Enzymatic hydrolysis and fermentation strategies for the biorefining of pine sawdust

This work aims to evaluate second-generation bioethanol production from the soda-ethanol pulp of pine sawdust via two strategies: separate hydrolysis and fermentation and simultaneous saccharification and fermentation. A kinetics study of the enzymatic hydrolysis of separate hydrolysis and fermentation was included as a design tool. Three soda-ethanol pulps (with different chemical compositions), Cellic® Ctec2 cellulolytic enzymes, and Saccharomyces cerevisiae IMR 1181 (SC 1181) yeast were employed. The obtained kinetic parameters were as follows: an apparent constant (k) of 11.4 h-1, which represents the link frequency between cellulose and cellulase; a Michaelis-Menten apparent constant (KM) of 23.5 gL-1, that indicates the cellulose/cellulase affinity; and the apparent constant of inhibition between cellulose-glucose and cellulase (KI), which was 2.9 gL-1, 3.1 gL-1, and 6.6 gL-1 for pulps 1, 2, and 3, respectively. The kinetic model was applicable, since the calculated glucose values fit the experimental values. High bioethanol yields were obtained for pulp 3 in the separate hydrolysis and fermentation and simultaneous saccharification and fermentation processes (89.3% and 100% after 13 h and 72 h, respectively).

Enzymatic Hydrolysis and Fermentation of Banana Pseudostem Hydrolysate to Produce Bioethanol

Banana pseudostem (BPS) is an agricultural waste with a high holocellulose content, which, upon hydrolysis, releases fermentable sugars that can be used for bioethanol production. Different pretreatment methods, namely, 3% (w/v) NaOH, 5% (v/v) H2SO4, and liquid hot water, applied on the BPS resulted in the availability of 52%, 48%, and 25% cellulose after treatment, respectively. Saccharification of the pretreated BPS with 10 FPU/g dry solids (29.3 mg protein/g d.s) crude enzyme from Trichoderma harzianum LMLBP07 13-5 at 50°C and a substrate loading of 10 to 15% released 3.8 to 21.8 g/L and from T. longibrachiatum LMLSAUL 14-1 released 5.4 to 43.5 g/L glucose to the biomass. Ethanol was produced through separate hydrolysis and fermentation (SHF) of alkaline pretreated BPS hydrolysate using Saccharomyces cerevisiae UL01 at 30°C and 100 rpm. Highest ethanol produced was 17.6 g/L. Banana pseudostem was shown as a potentially cheap substrate for bioethanol production.

Bioethanol Production from Cellulose-Rich Corncob Residue by the Thermotolerant Saccharomyces cerevisiae TC-5

This study aimed to select thermotolerant yeast for bioethanol production from cellulose-rich corncob (CRC) residue. An effective yeast strain was identified as Saccharomyces cerevisiae TC-5. Bioethanol production from CRC residue via separate hydrolysis and fermentation (SHF), simultaneous saccharification and fermentation (SSF), and prehydrolysis-SSF (pre-SSF) using this strain were examined at 35–42 °C compared with the use of commercial S. cerevisiae. Temperatures up to 40 °C did not affect ethanol production by TC-5. The ethanol concentration obtained via the commercial S. cerevisiae decreased with increasing temperatures. The highest bioethanol concentrations obtained via SHF, SSF, and pre-SSF at 35–40 °C of strain TC-5 were not significantly different (20.13–21.64 g/L). The SSF process, with the highest ethanol productivity (0.291 g/L/h), was chosen to study the effect of solid loading at 40 °C. A CRC level of 12.5% (w/v) via fed-batch SSF resulted in the highest ethanol concentrations of 38.23 g/L. Thereafter, bioethanol production via fed-batch SSF with 12.5% (w/v) CRC was performed in 5-L bioreactor. The maximum ethanol concentration and ethanol productivity values were 31.96 g/L and 0.222 g/L/h, respectively. The thermotolerant S. cerevisiae TC-5 is promising yeast for bioethanol production under elevated temperatures via SSF and the use of second-generation substrates.

