0 g litre⁻¹ did not affect the alcoholic fermentation. The amyl alcohol yields, calculated as a percentage of the theoretical production, were 66· 4% from l-leucine,57·3% from l-isoleucine, 55·7% from a mixture of l-leucine and l-isoleucine, and 36·1% from racemic leucine. Aeration did not affect the yield of amyl alcohols. When no amino acid was added to the mash, the kinetics of amyl alcohol production as well as the final amyl alcohol concentration depended mainly on the inoculum size. When 2·0 g litre⁻¹ of l-leucine or of racemic leucine were added to the fermentation media, the initial stages of the kinetic patterns and the values of the maximum rate of amyl alcohol production were almost the same.     

Enhanced poly(L-malic acid) production from pretreated cane molasses by Aureobasidium pullulans in fed-batch fermentation

Poly(L-malic acid) (PMA) is a natural polyester with many attractive properties for biomedical application. However, the cost of PMA production is high when glucose is used as a carbon source. To solve this problem, cane molasses as a low-cost feedstock was applied for the production of PMA. Six pretreatment methods were applied to cane molasses before fermentation. Pretreatment with combined tricalcium phosphate, potassium ferrocyanide, and sulfuric acid (TPFSA) removed significant amounts of metal ions from cane molasses. The PMA concentration increased from 5.4?g/L (untreated molasses) to 36.9?g/L (TPFSA-pretreated molasses) after fermentation in shake flasks. A fed-batch fermentation strategy was then developed. In this method, TPFSA-pretreated cane molasses solution was continuously fed into the fermentor to maintain the total sugar concentration at 20?g/L. This technique generated approximately 95.4?g/L PMA with a productivity of 0.57?g/L/hr. The present study indicated that fed-batch fermentation using pretreated cane molasses is a feasible technique for producing high amounts of PMA.     

Economical succinic acid production from cane molasses by Actinobacillus succinogenes

In this work, production of succinic acid by Actinobacillus succinogenes CGMCC1593 using cane molasses as a low cost carbon source was developed. In anaerobic bottles fermentation, succinic acid concentration of 50.6+/-0.9 g l(-1) was attained at 60 h using an optimum medium containing molasses pretreated with sulfuric acid, resulting in a succinic acid yield of 79.5+/-1.1% and sugar utilization of 97.1+/-0.6%. When batch fermentation was carried out in a 5-l stirred bioreactor with pretreated molasses, 46.4 g l(-1) of succinic acid was attained at 48 h and faster cells growth was also observed. Fed batch fermentation was performed to minimize the substrate (sugar) inhibition effect, giving 55.2 g l(-1) of succinic acid and 1.15 g l(-1)h(-1) of productivity at 48 h. The present study suggests that the inexpensive cane molasses could be utilized for the economical and efficient production of succinic acid by A. succinogenes.