MDPI - Publisher of Open Access Journals

17 pages, 3336 KiB

Open AccessArticle

A Comparative Study of Various Pretreatment Approaches for Bio-Ethanol Production from Willow Sawdust, Using Co-Cultures and Mono-Cultures of Different Yeast Strains

by Imen Ben Atitallah, Georgia Antonopoulou, Ioanna Ntaikou, Amaia Soto Beobide, Vassilios Dracopoulos, Tahar Mechichi and Gerasimos Lyberatos

Molecules 2022, 27(4), 1344; https://doi.org/10.3390/molecules27041344 - 16 Feb 2022

Cited by 13 | Viewed by 3115

Abstract

The effect of different pretreatment approaches based on alkali (NaOH)/hydrogen peroxide (H₂O₂) on willow sawdust (WS) biomass, in terms of delignification efficiency, structural changes of lignocellulose and subsequent fermentation toward ethanol, was investigated. Bioethanol production was carried out using the conventional yeast Saccharomyces cerevisiae, as well as three non-conventional yeasts strains, i.e., Pichia stipitis, Pachysolen tannophilus, Wickerhamomyces anomalus X19, separately and in co-cultures. The experimental results showed that a two-stage pretreatment approach (NaOH (0.5% w/v) for 24 h and H₂O₂ (0.5% v/v) for 24 h) led to higher delignification (38.3 ± 0.1%) and saccharification efficiency (31.7 ± 0.3%) and higher ethanol concentration and yield. Monocultures of S. cerevisiae or W. anomalus X19 and co-cultures with P. stipitis exhibited ethanol yields in the range of 11.67 ± 0.21 to 13.81 ± 0.20 g/100 g total solids (TS). When WS was subjected to H₂O₂ (0.5% v/v) alone for 24 h, the lowest ethanol yields were observed for all yeast strains, due to the minor impact of this treatment on the main chemical and structural WS characteristics. In order to decide which is the best pretreatment approach, a detailed techno-economical assessment is needed, which will take into account the ethanol yields and the minimum processing cost. Full article

(This article belongs to the Special Issue Efficient Technology for the Pretreatment of Biomass III)

► Show Figures

Figure 1

17 pages, 6965 KiB

Open AccessArticle

Biochemical Conversion of Lignocellulosic Biomass from Date Palm of Phoenix dactylifera L. into Ethanol Production

by Yousra Antit, Inmaculada Olivares, Moktar Hamdi and Sebastián Sánchez

Energies 2021, 14(7), 1887; https://doi.org/10.3390/en14071887 - 29 Mar 2021

Cited by 9 | Viewed by 2398

Abstract

Cellulosic fibers from date palm are among the most promising lignocellulose feedstock for biorefinery purposes. The world production is between 1.9 and 2.4 million t/year. Initially, a pretreatment with dilute-sulphuric acid of these fibers was performed using a response surface methodology, with temperature and process time as factors. The aim is to produce bioethanol from young and old fibers from date palm, Phoenix dactylifera L. Optimal thermochemical pretreatment conditions for both fibers palms were 220 °C in hydrothermal conditions (without acid); in these conditions pretreated young fibers presented a maximum content in holocelluloses of 45.18% and old fibers 61.97%. Subsequently, during the enzymatic hydrolysis a maximum yield of total reducing sugars (TRS) was reached, 46.32 g/100 g for pretreated dry young fibers and 48.54 g/100 g for pretreated dry old fibers. After enzymatic saccharification, hydrolysates were fermented by Pachysolen tannophilus (ATCC 32691) to ethanol, reaching yields (Y_E/TRS) of 37.94 g ethanol/100 g of TRS for young fibers and 35.84 g ethanol/100 g of TRS for old fibers. Globally, considering the full process, in the fermentation of the hydrolysates, a yield (Y_E) of 10.64 g ethanol/100 g of dry young fibers and 10.88 g ethanol/100 g of dry old fibers was reached. Full article

(This article belongs to the Section B: Energy and Environment)

► Show Figures

Figure 1

17 pages, 2197 KiB

Open AccessArticle

Ethanol Production from Olive Stones through Liquid Hot Water Pre-Treatment, Enzymatic Hydrolysis and Fermentation. Influence of Enzyme Loading, and Pre-Treatment Temperature and Time

by Manuel Cuevas, Juan F. García Martín, Vicente Bravo and Sebastián Sánchez

Fermentation 2021, 7(1), 25; https://doi.org/10.3390/fermentation7010025 - 17 Feb 2021

Cited by 13 | Viewed by 3972

Abstract

Olive table industry, olive mills and olive pomace oil extraction industries annually generate huge amounts of olive stones. One of their potential applications is the production of bioethanol by fractionation of their lignocellulose constituents and subsequent fermentation of the released sugars using yeasts. In this work, we studied the influence of temperature (175–225 °C) and residence time (0–5 min) in the liquid hot-water pre-treatment of olive stones as well as the initial enzyme loading (different mixtures of cellulases, hemicellulases and β–glucosidases) in the later enzymatic hydrolysis on the release of fermentable sugars. The Chrastil’s model was applied to the d-glucose data to relate the severity of pre-treatment to enzyme diffusion through the pre-treated cellulose. Finally, the hydrolysate obtained under the most suitable conditions (225 °C and 0 min for pre-treatment; 24 CE initial enzyme concentration) was fermented into ethanol using the yeast Pachysolen tannophilus ATCC 32691. Considering the overall process, 6.4 dm³ ethanol per 100 kg olive stones were produced. Full article

(This article belongs to the Special Issue Food Wastes: Feedstock for Value-Added Products: 2nd Edition)