Aqueous Ammonia With Sodium Sulfite Pretreatment For Enhancing Enzymatic Saccharification and Bioethanol Production of Sugarcane Bagasse

Background: Bioethanol is considered as a promising alternative fuel. Lignocellulosic biomass can be used for the production of bioethanol, but its recalcitrant structure makes it difficult to be utilized. Thus, proper pretreatment is a crucial step to break this structure and enhance enzymatic saccharification. Aqueous ammonia with sodium sulfite pretreatment (AAWSSP) was first applied to enhance the enzymatic saccharification and bioethanol production of sugarcane bagasse (SCB) in this research.Results: Response surface methodology was applied to optimize the conditions of pretreatment. Under optimal parameters, 16.92 g/L of total sugar concentration (P1 SCB: 202.08℃, 11.06% aqueous ammonia, 13.37% sodium sulfite, 1.22 h) and 0.51 g/g of total sugar yield (P2 SCB: 199.47℃, 10.17% aqueous ammonia, 13.11% sodium sulfite, 1.17 h) were achieved, respectively. The results of ethanol fermentation showed that separate hydrolysis and fermentation performed better than that of simultaneous saccharification and fermentation, and the maximum ethanol yields of 143.30 g/kg for P1 SCB and 145.33 g/kg for P2 SCB, were obtained, respectively. Conclusions: This research indicated that aqueous ammonia and sodium sulfite in pretreatment solution might have a synergistic effect on delignification and enzymatic saccharification. AAWSSP might be a prospective method for enhancing enzymatic saccharification and bioethanol production of SCB, which provided new guidance for the bio-refinery of lignocellulose.

Production of green bacterial cellulose nanofibers by utilizing renewable resources of algae in comparison with agricultural residue

Bacterial Cellulose (BC) was synthesized through utilizing algae as a sustainable and renewable carbon source in comparison with agriculture residues (i.e., Wheat Straws (WS)). BC was produced in separate hydrolysis and fermentation method (SHF) using Gluconacetobacter xylinum (G.xylinum). Results for the individual and total sugars were analyzed in comparison with corresponding results from WS hydrolysis. Results show that highest total sugars content was obtained with algae samples that were hydrolyzed using enzymes (Cellulase, β-glycosidase, and Xylanase) and produced 27.58 g/L. Similarly, WS hydrolysis under same conditions produced 52.12 g/L. The lowest total sugars production was obtained with algae sample that was hydrolyzed using 1% of acid at 121°C. Produced sugars were utilized in SHF to produce BC, with highest production of 4.86 g/L BC was achieved with algae sample that went through enzymatic hydrolysis. The equivalent production that was obtained from WS hydrolysis was 10.6 g/L Results obtained from individual sugars indicated that among all individual sugars glucose was maximum consumed i.e. 80-85%of glucose sugar was consumed where the lowest was arabinose which was only 50% consumed during fermentation. The lower production of BC using algae compared to WS (approximately half) as algae we used was unprocessed means it had oil content in it. About 30-60% of algae dry weight was utilized for production of oil and rest amount of feedstock was only used for hydrolysis and fermentation.

Production of Green Biocellulose Nanofibers Through Utilizing Agricultural Wastes

In the present study, the green Biocellulose Nanofibers (BC), a vitally emerging biomaterial, was produced by fermentation of wheat straw (WS), as a widely available agricultural waste, using. Two different fermentation methods were used; Separate Hydrolysis and Fermentation (SHF), and Simultaneous Saccharification and Fermentation (SSF). Different acidic and enzymatic WS pretreatment conditions were used to understand the effect of pretreatment conditions on BC production. Afterward, sugar hydrolsates were simultaneously or separately inoculated with Gluconacetobacter Xylinum bacterium (i.e., for SSF and SHF, respectively), at optimum production conditions in shake flasks for 7 days to produce the biocellulose nanofibers. BC productions of 9.7 g/L in SHF and 10.8 g/L in SSF were achieved when WS was pretreated with dilute acids. Enzymatic treatment of WS after acidic pretreatment increased sugars’ concentrations from the hydrolysis, which increased BC production in SHF to 10.6 g/L. However, enzymes in SSF broke cellulose I alpha linkage in BC and decreased its production compared to no enzymatic treatment. Results show that glucose extracted from WS (~55% of total sugars) was found essential for the cellular metabolism, while xylose (~28% of total sugars) was highly consumed during cells growth phase. Generally, increasing thermal treatment, time and temperature, resulted in increasing furfural concentration. This observed to inhibits bacterial cells growth and leads to lower nanofibers yield when exists at concentration higher than 1 g/L threshold. In general, results obtained in the present study demonstrate the ability of utilizing agricultural wastes in the fermentation production of BC. Such a step is expected to eliminate cost of expensive pure sugars as a carbon source in the fermentation. Also the study shows an improved production yield by using effective fermentation techniques as SSF compared to classical methods used in literature.

