Concentration Of Fermentable Sugars Research Articles

Microwave assisted hydrothermal as greener pretreatment of brewer’s spent grains for biobutanol production

A microwave assisted hydrothermal pretreatment technology has been developed to recover fermentable sugars from brewer’s spent grain. Microwave hydrothermal pretreatment is considered as a greener pretreatment, as no acid or alkali are used as catalysts. An experimental design was planned to analyze the effect of pretreatment conditions (temperature and time). The objective was to maximize hemicellulosic sugar recovery in the liquid fraction and glucose recovery in enzymatic hydrolysis (referred to untreated BSG), as well as to minimize inhibitors in the liquid fraction to ensure ABE (acetone, butanol and ethanol) fermentability. Optimal conditions were 192.7 °C and 5.4 min, resulting in 64% hemicellulosic sugar recovery, 70% glucose recovery in enzymatic hydrolysate and 2.4 g/L total inhibitors. The liquid fraction obtained under optimal conditions was fermented with Clostridium beijerinckii, reaching a butanol concentration as low as 1 g/L. The butanol concentration could be improved by operating at higher solid loadings in pretreatment, which would increase fermentable sugar concentration. Enzymatic hydrolysis of pretreated BSG yielded a sugar solution, which was also fermented, resulting in a butanol concentration and overall yield of 8.3 g/L and 46 kg/t BSG, respectively.

Engineering Saccharomyces cerevisiae for co-utilization of d-galacturonic acid and d-glucose from citrus peel waste

Pectin-rich biomasses, such as citrus peel and sugar beet pulp, hold promise as inexpensive feedstocks for microbial fermentations as enzymatic hydrolysis of their component polysaccharides can be accomplished inexpensively to yield high concentrations of fermentable sugars and d-galacturonic acid (d-galUA). In this study, we tackle a number of challenges associated with engineering a microbial strain to convert pectin-rich hydrolysates into commodity and specialty chemicals. First, we engineer d-galUA utilization into yeast, Saccharomyces cerevisiae. Second, we identify that the mechanism of d-galUA uptake into yeast is mediated by hexose transporters and that consumption of d-galUA is inhibited by d-glucose. Third, we enable co-utilization of d-galUA and d-glucose by identifying and expressing a heterologous transporter, GatA, from Aspergillus niger. Last, we demonstrate the use of this transporter for production of the platform chemical, meso-galactaric acid, directly from industrial Navel orange peel waste.

Molecular brewing: Molecular structural effects involved in barley malting and mashing

Ten barley samples containing varied protein contents were subject to malting followed by mashing to investigate molecular effects of both barley starch and starch- protein interactions on malting and mashing performances, and the underlying mechanism. Starch granular changes were examined using differential scanning calorimetry and scanning electron microscopy. The molecular fine structures of amylose and amylopectin from unmalted and malted grain were obtained using size-exclusion chromatography. The results showed that both amylose and amylopectin polymers were hydrolyzed at the same time during malting. Protein and amylose content in both unmalted and malted barley significant negatively correlated with fermentable sugar content after mashing. While protein content is currently the main criterion for choosing malting varieties, this study shows that information about starch molecular structure is also useful for determining the release of fermentable sugars, an important functional property. This provides brewers with some new methods to choose malting barley.

Saccharomyces cerevisiae Exponential Growth Kinetics in Batch Culture to Analyze Respiratory and Fermentative Metabolism.

