Ethanol production from mahula (Madhuca latifolia L.) flowers with immobilized cells of Saccharomyces cerevisiae in Luffa cylindrica L. sponge discs

The dried spongy fruit of luffa (Luffa cylindrica L.), a cucurbitaceous crop available in abundance in tropical and sub-tropical countries has been found to be a promising material for immobilizing microbial cells. The aim of the present study was to examine the ethanol production from mahula flowers in submerged fermentation using whole cells of Saccharomyces cerevisiae immobilized in luffa sponge discs. The cells not only survived but also were physiologically active in three more cycles of fermentation without significant reduction (<5%) in ethanol production. After 96 h, there was 91.1% sugar conversion producing 223.2 g ethanol/kg flowers (1st cycle) which was 0.99%, 2.3% and 3.2% more than 2nd (221 g ethanol/kg flowers), 3rd (218 g ethanol/kg flowers) and 4th (216 g ethanol/kg flowers) cycle of fermentation, respectively. Furthermore, ethanol production by immobilized cells was 8.96% higher than the free cells.     

Ethanol production from bread residues

Bread residues were converted into a suitable fermentation feed via a two-step starch hydrolysis using amylolytic enzymes. Wheat flour hydrolysis was also carried out at the same conditions for comparison. For the first stage, namely liquefaction, effects of temperature (50–85 °C) and substrate concentration (20% and 35%) were investigated. The 3-h liquefaction of the 20% bread suspension made 70% of initial dry matter soluble regardless of the temperature. The liquefaction of the 35% bread suspension had to be carried out by a fed-batch method due to the pasty behavior of the suspension. It resulted in a 65% dissolution of the suspended bread at 85 °C. Saccharification of the latter product led to a fermentation feedstock having a dextrose equivalent (DE) of more than 95 and almost 80% dissolution of the initial dry matter. The prepared feedstock was then cultivated using Saccharomyces cerevisiae, which resulted in an overall yield of 350 g ethanol per kg of initial bread dry matter. Staling of the bread for a week had no effect on liquefaction, saccharification and ethanol yield.     

Ethanol production from enzymatic hydrolysis of sugarcane bagasse pretreated with lime and alkaline hydrogen peroxide

In this work we evaluated ethanol production from enzymatic hydrolysis of sugarcane bagasse. Two pretreatments agents, lime and alkaline hydrogen peroxide, were compared in their performance to improve the susceptibility of bagasse to enzymatic action. Mild conditions of temperature, pressure and absence of acids were chosen to diminish costs and to avoid sugars degradation and consequent inhibitors formation. The bagasse was used as it comes from the sugar/ethanol industries, without grinding or sieving, and hydrolysis was performed with low enzymes loading (3.50 FPU g⁻¹ dry pretreated biomass of cellulase and 1.00 CBU g⁻¹ dry pretreated biomass of ??-glucosidase). The pretreatment with alkaline hydrogen peroxide led to the higher glucose yield: 691 mg g⁻¹ of glucose for pretreated bagasse after hydrolysis of bagasse pretreated for 1 h at 25 °C with 7.35% (v/v) of peroxide. Fermentation of the hydrolyzates from the two pretreatments were carried out and compared with fermentation of a glucose solution. Ethanol yields from the hydrolyzates were similar to that obtained by fermentation of the glucose solution. Although the preliminary results obtained in this work are promising for both pretreatments considered, reflecting their potential for application, further studies, considering higher biomass concentrations and economic aspects should be performed before extending the conclusions to an industrial process.     

Empty fruit bunches from oil palm as a potential raw material for fuel ethanol production

In this paper the fuel ethanol production from empty fruit bunches was experimentally evaluated using alkaline pretreatment and enzymatic hydrolysis for sugars release. Fermentation was accomplished using a native Saccharomyces cerevisiae strain. Ethanol concentration was carried on using a glass bench-scale distillation column. Experimental results were used for planning and designing the process scheme using Aspen Plus. Process simulation allowed calculating the mass and energy balances. It was found that coupling alkaline pretreatment with a later autoclaving improved the sugars yield in enzymatic hydrolysis. However, the use of the remaining soaking solution from pretreatment as hydrolysis medium had negative effects on sugars yield suggesting that there exist inhibit substance for the enzyme. Better results for enzymatic hydrolysis were obtained when sodium acetate buffer was used. Ethanol yield obtained from both experiments and simulation were very similar (66.50 and 65.84 dm³ of ethanol per each t of empty fruit bunches, respectively). These low ethanol yields were obtained because the native S. cerevisiae does not assimilate all reducing sugars, suggesting that those sugars were pentoses. Simulated alkaline and autoclaving pretreatment contributed only with 2% of the total energy consumption (198.4 GJ m⁻³ ethanol) while product recovery represented 57% of the total energy.     