Production of Green Biocellulose Nanofibers Through Utilizing Agricultural Wastes

In the present study, the green Biocellulose Nanofibers (BC), a vitally emerging biomaterial, was produced by fermentation of wheat straw (WS), as a widely available agricultural waste, using. Two different fermentation methods were used; Separate Hydrolysis and Fermentation (SHF), and Simultaneous Saccharification and Fermentation (SSF). Different acidic and enzymatic WS pretreatment conditions were used to understand the effect of pretreatment conditions on BC production. Afterward, sugar hydrolsates were simultaneously or separately inoculated with Gluconacetobacter Xylinum bacterium (i.e., for SSF and SHF, respectively), at optimum production conditions in shake flasks for 7 days to produce the biocellulose nanofibers. BC productions of 9.7 g/L in SHF and 10.8 g/L in SSF were achieved when WS was pretreated with dilute acids. Enzymatic treatment of WS after acidic pretreatment increased sugars’ concentrations from the hydrolysis, which increased BC production in SHF to 10.6 g/L. However, enzymes in SSF broke cellulose I alpha linkage in BC and decreased its production compared to no enzymatic treatment. Results show that glucose extracted from WS (~55% of total sugars) was found essential for the cellular metabolism, while xylose (~28% of total sugars) was highly consumed during cells growth phase. Generally, increasing thermal treatment, time and temperature, resulted in increasing furfural concentration. This observed to inhibits bacterial cells growth and leads to lower nanofibers yield when exists at concentration higher than 1 g/L threshold. In general, results obtained in the present study demonstrate the ability of utilizing agricultural wastes in the fermentation production of BC. Such a step is expected to eliminate cost of expensive pure sugars as a carbon source in the fermentation. Also the study shows an improved production yield by using effective fermentation techniques as SSF compared to classical methods used in literature.

Production of green bacterial cellulose nanofibers by utilizing renewable resources of algae in comparison with agricultural residue

Bacterial Cellulose (BC) was synthesized through utilizing algae as a sustainable and renewable carbon source in comparison with agriculture residues (i.e., Wheat Straws (WS)). BC was produced in separate hydrolysis and fermentation method (SHF) using Gluconacetobacter xylinum (G.xylinum). Results for the individual and total sugars were analyzed in comparison with corresponding results from WS hydrolysis. Results show that highest total sugars content was obtained with algae samples that were hydrolyzed using enzymes (Cellulase, β-glycosidase, and Xylanase) and produced 27.58 g/L. Similarly, WS hydrolysis under same conditions produced 52.12 g/L. The lowest total sugars production was obtained with algae sample that was hydrolyzed using 1% of acid at 121°C. Produced sugars were utilized in SHF to produce BC, with highest production of 4.86 g/L BC was achieved with algae sample that went through enzymatic hydrolysis. The equivalent production that was obtained from WS hydrolysis was 10.6 g/L Results obtained from individual sugars indicated that among all individual sugars glucose was maximum consumed i.e. 80-85%of glucose sugar was consumed where the lowest was arabinose which was only 50% consumed during fermentation. The lower production of BC using algae compared to WS (approximately half) as algae we used was unprocessed means it had oil content in it. About 30-60% of algae dry weight was utilized for production of oil and rest amount of feedstock was only used for hydrolysis and fermentation.