Saccharomyces cerevisiae cells in the exponential phase sustain their growth by producing ATP through fermentation and/or mitochondrial respiration. The fermentable carbon concentration mainly governs how the yeast cells generate ATP; thus, the variation in fermentable carbohydrate levels drives the energetic metabolism of S. cerevisiae. This paper describes a high-throughput method based on exponential yeast growth to estimate the effects of concentration changes and nature of the carbon source on respiratory and fermentative metabolism. The growth of S. cerevisiae is measured in a microplate or shaken conical flask by determining the optical density (OD) at 600 nm. Then, a growth curve is built by plotting OD versus time, which allows identification and selection of the exponential phase, and is fitted with the exponential growth equation to obtain kinetic parameters. Low specific growth rates with higher doubling times generally represent a respiratory growth. Conversely, higher specific growth rates with lower doubling times indicate fermentative growth. Threshold values of doubling time and specific growth rate are estimated using well-known respiratory or fermentative conditions, such as non-fermentable carbon sources or higher concentrations of fermentable sugars. This is obtained for each specific strain. Finally, the calculated kinetic parameters are compared with the threshold values to establish whether the yeast shows fermentative and/or respiratory growth. The advantage of this method is its relative simplicity for understanding the effects of a substance/compound on fermentative or respiratory metabolism. It is important to highlight that growth is an intricate and complex biological process; therefore, preliminary data from this method must be corroborated by the quantification of oxygen consumption and accumulation of fermentation byproducts. Thereby, this technique can be used as a preliminary screening of compounds/substances that may disturb or enhance fermentative or respiratory metabolism.

Operation performance of up-flow anaerobic sludge blanket (UASB) bioreactor for biohydrogen production by self-granulated sludge using pre-treated palm oil mill effluent (POME) as carbon source

Palm oil mill effluent (POME), an agro-industrial wastewater with high solids content, was subject to hydrolysis by 1% (w/v) nitric acid in order to increase its solubility and the fermentable sugar content from its cellulosic component. POME hydrolysate was then evaluated in an up-flow anaerobic sludge blanket (UASB) bioreactor for the production of biohydrogen gas via mixed culture under thermophilic conditions. The bioreactor was fed with pre-treated POME under varied hydraulic retention time (HRT) between 48 and 3 h at constant cycle length of 24 h to test the productivity of H2 and the stability of UASB; no washout of biomass occurred at any cycle and the system managed to recover its H2 production rate (HPR) after initial fluctuations. In this study, H2-producing granules (HPGs) were formed shortly after the start-up period, and were analysed by FESEM, FTIR, SEM-EDX, and their extracellular polymeric substances (EPS) content. The maximum HY and HPR achieved were 2.45 mol-H2/mol-sugar and 11.75 LH2/LPOME d−1, respectively, at HRT 6 h. Acetic acid was found to be the major by-product at all HRTs, followed by butyric acid, while Clostridium spp. was found to be the most dominant H2-producing bacteria in the system. Results suggest that UASB has a good potential for stable H2 production with high POME digestion rate.

RETRACTED: Boosting the fermentable sugar yield and concentration of corn stover by magnesium oxide pretreatment for ethanol production

MgO pretreatment was investigated to boost the fermentable sugars derived from corn stover with LHW pretreatment as control. Compared to LHW pretreatment, MgO pretreatment caused twice hemicellulose recovery (42 vs 21%). Double hemicellulose recovery not only didn't affect glucose yield but increased xylose yield by 13% and total sugar yield by 6% under the optimal conditions (pretreatment: 10% biomass loading, 0.1 mol/L MgO, 190 °C, and 40 min; hydrolysis: pretreated biomass loading of 10 g/100 mL, enzyme loading of 1 mL/g pretreated biomass, 50 °C, and 120 h). A total sugar concentration of 50 g/L was obtained under the above conditions. Besides, the enzyme component hydrolyzing xylan may be prone to deactivation by lignin residues in pretreated biomass. Both SEM and FTIR analyses indicate that MgO effectively disrupted the biomass structures and enlarged the exposed surface area of carbohydrates, thus boosting the enzymatic hydrolysis and fermentable sugars for ethanol production.