Bioethanol production from sweet sorghum: Evaluation of post-harvest treatments on sugar extraction and fermentation

Three experimental sweet sorghum varieties (M81, Topper and Theis) and three post-harvest conditions were evaluated for ethanol production: juices extracted by milling were obtained from the whole plant, plant without panicle, and stalk (plant without panicle and leaves), respectively. A linear relationship was found between the total fermentable sugar concentrations and Brix degrees of the juices, which can predict the potential ethanol yield by field analytical tests. The juice extractability presented different behavior among the sweet sorghum varieties with respect to the treatments studied. However such treatments did not affect the level of sugar concentration of the juices obtained and the fermentation efficiency. Topper and Theis showed the best performance in terms of ethanol concentration, fermentation efficiency and ethanol yield. The variety used and its post-harvest treatment should be appropriately selected in order to improve the ethanol production from sweet sorghum.     

Comparative study of bio-ethanol production from mahula (Madhuca latifolia L.) flowers by Saccharomyces cerevisiae and Zymomonas mobilis

Mahula (Madhuca latifolia L.) flower is a suitable alternative cheaper carbohydrate source for production of bio-ethanol. Recent production of bio-ethanol by microbial fermentation as an alternative energy source has renewed research interest because of the increase in the fuel price. Saccharomyces cerevisiae (yeast) and Zymomonas mobilis (bacteria) are two most widely used microorganisms for ethanol production. In this study, experiments were carried out to compare the potential of the yeast S. cerevisiae (CTCRI strain) with the bacterium Z. mobilis (MTCC 92) for ethanol fermentation from mahula flowers. The ethanol production after 96 h fermentation was 149 and 122.9 g kg⁻¹ flowers using free cells of S. cerevisiae and Z. mobilis, respectively. The S. cerevisiae strain showed 21.2% more final ethanol production in comparison to Z. mobilis. Ethanol yield (Yx/s), volumetric product productivity (Qp), sugar to ethanol conversion rate (%) and microbial biomass concentration (X) obtained by S. cerevisiae were found to be 5.2%, 21.1%, 5.27% and 134% higher than Z. mobilis, respectively after 96 h of fermentation.     

Studies on ethanol production from water hyacinth—A review

With industrial development growing rapidly, there is a need for environmentally sustainable energy sources. Ethanol from biomass, bioethanol, is an attractive, sustainable energy fuel source for transportation. Based on the premise that fuel bioethanol can contribute to a cleaner environment and with the implementation of environmental protection laws in many countries, demand for this fuel is increasing. Efficient ethanol production is based on optimized processes where utilization of cheap substrates is highly demanding. Utilization of different types of lignocellulosic materials can be considered for production of ethanol. Among various types of lignocellulosic substances water hyacinth (Eichhornia crassipes) is a potential resource available in many tropical regions of the world. It is a noxious aquatic weed which grows fast. A considerable amount of research work is in progress for its bioconversion into ethanol using two-sequential steps of hydrolysis and fermentation. This paper reviews the bioconversion of water hyacinth to ethanol.     

Bioethanol production from mahula (Madhuca latifolia L.) flowers by solid-state fermentation

There is a growing interest worldwide to find out new and cheap carbohydrate sources for production of bioethanol. In this context, the production of ethanol from mahula (Madhuca latifolia L.) flowers by Saccharomyces cerevisiae in solid-state fermentation was investigated. The moisture level of 70%, pH of 6.0 and temperature of 30 °C were found optimum for maximum ethanol concentration (225.0 ± 4.0 g/kg flower) obtained from mahula flowers after 72 h of fermentation. Concomitant with highest ethanol concentration, the maximum ethanol productivity (3.13 g/kg flower/h), yeast biomass (18.5 × 10⁸ CFU/g flower), the ethanol yield (58.44 g/100 g sugar consumed) and the fermentation efficiency (77.1%) were also obtained at these parametric levels.     