► Show Figures

Figure 1

18 pages, 1627 KiB

Open AccessArticle

Designing Efficient Processes for Sustainable Bioethanol and Bio-Hydrogen Production from Grass Lawn Waste

by Georgia Antonopoulou

Molecules 2020, 25(12), 2889; https://doi.org/10.3390/molecules25122889 - 23 Jun 2020

Cited by 16 | Viewed by 3127

Abstract

The effect of thermal, acid and alkali pretreatment methods on biological hydrogen (BHP) and bioethanol production (BP) from grass lawn (GL) waste was investigated, under different process schemes. BHP from the whole pretreatment slurry of GL was performed through mixed microbial cultures in simultaneous saccharification and fermentation (SSF) mode, while BP was carried out through the C5yeast Pichia stipitis, in SSF mode. From these experiments, the best pretreatment conditions were determined and the efficiencies for each process were assessed and compared, when using either the whole pretreatment slurry or the separated fractions (solid and liquid), the separate hydrolysis and fermentation (SHF) or SSF mode, and especially for BP, the use of other yeasts such as Pachysolen tannophilus or Saccharomyces cerevisiae. The experimental results showed that pretreatment with 10 gH₂SO₄/100 g total solids (TS) was the optimum for both BHP and BP. Separation of solid and liquid pretreated fractions led to the highest BHP (270.1 mL H₂/g TS, corresponding to 3.4 MJ/kg TS) and also BP (108.8 mg ethanol/g TS, corresponding to 2.9 MJ/kg TS) yields. The latter was achieved by using P. stipitis for the fermentation of the hydrolysate and S. serevisiae for the solid fraction fermentation, at SSF. Full article

(This article belongs to the Special Issue Efficient Technology for the Pretreatment of Biomass III)

► Show Figures

Figure 1

11 pages, 736 KiB

Open AccessCommunication

The Process of Producing Bioethanol from Delignified Cellulose Isolated from Plants of the Miscanthus Genus

by Olga Kriger, Ekaterina Budenkova, Olga Babich, Stanislav Suhih, Nikolay Patyukov, Yakov Masyutin, Vyacheslav Dolganuk and Evgeny Chupakhin

Bioengineering 2020, 7(2), 61; https://doi.org/10.3390/bioengineering7020061 - 21 Jun 2020

Cited by 16 | Viewed by 4324

Abstract

Plants of the Miscanthus genus (Miscanthus Anderss.) have a unique index of biomass production in relation to the occupied area. Miscanthus plants can be attributed to promising second-generation raw materials for the production of bioethanol and biofuel. Miscanthus plants are characterized by a high cellulose content. Herein, we report the results of a study on the obtained delignified cellulose with subsequent processing into bioethanol using microbial communities. In the course of the study, the optimal conditions for the delignification of the initial plant material for cellulose were selected. Ethanol with a high degree of conversion was successfully obtained from the isolated delignified cellulose. The article describes the pilot technological scheme for the conversion of Miscanthus plant biomass to bioethanol involving the delignification stages, followed by the conversion of the resulting cellulose into bioethanol by a consortium of microorganisms. As a result of the study, it was found that delignification using trifluoroacetic acid leads to the production of cellulose of high purity. Bioethanol with a yield of 3.1% to 3.4% in terms of the initial amount of biomass was successfully obtained by a microorganism consortium of Saccharomyces cerevisiae M Y-4242/Pachysolen tannophilus Y-3269, and Scheffersomyces stipitis Y-3264. Full article

(This article belongs to the Special Issue Advances in Biomass Preprocessing and Pretreatments and Valorization to Energy)

► Show Figures

Figure 1

14 pages, 1902 KiB

Open AccessFeature PaperArticle

Acid and Enzymatic Fractionation of Olive Stones for Ethanol Production Using Pachysolen tannophilus

by Manuel Cuevas, Marwa Saleh, Juan F. García-Martín and Sebastián Sánchez

Processes 2020, 8(2), 195; https://doi.org/10.3390/pr8020195 - 6 Feb 2020

Cited by 19 | Viewed by 3498

Abstract

Olive stones are an abundant lignocellulose material in the countries of the Mediterranean basin that could be transformed to bioethanol by biochemical pathways. In this work, olive stones were subjected to fractionation by means of a high-temperature dilute-acid pretreatment followed by enzymatic hydrolysis of the pretreated solids. The hydrolysates obtained in these steps were separately subjected to fermentation with the yeast Pachysolen tannophilus ATCC 32691. Response surface methodology with two independent variables (temperature and reaction time) was applied for optimizing D-xylose production from the raw material by dilute acid pretreatment with 0.01 M sulfuric acid. The highest D-xylose yield in the liquid fraction was obtained in the pretreatment at 201 °C for 5.2 min. The inclusion of a detoxification step of the acid prehydrolysate, by vacuum distillation, allowed the fermentation of the sugars into ethanol and xylitol. The enzymatic hydrolysis of the pretreated solids was solely effective when using high enzyme loadings, thus leading to easily fermentable hydrolysates into ethanol. The mass macroscopic balances of the overall process illustrated that the amount of inoculum used in the fermentation of the acid prehydrolysates strongly affected the ethanol and xylitol yields. Full article

(This article belongs to the Special Issue Production of Biofuels and Numerical Modeling of Chemical Combustion Systems)

► Show Figures

Figure 1

Search Results (6)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI

Saved Queries

Search Filter Reset All

Years

Feature Papers

Subjects

Journals

Article Types

Countries / Regions

Search Results (6)

Further Information

Guidelines

MDPI Initiatives

Follow MDPI