Optimization of dilute acid pretreatment of barley husk and oat husk and determination of their chemical composition

The pretreatment of renewable resources is the first step to make them metabolically available for microorganisms for generation of value-added products by fermentation. In this research, barley husk (BH) and oat husk (OH) were used as renewable resources to study the optimization of dilute acid pretreatment conditions by using Response Surface Methodology (RSM). Temperature (T, 110–130 °C), solid-to-liquid ratio (S:L, 1:8–1:16 w/v), dilute sulfuric acid concentration (DSA, 1–5%, v/v), and pretreatment time (t, 30–90 min) were selected as independent variables. Their levels were specified by one-factor-at-a-time (OFAT) method according to statistically significance level (p = 0.05). OFAT results indicated that the independent variables for optimization of acid pretreatment conditions of the renewable resources were T (120–130 °C), S:L (1:8–1:12 w/v), and DSA (1–3% v/v) for BH; T (120–130 °C), S:L (1:8–1:12 w/v), and t (10–30 min) for OH. Optimum pretreatment values were 130 °C, 1:8 (w/v), 1.86% (v/v), and 30 min for BH and 130 °C, 1:8 (w/v), 1% (v/v), and 19 min for OH by using Box-Behnken RSM. Under optimal conditions, fermentable sugar concentration, total phenolics, and extract yield were determined to be 76.28, 1.12 g/L, and 55% for BH and 59.63 g/L, 0.70 g/L, and 56% for OH, respectively. Additionally, the chemical composition of hydrolysates was also evaluated in terms of maltose, glucose, xylose, arabinose, mannose, galactose, phenolics, 5-hydroxymthylfurfural, 2-furaldehyde (2-F), formic acid, and acetic acid. Catalytic efficiency values of sulfuric acid for BH and OH were 21.58 and 8.35 g/g, respectively. Consequently, this study clearly indicates that the hydrolysates from the renewable resources can be used as feedstocks for the production of value-added products by biotechnological processes.

Use of agro-industrial residue from the canned pineapple industry for polyhydroxybutyrate production by Cupriavidus necator strain A-04

BackgroundPineapple is the third most important tropical fruit produced worldwide, and approximately 24.8 million tons of this fruit are produced annually throughout the world, including in Thailand, which is the fourth largest pineapple producer in the world. Pineapple wastes (peel and core) are generated in a large amount equal to approximately 59.36% based on raw material. In general, the anaerobic digestion of pineapple wastes is associated with a high biochemical oxygen demand and high chemical oxygen demand, and this process generates methane and can cause greenhouse gas emissions if good waste management practices are not enforced. This study aims to fill the research gap by examining the feasibility of pineapple wastes for promoting the high-value-added production of biodegradable polyhydroxybutyrate (PHB) from the available domestic raw materials. The objective of this study was to use agro-industrial residue from the canned pineapple industry for biodegradable PHB production.ResultsThe results indicated that pretreatment with an alkaline reagent is not necessary. Pineapple core was sized to − 20/+ 40 mesh particle and then hydrolyzed with 1.5% (v/v) H2SO4 produced the highest concentration of fermentable sugars, equal to 0.81 g/g dry pineapple core, whereas pineapple core with a + 20 mesh particle size and hydrolyzed with 1.5% (v/v) H3PO4 yielded the highest concentration of PHB substrates (57.2 ± 1.0 g/L). The production of PHB from core hydrolysate totaled 35.6 ± 0.1% (w/w) PHB content and 5.88 ± 0.25 g/L cell dry weight. The use of crude aqueous extract (CAE) of pineapple waste products (peel and core) as a culture medium was investigated. CAE showed very promising results, producing the highest PHB content of 60.00 ± 0.5% (w/w), a cell dry weight of 13.6 ± 0.2 g/L, a yield (Y_{{{P mathord{left/ {vphantom {P S}} right. kern-0pt} S}}}) of 0.45 g PHB/g PHB substrate, and a productivity of 0.160 g/(L h).ConclusionsThis study demonstrated the feasibility of utilizing pineapple waste products from the canned pineapple industry as lignocellulosic feedstocks for PHB production. C. necator strain A-04 was able to grow on various sugars and tolerate levulinic acid and 5-hydroxymethyl furfural, and a detoxification step was not required prior to the conversion of cellulose hydrolysate to PHB. In addition to acid hydrolysis, CAE was identified as a potential carbon source and offers a novel method for the low-cost production of PHB from a realistic lignocellulosic biomass feedstock.

