Optimized bioethanol production from Lemna minuta biomass harvested from polluted water via acid and enzymatic hydrolysis

The potential of fast-growing poplar species was evaluated for bioethanol production. The yields of glucose and xylose from acid and enzymatic hydrolysis were compared. The hydrolysis processes were performed on raw and extracted wood. The extracted wood was obtained by action of a chloroform and 96% ethanol (93:7 w/w) mixture. Additionally, to enhance the enzymatic hydrolysis efficiency, a liquid hot water (LHW) pretreatment was used. The acid hydrolysis turned out to be a good method to verify the biomass potential for bioethanol production. After acid hydrolysis of raw and extracted biomass, high total sugars yields were obtained (between 626.2 to 808.5 mg/g raw or extracted biomass), while in the case of enzymatic hydrolysis the total sugars yields were very low (between 45.5 to 68.9 mg/g raw or extracted biomass). The LHW pretreatment greatly enhanced the enzymatic digestibility of the studied wood. The average glucose yield from enzymatic hydrolysis was up to 602.0 mg/g pretreated biomass and was higher than that from acid hydrolysis (the maximum yield was 566.9 mg/g extracted biomass). As a result of the LHW pretreatment, up to 91.3% of the hemicelluloses were removed from the solid fraction. From the obtained glucose and xylose results, it was concluded that Populus trichocarpa wood had a higher potential for bioethanol production than P. deltoides x maximowiczii wood. The presence of extractives (low molecular substances) in raw poplar wood (up to 2.8%) had a low impact on the yield from acid and enzymatic hydrolysis.

The work is devoted to the application of biotechnological complex for the processing of plant raw materials and agricultural waste. The complex includes equipment for raw material preparation, acid and enzymatic hydrolysis. The research is focused on studying the kinetics of these processes and optimising process parameters to maximise the yield of valuable products. Experimental results show significant differences in the efficiency of acid and enzymatic hydrolysis. Acid hydrolysis, especially at high temperatures and pressures, shows high conversion of biomass to reducing sugars, but leads to the formation of by-products. In contrast, enzymatic hydrolysis provides more selective cleavage and fewer by-products, although it requires more expensive enzymes. Comparison with traditional wheat processing methods confirms the advantages of the proposed integrated technology, which provides a significant increase in the yield of target products such as glucose-fructose syrup and starch. The developed complex can be used for research and training of specialists in the field of biotechnology, contributing to the development of innovative solutions in the agro-industrial sector.

To effectively valorize agricultural waste (sugarcane bagasse) through biorefinery process, pretreatment which can be carried out in several ways is inevitable. This study explored the effects of chemical (acid and alkaline) and hydrothermal (steaming and autoclave) pretreatment methods on reducible sugar and ethanol yield from sugarcane bagasse. Acid pretreatment chemicals which include hydrogen peroxide and acetic acid were mixed together with sugarcane residue and heated at 85 oC for one hour. In alkaline pretreatment sodium hydroxide was mixed with the sugarcane waste and allow to incubate at 50 oC for one hour. The steaming approach involved using a steam distillation equipment. The sugarcane bagasse was first placed in a steam bag and then into a steam distillation unit which was steamed over a heating mantle for an hour. Autoclave pretreatment method used a stove type autoclave to disintegrate the processed sugarcane residue at 121oC. Each of these pretreated samples underwent independent hydrolysis and simultaneous saccharification and fermentation operations. Sugar yield was determined by the 3,5-dinitrosalicylic acid method, whereas the bioethanol yield was determined from refractometer readings. Sugarcane bagasse pretreated with acids gave a sugar yield of 995.567 mg/l and ethanol concentrations of 1.7303% in both enzymatic and acid hydrolysis, and 2.0758% ethanol concentration in simultaneous saccharification and fermentation process. Alkaline-pretreated sample gave a fermentable sugar yield of 441.2591 mg/l with 0.8655%, 0.6938%, and 1.73033% ethanol concentrations from enzymatic hydrolysis, acid hydrolysis and simultaneous saccharification and fermentation processes respectively. Steaming yielded 913.4849 mg/l of fermentable sugar, whereas the ethanol concentrations in the enzymatic hydrolysis, acid hydrolysis and simultaneous saccharification and fermentation methods were 1.2121%, 0.6938%, and 0.8666% respectively. Autoclave pretreatment resulted in a fermentable sugar yield of 800.9 mg/l with ethanol concentration of 1.3848% in both the enzymatic and acid hydrolysis, while that of simultaneous saccharification and fermentation was 1.0393%.