利用厨余垃圾制备生物燃料乙醇的工艺技术

针对我国厨余垃圾的资源环境问题,本文对厨余垃圾转化为燃料乙醇过程,如厌氧发酵法、直接发酵法、分步糖化发酵技术、同步糖化发酵技术、联合生物加工以及固定化细胞技术等工艺技术路线进行了分析,并对利用餐厨垃圾制备生物燃料乙醇未来的发展前景进行了展望。     

Evaluation of an adapted inhibitor-tolerant yeast strain for ethanol production from combined hydrolysate of softwood

In order to evaluate the potential of an adapted inhibitor-tolerant yeast strain developed in our lab to produce ethanol from softwood, the effect of furfural and HMF presented in defined medium and pretreatment hydrolysate on cell growth was investigated. And the efficiency of ethanol production from enzymatic hydrolysate mixed with pretreatment hydrolysate of softwood by bisulfite and sulfuric acid pretreatment process was reported. The results showed that in the combined treatments of the two inhibitors, cell growth was not affected at 1 g/L each of furfural and HMF. When 3 g/L each of furfural and HMF was applied, the adapted strain responded with an extended lag phase of 24 h. Both in batch and fed-batch runs of combined hydrolysate fermentation, the final ethanol concentrations were above 20.0 g/L and the ethanol yields (Y_p/s) on the total amount of fermentable sugar presented in the pretreated materials were above 0.40 g/g. It implies the great promise of the yeast strain for improving ethanol production from softwood due to its high ability of metabolizing inhibitor compounds of furfural and HMF.     

Acidophilic biohydrogen production from rice slurry

Batch experiment results showed that hydrogen production from rice slurry was found most effective at pH 4.5, 37 °C treating a slurry containing 5.5 g-carbohydrate/L. An anaerobic digester sludge was used as seed after a 100 °C heat treatment for 30 min. After a 36 h acclimation period, the sludge had a maximum specific hydrogen production rate of 2.1 L/(g-VSS d) and a hydrogen yield of 346 mL/g-carbohydrate, corresponding to 62.6% of stoichiometric yield. The effluent was composed mostly of acetate (28.3–43.0%) and butyrate (51.4–70.9%). Based on the 16S rDNA analysis, the 28 clones developed from this acidophilic hydrogen-producing sludge may be classified into nine OTUs, all of which are affiliated with the genus Clostridium. Phylogenetic analysis shows that eight OTUs (96.4% of population) form a distinct group with Clostridium sp. 44a-T5zd. Results indicate the acidophilic hydrogen-producing bacteria found in this study are unknown, and warrant further studies.     

Bioethanol production from sweet potato by co-immobilization of saccharolytic molds and Saccharomyces cerevisiae

To investigate the bioethanol production from sweet potato, the saccharification and fermentation conditions of co-immobilization of saccharolytic molds (Aspergillus oryzae and Monascus purpureus) with Saccharomyces cerevisiae were analyzed. The immobilized yeast cells showed that at 10% glucose YPD (yeast extract peptone dextrose) the maximum fermentation rate was 80.23%. Viability of yeasts cells were 95.70% at a final ethanol concentration of 6%. Immobilization enhanced the ethanol tolerance of yeast cells. In co-immobilization of S. cerevisiae with A. oryzae or M. purpureus, the optimal hardening time of gel beads was between 15 and 60 min. Bioethanol production was 3.05-3.17% (v v⁻¹) and the Y_E/s (yield of ethanol production/starch consumption) was 0.31-0.37 at pH 4, 30 °C and 150 rpm during 13 days fermentation period. Co-immobilization of S. cerevisiae with a mixed cultures of A. oryzae and M. purpureus at a ratio of 2:1, the bioethanol production was 3.84% (v v⁻¹), and the Y_E/s was 0.39 for a 11 days incubation. However a ratio of A. oryzae and M. purpureus at 1:2 resulted a bioethanol production rate of 4.08% (v v⁻¹), and a Y_E/s of 0.41 after 9 days of fermentation.     

Production of bio-ethanol from an innovative mixture of surgical waste cotton and waste card board after ammonia pre-treatment

Ethanol production from waste biomass using a slightly modified bio-refinery approach was performed in this work to cater to the increasing need of alternate fuels and fuel additives globally. A surgical waste cotton and waste packaging cardboard mixture after a 15% v/v ammonia pre-treatment showed 70% lignin removal. An optimized saccharification using In-house Cellulases produced from Trichoderma harzanium ATCC 20846 had a percentage saccharification of 45% and percentage yield saccharification of 94.6%. An optimized fermentation using Saccharomyces cereviseae strain RW143 resulted in the yield of 0.4 g ethanol/g glucose from the 15% (v/v) glucose in the enzymatically saccharified hydrolysate loaded. The distilled ethanol had 90% (v/v) concentration and180 proof (twice the amount of concentration percentage in v/v) purity. 1 kg biomass mixture when processed as mentioned would yield 120 mL ethanol. Two diesel-ethanol blends (E-10 and E-20) and a commercial Diesel control were used to rate an IC engine’s brake power.     