Dry weight and nutrient uptake of twenty one sweet sorghum genotypes grown in two separate locations of Turkey

Sweet sorghum (Sorghum bicolor L.) is a type of cultivated sorghums and has been recognized widely as potential alternative source of bio-fuel because of its high fermentable sugar content in the stalk. A substantial variation of dry matter (DM) yield and nutrient uptake information is needed for sweet sorghum genotypes under different climatic and soil conditions. The objectives of this study were (i) to assess the genotypic variation irrespective to dry matter yield and nutrient up take of sweet sorghum genotypes (ii) to investigate nitrogen use efficiency of sweet sorghum genotypes. This field study was conducted in Adana and Urfa location of Turkey for one growing season where twenty one sweet sorghum genotypes were used as testing plant that collected from USA. These twenty one genotypes were selected through screening of forty nine genotypes. The experiment was conducted randomized block design with four replications in both locations. Growth parameters, nutrient up take and nitrogen (N) use efficiency was determined for the twenty one sweet sorghum genotypes. Biomass yield exhibited non-significant differences among genotypes. In contrast, significant differences were observed between Adana and Urfa irrespective to biomass yield. The N use efficiency by several sweet genotypes varies from 385 to 836 kg/ha and 282 to 779 kg/ha in Adana and Urfa locations respectively. Sweet sorghum genotypes responded differently to potassium (K), calcium (Ca) and magnesium (Mg) uptake. The K uptake varies 381 to 1472 and 374 to 1405 kg/ha in Adana and Urfa locations respectively. The Ca uptake also varies 115 to 582 and 115 to 424 kg/ha in Adana and Urfa locations respectively. The Mg uptake varies 81 to 300 and 50 to 226 kg/ha in Adana and Urfa locations respectively. Our results suggest that diverse genotypic variation from different geographical regions should be considered from better sweet sorghum production from the collected sweet sorghum varieties. This study concluded that sweet sorghum genotypes may be used to develop new varieties with higher dry matter production and lower nutrient utilization by these genotypes along with the adaptations of several climatic conditions in Turkey.

Temperature Compensation on Sugar Content Prediction of Molasses by Near-Infrared Spectroscopy (NIR)

The rapid, nondestructive, cost-effective NIR measurement method was used for final molasses quality monitoring to determine fermentable sugar content to optimize ethanol yield. Molasses is stored in temperature-controlled tanks during the cane crushing and remelt seasons to ensure molasses quality and availability. However, there is variation in molasses temperature during storage. The impacts of temperature variation on molasses NIR spectra and calibration performance were studied. About one hundred molasses samples were collected for spectral profiling (400–2500 nm) at three different temperatures (25, 35 and 45 °C) using a FOSS NIR DS2500 spectrometer. A partial least squares regression (PLSR) model was developed using full cross-validation. The predictive models were developed using molasses spectra at 25, 35 and 45 °C and used to determine sucrose, glucose, fructose (fermentable sugars) concentrations in the molasses. External validation was achieved using thirty percent of calibration samples for each validation set, 25, 35, and 45 °C. Variation of the sample spectra was observed for the visible region and NIR region (1450 and 1970 nm), due to O–H bonding. The root means squared standard error of cross-validation obtained varied depending on sample temperature. Root means squared standard error of prediction results for external validation samples tended to increase with increasing temperature. Predicted values were not statistically different (p > 0.05) to reference values using different temperatures of models and validation. Calibration models including three temperature spectra showed potential of fermentable sugar analysis in molasses without temperature compensation.

Bioethanol production from rice straw by simultaneous saccharification and fermentation with statistical optimized cellulase cocktail and fermenting fungus