Cellulose nanocrystals (CNCs) have become valued bionanomaterials with enormous potential to bring fundamental changes and benefits to society. We evaluated the techno‐economic viability of using sulfuric acid and enzymatic hydrolysis technologies to produce CNCs from bleached eucalyptus Kraft pulp (BEKP) in stand‐alone facilities. Experiments were performed on the enzymatic and acid hydrolysis of BEKP and the separation and isolation of the generated CNCs. The results obtained were used to determine reaction yields and compositions through the process stages and to build mass balances for the production of CNCs via acid and enzymatic hydrolysis. We used the process data that were generated to simulate and scale up process models of the production of CNCs using Aspen Plus. Techno‐economic analyses of the simulated processes were performed using Aspen Process Economic Analyzer to generate capital and operating cost estimates. At an estimated minimum selling price (MSP) of $10 031/dry tonne of CNCs, the production of CNCs via acid hydrolysis can be technically and economically competitive. Further research and process optimization efforts should focus on low‐cost technologies that minimize water use and on sulfuric acid recovery technologies that lead to lower production costs. The production of CNCs via enzymatic hydrolysis requires a low capital investment. However, due to its low reaction yield, a reflection of the still early stage of process development, the production cost of the enzymatic CNCs, with an MSP of $65 740 dry tonne of CNCs t–1, is too high to be commercially attractive. Nonetheless, the low capital cost of producing CNCs by using enzymatic hydrolysis indicates that the process may be profitable if the enzymatic hydrolysis yield is drastically improved. Research efforts towards developing an enzyme cocktail designed and optimized specifically for CNCs production and the introduction of an efficient and low‐cost pretreatment stage prior to enzymatic hydrolysis to increase the accessibility of enzymes to cellulose may improve the hydrolysis yield. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

The aim of this work was the optimization of the enzyme hydrolysis of potato peel residues (PPR) for bioethanol production. The process included a pretreatment step followed by an enzyme hydrolysis using crude enzyme system composed of cellulase, amylase and hemicellulase, produced by a mixed culture of Aspergillus niger and Trichoderma reesei. Hydrothermal, alkali and acid pretreatments were considered with regards to the enhancement of enzyme hydrolysis of potato peel residues. The obtained results showed that hydrothermal pretreatment lead to a higher enzyme hydrolysis yield compared to both acid and alkali pretreatments. Enzyme hydrolysis was also optimized for parameters such as temperature, pH, substrate loading and surfactant loading using a response surface methodology. Under optimized conditions, 77 gL-1 of reducing sugars were obtained. Yeast fermentation of the released reducing sugars led to an ethanol titer of 30 gL-1 after supplementation of the culture medium with ammonium sulfate. Moreover, a comparative study between acid and enzyme hydrolysis of potato peel residues was investigated. Results showed that enzyme hydrolysis offers higher yield of bioethanol production than acid hydrolysis. These results highlight the potential of second generation bioethanol production from potato peel residues treated with onsite produced hydrolytic enzymes. © 2017 American Institute of Chemical Engineers Biotechnol. Prog., 33:397-406, 2017.