Studying the ability of Fusarium oxysporum and recombinant Saccharomyces cerevisiae to efficiently cooperate in decomposition and ethanolic fermentation of wheat straw

Fusarium oxysporum F3 alone or in mixed culture with Saccharomyces cerevisiae F12 were used to ferment carbohydrates of wet exploded pre-treated wheat straw (PWS) directly to ethanol. Both microorganisms were first grown aerobically to produce cell mass and thereafter fermented PWS to ethanol under anaerobic conditions. During fermentation, soluble and insoluble carbohydrates were hydrolysed by the lignocellulolytic system of F. oxysporum. Mixed substrate fermentation using PWS and corn cobs (CC) in the ratio 1:2 was used to obtain an enzyme mixture with high cellulolytic and hemicellulolytic activities. Under these conditions, activities as high as 34300, 9100, 326, 24, 169, 27 and 254 U dm⁻³ of xylanase, endoglucanase, ??-glucosidase, arabinofuranosidase, avicelase, feruloyl esterase and acetyl esterase, respectively, were obtained. The replacement of the enzyme production phase of F. oxysporum by the addition of commercially available enzymes Celluclast^® 1.5 L FG and Novozym^® 188 in 3:1 ratio for the treatment of PWS, resulted in a 3-fold increase in the volumetric ethanol productivity without increasing the ethanol production significantly. By direct bioconversion of 110 kg m⁻³ dry matter of PWS, ethanol concentration (4.9 kg m⁻³) and yield (40 g kg⁻¹ of PWS) were similarly obtained by F. oxysporum and the mixed culture, while productivity rates as high as 34 g m⁻³ h⁻¹ and 108 g m⁻³ h⁻¹ were obtained by F. oxysporum and the mixed culture, respectively.     

Optimal fermentation conditions for maximizing the ethanol production by Kluyveromyces fragilis from cheese whey powder

Cheese whey powder (CWP) is an attractive raw material for ethanol production since it is a dried and concentrated form of CW and contains lactose in addition to nitrogen, phosphate and other essential nutrients. In the present work, deproteinized CWP was utilized as fermentation medium for ethanol production by Kluyveromyces fragilis. The individual and combined effects of initial lactose concentration (50-150 kg m⁻³), temperature (25-35 °C) and inoculum concentration (1-3 kg m⁻³) were investigated through a 2³ full-factorial central composite design, and the optimal conditions for maximizing the ethanol production were determined. According to the statistical analysis, in the studied range of values, only the initial lactose concentration had a significant effect on ethanol production, resulting in higher product formation as the initial substrate concentration was increased. Assays with initial lactose concentration varying from 150 to 250 kg m⁻³ were thus performed and revealed that the use of 200 kg m⁻³ initial lactose concentration, inoculum concentration of 1 kg m⁻³ and temperature of 35 °C were the best conditions for maximizing the ethanol production from CWP solution. Under these conditions, 80.95 kg m⁻³ of ethanol was obtained after 44 h of fermentation.     

Selection of yeast strains for alcoholic fermentation of sugar beet thick juice and green syrup

Presented work aimed at determination of effect of various strains of yeast Saccharomyces cerevisiae and concentration of fermentation worts on dynamics and efficiency of alcoholic fermentation. Fermentation worts contained either thick juice or green syrup.It was found that yeast strains designated as M₁, M₂ and D-2 most efficiently fermented thick juice worts inoculated with yeast cream at a rate of 2 kg m⁻³ of wort. Fermentation processes lasted for approximately 2 days and ethanol yield approached 92-94% of the theoretical yield. Fermentations of green syrup worts were most efficient (ethanol yield reached 90-92% of the theoretical yield) when these processes were carried out by yeast strains M₁, M₂, D-2 and As4 (inoculum - 2 kg m⁻³ of wort).S. cerevisiae strains M₁ and M₂ dynamically and efficiently fermented thick juice worts with extract of 200 g kg⁻¹ and 250 g kg⁻¹ (89-94% of the theoretical yield) while strain D-2 preferred less dense worts (extract of 200 g kg⁻¹) and produced ethanol with the yield of over 92% of the theoretical yield. The optimum green syrup worts extract was 200 g kg⁻¹.     