BackgroundRice straw is one of the abundant lignocellulosic biomass with potential as a feedstock for bioethanol production. To produce ethanol from the biomass biologically, enzymatic hydrolysis is necessary that can effectively degrade rice straw into fermentable sugars such as glucose and xylose. Many researches utilized many kinds of commercial cellulase reagents on the hydrolysis of cellulose. Since these have different enzyme activities, enzyme reagents suitable for each biomass must be selected. In this study, three appropriate cellulase reagents were selected by multivariate analysis technique and then optimized by design of experiments method for efficient hydrolysis of alkali-pretreated rice straw. Moreover, an ethanol production from the treated straw was performed by simultaneous saccharification and fermentation (SSF) with the optimized enzyme cocktail and xylose-fermenting fungus of Mucor circinelloides.ResultsPretreatment by alkali solution of rice straw resulted in the increase of fermentable sugar content from 56.3 to 80.0%. The desirable commercial enzyme reagents for saccharification of the straw were determined as a combination of “Cellulase Onozuka 3S”, “Cellulase T Amano 4”, and “Pectinase G Amano” by a multivariate analysis based on various cellulolytic activities of each reagent. The optimum mixing ratio was calculated by response surface method based on design of experiment method. The optimized cocktail successfully achieved 75.3 g/L in production of the total fermentable sugar by hydrolysis of alkali-treated rice straw that agreed with the hydrolysis efficiency of 94.1%. SSF of 100 g/L treated rice straw with the optimal cocktail and M. circinelloides under aerobic condition resulted in 30.5 g/L ethanol concentration for 36 h.ConclusionThe construction of cellulase cocktail by the proposed statistical method enabled efficient hydrolysis of alkali-treated rice straw. SSF process combining the optimized cocktail and a xylose-fermenting fungus could be expected as a promising system for ethanol production from various lignocellulosic biomasses.

Analysis of the oligosaccharide composition in wort samples by capillary electrophoresis with laser induced fluorescence detection

Determination of the oligosaccharide composition in different wort samples is important to monitor their change during the brewing process with different yeast types. In our work, the concentration of fermentable and non-fermentable sugars were monitored by capillary electrophoresis to observe the effect of two different types of yeasts, Saccharomyces pastorianus and Saccharomycodes ludwigii. The former first ferments the monosaccharides, then the higher sugar oligomers, such as maltose and maltotriose, to ethanol, while the latter fully ferments the monosaccharides, but ferments only very low percentages of the oligosaccharides. Therefore, breweries use Saccharomycodes ludwigii to produce beers with low alcohol content. The CE-LIF traces of the wort samples represented unique oligosaccharide signatures.

Optimization of thermal acid hydrolysis for bioethanol production from Ulva rigida with yeast Pachysolen tannophilus

We investigated the feasibility of bioethanol production from hydrolysate of green seaweed Ulva rigida. The pretreatment of the green macroalgae was optimized using thermal acid hydrolysis to obtain a high reducing sugars yield. The dry seaweed biomass, (5 to 15% w/v) was hydrolyzed with two different acid catalysts, H2SO4 and HCl at a concentration of 0 to 10.0% (v/v). The hydrolysis times ranging from 30 to 60min were investigated when the mixture was autoclaved. A condition of 4% (v/v) sulfuric acid, 10% (w/v) biomass loading and 1h of incubation time was optimum to obtain maximum total fermentable reducing sugar concentration of 34±0.25mg/ml and 0.50±0.02mg/ml of phenolic compounds. Fermentation of the hydrolysate using adapted and non-adapted Pachysolen tannophilus produced 0.12g/g and 0.09g/g (ethanol to dry seaweed), respectively. These preliminaries results indicate a potential use of the macroalgae U. rigida for bioethanol production.

Enhanced enzymatic saccharification of sugarcane bagasse pretreated by sodium methoxide with glycerol

Sodium methoxide (CH3ONa) with glycerol pretreatment (CWGP) was performed to improve the enzymatic digestibility of sugarcane bagasse (SCB). Response surface methodology was utilized to optimize the CWGP parameters for pretreating SCB from the perspective of total fermentable sugar yield (TFSY) and total fermentable sugar concentration (TFSC). Under the optimal CWGP conditions, 0.5666g/g of TFSY (0.82% CH3ONa, 1.11h, 150°C) and 17.75g/L of TFSC (0.87% CH3ONa, 1.38h, 149.27°C) were achieved, corresponding to delignification of 79.05% and 79.34%, respectively. Compared the pretreatment using glycerol or CH3ONa alone, the CWGP has significant synergies to enhance the enzymatic efficiency of SCB. The physical and chemical characteristics of untreated and pretreated SCBs were analyzed using FT-IR, XRD, and SEM, and the results suggest that CWGP significantly increased the susceptibility of the substrates to enzymatic digestibility. Ultimately, CWGP might be a prospective candidate for the pretreatment process of enzyme-based lignocellulosic biorefineries.