BackgroundThe efficiency of enzymatic hydrolysis is reduced by the structural properties of cellulose. Although efforts have been made to explain the mechanism of enzymatic hydrolysis of cellulose by considering the interaction of cellulolytic enzymes with cellulose or the changes in the structure of cellulose during enzymatic hydrolysis, the process of cellulose hydrolysis is not yet fully understood. We have analysed the characteristics of the complex supramolecular structure of cellulose on the nanometre scale in terms of the spatial distribution of fibrils and fibril aggregates, the accessible surface area and the crystallinity during enzymatic hydrolysis. Influence of the porosity of the substrates and the hydrolysability was also investigated. All cellulosic substrates used in this study contained more than 96% cellulose.ResultsConversion yields of six cellulosic substrates were as follows, in descending order: nano-crystalline cellulose produced from never-dried soda pulp (NCC-OPHS-ND) > never-dried soda pulp (OPHS-ND) > dried soda pulp (OPHS-D) > Avicel > cotton treated with sodium hydroxide (cotton + NaOH) > cotton.ConclusionsNo significant correlations were observed between the yield of conversion and supramolecular characteristics, such as specific surface area (SSA) and lateral fibril dimensions (LFD). A strong correlation was found between the average pore size of the starting material and the enzymatic conversion yield. The degree of crystallinity was maintained during enzymatic hydrolysis of the cellulosic substrates, contradicting previous explanations of the increasing crystallinity of cellulose during enzymatic hydrolysis. Both acid and enzymatic hydrolysis can increase the LFD, but no plausible mechanisms could be identified. The sample with the highest initial degree of crystallinity, NCC-OPHS-ND, exhibited the highest conversion yield, but this was not accompanied by any change in LFD, indicating that the hydrolysis mechanism is not based on lateral erosion.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0236-9) contains supplementary material, which is available to authorized users.

Wildflower mixtures for bioethanol production - Pretreatment and enzymatic hydrolysis

Sugar cane bagasse and corn stalks are rich in lignocellulose, which can be degraded into monosaccharides through enzymatic hydrolysis. Appropriate pretreatment methods can effectively improve the efficiency of lignocellulose enzymatic hydrolysis. To enhance the efficiency of enzymatic hydrolysis, thread rolling pretreatment as a physical pretreatment was applied in this study. The influence of raw material meshes size after pretreatment was also taken as the research target. Specific surface area analysis, Scanning electron microscope (SEM), X-rays diffraction (XRD), and Fourier transform infrared (FT-IR) were used for characterizations. The results showed that, the total monosaccharide recovery rates of the raw materials, 20–40 mesh, 40–60 mesh, and 60–80 mesh enzymolysis substrates were 17.6%, 34.58%, 37.94%, and 50.69%, respectively. The sample after pretreatment showed a better recovery of monosaccharide than that of the raw material. Moreover, the enzymolysis substrates with a larger mesh exhibited a higher recovery of monosaccharide than that of the enzymolysis substrates with smaller meshes. This indicated that thread rolling pretreatment can effectively improve the efficiency of enzymatic hydrolysis.