Fermentative hydrogen production from macro-algae Laminaria japonica using anaerobic mixed bacteria

In this study, one macro-alga (Laminaria japonica) was used for fermentative hydrogen production by anaerobic mixed bacteria. The saccharification efficiency and hydrogen production by L. japonica with four different pretreatment methods, including heat, acid, alkaline and ultrasonic treatment, were investigated. The results showed that the saccharification efficiency from L. japonica that was pretreated with acid was the highest among the four methods. The saccharification efficiency for the total reducing sugars in the acid-pretreated L. japonica was 350.54 ± 19.89 mg/g (mean ± S.E.). The cumulative hydrogen production was 66.68 ± 5.68 mL/g from the heat-pretreated L. japonica, whereas that of L. japonica that was subjected to acid, alkaline, and ultrasonic pretreatment and the control was 43.65 ± 6.87 mL/g, 15.00 ± 3.89 mL/g, 23.56 ± 4.56 mL/g and 10.00 ± 1.21 mL/g, respectively. In addition, the effects of substrate concentration and initial pH on hydrogen production from heat-pretreated L. japonica were also analyzed. The results showed that the maximum hydrogen production was 83.45 ± 6.96 mL/g with a hydrogen concentration of approximately 28.4% from heat-pretreated L. japonica when the initial pH and substrate concentration were determined to be 6.0 and 2%, respectively. Heat pretreatment was the most effective method for increasing fermentative hydrogen production when L. japonica was used as the only substrate.     

Conversion of paper sludge to ethanol by separate hydrolysis and fermentation (SHF) using Saccharomyces cerevisiae

The conversion of ethanol from paper sludge using the separate hydrolysis and fermentation (SHF) process with cellulase and Saccharomyces cerevisiae GIM-2 were investigated in this paper. Optimization strategy based on statistical experimental designs was employed to enhance degree of saccharification by enzymatic hydrolysis of paper sludge. Based on the Plackett-Burman design, hydrolysis time, substrate concentration and cellulase dosage were selected as the most significant variable on the degree of saccharification. Subsequently, the optimum combination of the selected factors was investigated by a Box-Behnken approach. A mathematical model was developed to show the effects of each factor and their combinatorial interactions on the degree of saccharification. The optimal conditions were hydrolysis time 82.7 h, substrate concentration 40.8 g L⁻¹ and cellulase dosage 18.1 FPU g⁻¹ substrate, and a degree of saccharification of 82.1% can be achieved. When hydrolysate was further fermented with S. cerevisiae GIM-2, the conversion rate of sugar to ethanol was 34.2% and the ethanol yield was 190 g kg⁻¹ of dry paper sludge, corresponding to an overall conversion yield of 56.3% of the available carbohydrates on the initial substrate. The results derived from this study indicate that the response surface methodology is a useful tool for optimizing the hydrolysis conditions to converse paper sludge to ethanol.     

Ethanol production process from banana fruit and its lignocellulosic residues: Energy analysis

Tropical countries, such as Brazil and Colombia, have the possibility of using agricultural lands for growing biomass to produce bio-fuels such as biodiesel and ethanol. This study applies an energy analysis to the production process of anhydrous ethanol obtained from the hydrolysis of starch and cellulosic and hemicellulosic material present in the banana fruit and its residual biomass. Four different production routes were analyzed: acid hydrolysis of amylaceous material (banana pulp and banana fruit) and enzymatic hydrolysis of lignocellulosic material (flower stalk and banana skin). The analysis considered banana plant cultivation, feedstock transport, hydrolysis, fermentation, distillation, dehydration, residue treatment and utility plant. The best indexes were obtained for amylaceous material for which mass performance varied from 346.5 L/t to 388.7 L/t, Net Energy Value (NEV) ranged from 9.86 MJ/L to 9.94 MJ/L and the energy ratio was 1.9 MJ/MJ. For lignocellulosic materials, the figures were less favorable; mass performance varied from 86.1 to 123.5 L/t, NEV from 5.24 to 8.79 MJ/L and energy ratio from 1.3 to 1.6 MJ/MJ. The analysis showed, however, that both processes can be considered energetically feasible.