Microwave-assisted dilute acid pretreatment of different agricultural bioresources for fermentable sugar production

Microwave-assisted pretreatment can be used for fermentable sugar production from lignocellulosic biomass. In this study, the optimum hydrolysis conditions of barley husk, oat husk, wheat bran, and rye bran were determined in power level, treatment time, solid-to-liquid ratio and dilute acid ratio as follows: 700 W, 6.92 min, 1:18.26 w/v, and 3.67% for barley husk, 600 W, 6.96 min, 1:17.22 w/v, and 3.47% for oat husk, 600 W, 6.92 min, 1:16.69 w/v, and 1.85% for wheat bran, and 460 W, 6.15 min, 1:17.14 w/v, and 2.72% for rye bran. The fermentable sugar concentrations were 37.21 (0.68 g/g), 38.84 (0.67 g/g), 49.65 (0.83 g/g), and 36.27 g/L (0.62 g/g) under optimum conditions, respectively. The results showed that microwave-assisted pretreatment is a promising technology which can be successfully implemented for the hydrolysis of lignocellulosic biomass for high sugar yield. On the other hand, hydrolysates included some inhibitors such as organic acids, furans, and phenolic compounds. Lignocellulosic biomass used in this study can be employed as good feedstocks for value-added product production in the fermentation process, after the inhibitors have been detoxified/removed with different detoxification methods.

Otimização de parâmetros operacionais do pré-tratamento da palha de cana-de-açúcar

O compromisso de atender as necessidades do presente sem comprometer a possibilidade de suprir as necessidades das gerações futuras, torna a diversificação da matriz energética brasileira e mundial fator cada vez mais compulsório. Diante disso, o uso de biomassas lignocelulósicas para obtenção de combustíveis mais limpos do ponto de vista ambiental é amplamente discutido na atualidade. O etanol combustível pode ser obtido a partir de fontes alternativas de energia, como as biomassas lignocelulósicas. Esse tipo de matéria-prima possui elevado teor de açúcares fermentescíveis em sua composição. Porém, esses não se encontram diretamente disponíveis, sendo necessárias etapas adicionais para sua obtenção. Este trabalho teve como objetivo a otimização da etapa de pré-tratamento da palha de cana-de-açúcar, por meio de um delineamento experimental 22 com três repetições no ponto central. As variáveis de estudo foram: a razão palha/água (m/v) na etapa de pré-tratamento hidrotérmico e a temperatura reacional do pré-tratamento alcalino sequencial ao hidrotérmico. O estudo mostrou que a deslignificação não promoveu melhora significativa na conversão da celulose em glicose na hidrólise enzimática, o que não justifica a realização dessa etapa adicional, nas condições avaliadas. Já o pré-tratamento hidrotérmico apresentou bons resultados, alcançando na etapa de hidrólise conversões superiores a 85%, em especial para as razões palha/água 1:6,7 e 1:20 (m/v).

Near infrared spectroscopy determination of sucrose, glucose and fructose in sweet sorghum juice

Sweet sorghum is a very robust crop which has the potential to be used in ethanol production due to its high fermentable sugar content present in its stem juice, very similar to sugarcane. Therefore, for breeding purposes it is relevant to analyze sugar composition in the juice to characterize sweet sorghum genotypes and their period of industrial utilization within different environments for maximum ethanol yield. In this work we developed a rapid, low cost and efficient method to determine the profile of sugars (sucrose, glucose and fructose) in sorghum juice by near infrared spectroscopy and partial least square regression, and validation of the method was performed according to the high-performance liquid chromatography method. Developed models provided root mean square error of prediction of 4, 1 and 0.6mg·mL−1 and ratio performance deviations of 8, 5 and 5 for sucrose, glucose and fructose, respectively. Relative standard deviations of three sweet sorghum juice samples were reported with content variation (low, medium and high) 0.2, 0.3, 0.8% for sucrose; 1, 2, 2% for glucose; 1, 2, 3% for fructose. Sugar profile is an asset for crop breeders to take decisions for the development of more productive cultivars and higher sugar content.