Sugarcane is a C4 perennial grass able to efficiently convert light energy into biomass. Bagasse, the fibrous waste product of sugar production, and biomass from high-fiber sugarcane varieties are important feedstocks for replacing fossil carbon in the production of fuels and other chemicals. Enzymatic hydrolysis can be used to convert the cellulose and hemicellulose components of the biomass into fermentable sugars. These sugars can then be fermented into ethanol and other chemicals using microbial organisms and catalysts. However, enzymatic hydrolysis is inefficient due to the recalcitrant nature of the secondary cell wall structure in which the cellulose and hemicellulose are located. Costly pretreatments are required to break down this structure prior to enzymatic hydrolysis in order to achieve high sugar yields. To reduce costs, genetic modification of biomass composition is a promising strategy for increasing the degradability of the biomass. The aims of this thesis were to identify the biomass components that can be manipulated to increase enzymatic hydrolysis efficiency and to discover genes and markers associated with one of these components that can be targeted for rapid improvement of this trait.Enzymatic hydrolysis efficiency and biomass composition were measured in leaf and culm tissues of sugarcane genotypes that varied in their fiber makeup. Tissues were left untreated or were pretreated using one of three methods (dilute acid, ionic liquid and hydrothermal) in order to understand how composition affects hydrolysis yields after various pretreatments. Interestingly, leaf tissues had sugar yields that were 1.5-fold those of the culm indicating that the composition of leaves is more susceptible to hydrolysis than that of the culm. Thus, leaf trash could be a useful resource for making biofuels and bioproducts. Additionally, genotypes performed differently depending on the pretreatment, indicating that pretreatment is an important consideration when identifying traits that impact enzymatic hydrolysis. A path analysis revealed that acid-insoluble lignin (AIL) content, syringyl to guaiacyl (S/G) ratio and xylan content had the greatest negative effects on enzymatic hydrolysis efficiency while acid-soluble lignin (ASL) and glucan content had strong positive influences. Therefore, these traits should be the main focus for genetic engineering and breeding sugarcane for utilization of the lignocellulosic fraction for a wide range of end-use applications.S/G ratio was further investigated using a differential expression analysis to determine genes that may be targeted for genetic modification of the trait. Over 2000 transcripts were differentially expressed (DE) between two groups, each consisting of six sugarcane genotypes, that contrasted for S/G ratio. Several DE transcripts corresponded to enzymes in the lignin biosynthesis pathway including caffeic acid O-methyltransferase (COMT), cinnamyl alcohol dehydrogenase (CAD), 4- coumarate:CoA ligase (4CL) and cinnamoyl-CoA reductase (CCR). Other DE transcripts encoded transporters, dirigent proteins and regulatory proteins, such as, transcription factors, F-box proteins ii and mediator complex subunits. The frequencies of single nucleotide polymorphisms (SNPs) were also compared between the two groups of genotypes to discover alleles that were associated with lignin composition. Over 2000 SNP loci across 787 unique transcripts encoding phenylpropanoid pathway enzymes, dirigent proteins, cell wall-related transcription factors and F-box proteins had group-specific expression. Overall, the DE transcripts and alleles with group-specific expression represent promising targets and genetic markers for altering the lignin composition in sugarcane.

Paddy straw (PS), a by-product of rice production, has a large volume, low economic value, and environmental impact due to burning, contributing to pollution and health hazards. This manuscript highlights the combined effect of acid treatments and enzymatic hydrolysis of paddy straw to produce fermentable hydrolysate, a potential biofuel. This study uses response surface methodology (RSM) with a Box–Behnken design to optimize process parameters (acid concentration, temperature, and duration of hydrolysis), thereby improving the efficiency of converting paddy straw into fermentable sugars. The efficacy of pretreatment was evaluated based on cellulose content and lignin reduction. The optimal conditions of 1% H2SO4, 80 °C, and 20 min resulted in effective cellulose enrichment (95.4%) and lignin reduction (38.2%), promoting efficient enzymatic hydrolysis. The enzymatic hydrolysis used cellulase from Trichoderma reesei, yielding high glucose concentrations of 225.2 mg glucose ml−1 g−1 paddy straw. Using Brunauer–Emmett–Teller (BET) analysis and morphology of pretreated and raw PS samples, the surface modification was validated for the optimized hydrolysis conditions. Surface area and pore volume for optimized condition decreased by 58.6% and 25% respectively. However, mean pore diameter increased by 87.9%. Herein, this study offers a more efficient, optimized, and sustainable pathway for converting paddy straw into biofuel using cellulase, with broader implications for agricultural waste management and renewable energy production.Graphical