Treatment of supermarket vegetable wastes to be used as alternative substrates in bioprocesses

Fruits and vegetables have the highest wastage rates at retail and consumer levels. These wastes have promising potential for being used as substrates in bioprocesses. However, an effective hydrolysis of carbohydrates that form these residues has to be developed before the biotransformation.In this work, vegetable wastes from supermarket (tomatoes, green peppers and potatoes) have been separately treated by acid, thermal and enzymatic hydrolysis processes in order to maximise the concentration of fermentable sugars in the final broth.For all substrates, thermal and enzymatic processes have shown to be the most effective. A new combined hydrolysis procedure including these both treatments was also assayed and the enzymatic step was successfully modelled. With this combined hydrolysis, the percentage of reducing sugars extracted was increased, in comparison with the amount extracted from non-hydrolysed samples, approximately by 30% in the case of tomato and green peeper wastes. For potato wastes this percentage increased from values lower than 1% to 77%. In addition, very low values of fermentation inhibitors were found in the final broth.

Over production of fermentable sugar for bioethanol production from carbohydrate-rich Malaysian food waste via sequential acid-enzymatic hydrolysis pretreatment

In Malaysia, the amount of food waste produced is estimated at approximately 70% of total municipal solid waste generated and characterised by high amount of carbohydrate polymers such as starch, cellulose, and sugars. Considering the beneficial organic fraction contained, its utilization as an alternative substrate specifically for bioethanol production has receiving more attention. However, the sustainable production of bioethanol from food waste is linked to the efficient pretreatment needed for higher production of fermentable sugar prior to fermentation. In this work, a modified sequential acid-enzymatic hydrolysis process has been developed to produce high concentration of fermentable sugars; glucose, sucrose, fructose and maltose. The process started with hydrothermal and dilute acid pretreatment by hydrochloric acid (HCl) and sulphuric acid (H2SO4) which aim to degrade larger molecules of polysaccharide before accessible for further steps of enzymatic hydrolysis by glucoamylase. A kinetic model is proposed to perform an optimal hydrolysis for obtaining high fermentable sugars. The results suggested that a significant increase in fermentable sugar production (2.04-folds) with conversion efficiency of 86.8% was observed via sequential acid-enzymatic pretreatment as compared to dilute acid pretreatment (∼42.4% conversion efficiency). The bioethanol production by Saccharomyces cerevisiae utilizing fermentable sugar obtained shows ethanol yield of 0.42g/g with conversion efficiency of 85.38% based on the theoretical yield was achieved. The finding indicates that food waste can be considered as a promising substrate for bioethanol production.

Vacuum-assisted alkaline pretreatment as an innovative approach for enhancing fermentable sugar yield and decreasing inhibitor production of sugarcane bagasse

Sodium hydroxide pretreatment of sugarcane bagasse under vacuum conditions was established and evaluated in this study. Compared to pretreatment under conventional moderate pressure conditions, only half of the total phenolic compounds and less than half of the formic acid were produced under vacuum conditions, while the yield of total fermentable sugar was significantly increased by 31.38%. The pretreatment parameters: NaOH concentration, pretreatment time, and pretreatment temperature, were optimized using response surface methodology based on the response values of the total fermentable sugar yield (TFSY) and the total fermentable sugar concentration (TFSC), respectively. Under the optimal conditions, the TFSY of 0.5146g/g and the TFSC of 17.37g/L were achieved, respectively. By adjusting the ratio of cellulases to xylanase, the TFSY reached a maximum of 0.5213g/g when the ratio was 1:1, while the maximum TFSC of 17.71g/L was achieved when the ratio was 1:4.