Abstract. Purwoko Tj, Sari SLA, Mahadjoeno E, Sunarto. 2017. Bioethanol production from rice and corn husks after enzymatic and microbes hydrolysis and yeast fermentation. Bioteknologi 14: 19-23. Bioethanol is a renewable resource that can be produced from fermented cellulosic biomass. The use of lignocellulosic materials from agricultural wastes provides a low-cost fermentative substrate. Lignocellulosic ethanol production involves acid or enzymatic hydrolysis. The enzymatic hydrolysis cost higher, however in environmental issue this step is favorable. The purpose of this research was to compare bioethanol production after microbes and cellulosic enzymes hydrolysis following yeast, Saccharomyces cerevisiae, fermentation from rice and corn husks. The rice and corn husks (1 kg) were each suspended in water until the volumes reached 5 L. The sample mixtures were treated with 2.5 mg/L cellulases, 5 g/L multienzymes, and 5 mL/L EM4 respectively. The mixtures were stirred for 24 hours at pH 5.7 and 35°C. After hydrolysis, the samples (100 mL) were treated by 1, 2, and 3 % w/v Baker’s yeasts. The samples were fermented with incubator shaking for 6 days at 30°C, 90 rpm, and pH 6.5. Sugar concentrations were determined by dinitrosalicylic acid (DNS) colorimetric method. Bioethanol production and specific gravity method were then compared to IAOC Ethanol Table. Sugar concentrations and bioethanol production after multienzymes hydrolysis of rice and corn husks. There were 6.54-6.81 mg/mL and 3.17-3.54 mg/mL, respectively. Sugar concentrations of rice and corn husks after multienzymes hydrolysis treatment was higher than EM4 and cellulases hydrolysis treatments. Therefore, bioethanol productions of rice and corn husks after multienzymes hydrolysis and yeasts after 2 days fermentation were higher than the others.

Date Palm Byproducts for Green Fuels and Bioenergy Production

In order to explore the effect of additives on enzymatic hydrolysis of lignocellulose biomass, the effect of two different additives, Triton X-100 (TX-100) and Bovine serum albumin (BSA), enzyme dosages, and additive concentrations on enzymatic hydrolysis to obtain fermentable sugar using cellulose extracted from wheat straw (WS) as the substrate was investigated in this study. An enzymatic hydrolysis kinetic model was used to successfully describe the enzymatic hydrolysis in a heterogeneous system. Fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM) were used to determine the effect of extraction and enzymatic hydrolysis on the composition and structure of the samples. The results showed that the total reducing sugar concentration of the raw was 1.535g/L at 120h, but that of the extracted cellulose (EC) increased to 5.087g/L at 120h, indicating that EC from WS is more conducive to enzymatic hydrolysis compared with the raw. The total reducing sugar concentration with the addition of the TX-100 was 6.737g/L at 120h, which was greater than that with the addition of the BSA (5.728g/L at 120h), indicating that the addition of two additives improved the enzymatic hydrolysis efficiency, especially TX-100. The kinetic studies showed that the initial enzymatic hydrolysis reaction rate (Km) of the EC was more than four times greater than that of the raw. The Km of the EC added with TX-100 and BSA were increased by 29.50% and 22.89% compared with that of the EC without the addition of additive. The addition of additives is an effective method for enhancing enzymatic hydrolysis efficiency and fermentable sugar production from lignocellulosic biomass.

The sialic acid of gangliosides not containing GalNAc (i.e., GM3, GD3) is readily hydrolyzed either enzymatically by sialidases or chemically in acid conditions. On the other hand, in gangliosides having the sialic acid on the internal galactose residue linked to GalNAc (i.e., GM1, GM2) the Neu5Ac is largely resistant to acid or enzymatic hydrolysis. In the present work GM1 (NH4+), GM1(H+), and several de-acetylated derivatives in the sialic acid and in both sialic acid and N-acetylgalactosamine moieties were prepared. Studies by counterion exchange with DEAE-Sephadex A-25 and Dowex 50WX8, acid-base titration, and acid or enzymatic hydrolysis with sialidases were performed on these derivatives. Our results provide cumulative evidence supporting that a hydrogen bonding interaction between the hydrogen atom of un-ionized carboxyl group in Neu5Ac and the oxygen atom of the carbonyl group in GalNAc reduces the dissociation of the Neu5Ac carboxyl group and impairs its enzymatic and acid hydrolysis. In addition, our results suggest that the enzymatic hydrolysis of the ionized form of sialic acid in GM1(Na+) and GM1(NH4+) is impaired by a second hydrogen bonding interaction between the proton of the acetamide group in GalNAc and the carbonyl moiety of the carboxyl group of the Neu5Ac.

Comparison of enzymatic and acid hydrolysis of bound flavor compounds in model system and grapes