Simultaneous Saccharification And Fermentation Research Articles

Bio-2,3-butanediol production from banana waste: Preliminary techno-economic evaluation of processing strategies

This study evaluates different fermentation strategies to produce 2,3-butanediol (2,3-BD) from banana industry waste, such as whole bananas (fruit + peels) and banana peels, selecting the most favorable from a technical and economic point of view. Both residues have enough free sugars (17.8 %–35.8 %), glucan (11.0 %–14.2 %) and hemicellulose (2.8 %–6.3 %), to be promising substrates for 2,3-BD fermentation. Saccharification was studied by comparing enzymatic hydrolysis, hydrothermal pretreatment, and hydrothermal pretreatment followed by enzymatic hydrolysis. Different fermentation scenarios were also compared regarding the 2,3-BD yield and productivity: Separate Hydrolysis and Fermentation (SHF), Simultaneous Saccharification and Fermentation (SSF), and direct fermentation without prior saccharification using Paenibacillus polymyxa DSM-365 as the fermenting microorganism. The results showed that the pretreatment step was not necessary to improve the release of fermentable sugars. Enzymatic hydrolysis was the most effective alternative for maximizing sugar recovery, reaching sugar concentrations of 18.1 g/L (recovery: 92.5 %) for banana peels and 33.3 g/L (recovery: ∼100 %) for whole bananas. The SSF strategy led to higher 2,3-BD concentrations of 15.0 g/L and 26.6 g/L for banana peels and whole bananas, respectively. The preliminary economic analysis indicated that SSF and direct fermentation could be the more cost-effective process alternatives for banana peels and whole bananas, respectively. Thus, it was demonstrated that banana waste is an interesting resource for the production of 2,3-BD. The bioprocess can be competitive when using a low-cost raw material and reducing the number of process steps compared to traditional technologies.

Simultaneous Saccharification and Fermentation (SSF) of Blended Organic Fertilizer from Yam and Sweet Potato Peels

This study shows the production of organic fertilizer by utilization of yam and sweet potatoes peels through Simultaneous Saccharification and Fermentation (SSF) Method. Samples are categorized into sun-dried, sundried and autoclaved, Heat-dried, heat-dried and autoclaved, the fermentation process is carried out using alpha amylase and saccharomyces cerevisiae. Investigation of mineral elements (N, Cd, P, Zn, Pb, As, K, Hg.), in the eight varieties of Organic Fertilizer produced shows concentration of Cadmium (Cd) ranges from 0.0015 mg/kg to 0.0033 mg/kg), Nitrogen (N) in Percentage ranges from 2.3450% to 3.8550%; Phosphorus (P) ranges from 2.345 mg/kg to 3.607 mg/kg; Zinc (Zn) ranges from 2.215 mg/kg to 6.335 mg/kg. Lead (Pb) ranges from 0.00 mg/kg to 0.0015 mg/kg, potassium (K) ranges from 3.952 mg/kg to 6.213 mg/kg; Mercury and Arsenic nil. The study shows that Sweet Potato Peel (SDSPP) contains high Cadmium and potassium compare to other organic fertilizer produced. Sundried and Autoclaved Yam Peel (SDAYP) contains high percentage of Nitrogen (N), Heat Dried and Autoclaved Sweet Potato Peel (HDASPP) contains low Nitrogen, Sundried and Autoclaved Sweet Potato Peel (SDASPP) contains low phosphorus, Sundried Yam Peel (SDYP), Sundried and Autoclaved Yam Peels (SDAYP), Heat Dried Sweet Potato Peel HDSPP and Heat Dried Sweet Potato Peel (HDSPP) has zero trace of Lead (Pb) making it free of food intoxication from heavy metals, SDYP contains high phosphorus. These indicate that the samples will make quality organic fertilizer because it contains high Nitrogen, Phosphorus and potassium (NPK) which are essential elements required in plant structures.

Simultaneous Saccharification and Fermentation for Isobutanol Production from Banana Peel

Each year, near 40 million tons of banana peels are discarded around the world. This plant biomass could potentially be utilized for energy production. Simultaneous saccharification and fermentation (SSF) is an effective method for producing biofuels from plant biomasses. Since SSF with enzymatic hydrolysis and fermentation are performed simultaneously in the same reactor, the production process is simpler than most existing methods. Here, we describe isobutanol production using SSF with hydrothermally treated banana peel samples and an Escherichia coli strain able to utilize glucose and xylose to produce isobutanol. To enhance the glucose and xylose concentrations, the reaction conditions for the enzymatic hydrolysis of plant biomass using two kinds of saccharification enzymes were optimized, including the enzyme unit ratio, reaction temperature and sample gram. When the optimized conditions for enzymatic hydrolysis were applied to SSF, the glucose and xylose produced from the hydrothermally treated samples were consumed, producing isobutanol. Moreover, the isobutanol concentration increased with an increasing initial culture pH, reaching 1.27 g/L at pH 6.5, which was consistent with the optimal initial culture pH for isobutanol production by this E. coli strain. Taken together, these results indicate that the established method is potentially useful for industrial isobutanol production.

Biorefinery-based sustainability assessment of macroalgae waste valorization to polylactic acid: Exergy and exergoeconomic perspectives

This study evaluated the exergetic and exergoeconomic performance of three L-lactic acid (L-LA) production scenarios. All three scenarios produced L-LA from red macroalgae waste, Eucheuma cottonii residue (ECR) with the same species of enzymes, and lactic acid bacteria (LAB). Scenario 1 is the biorefinery process for the L-LA. Scenario 2 is the biorefinery process for the L-LA with fertilizer production and wastewater treatment. Scenario 3 is the polylactic acid (PLA) biorefinery process with fertilizer production and wastewater treatment. From the study, the total production rate for L-LA was 5194 kg/hr, with a total consumption rate of 12079 kg/hr for ECR. In addition, the production rates of organic fertilizer and reused water were 1609 and 1233 kg/hr, respectively, for scenario 2. Then, the production rate of the PLA was 4142 kg/hr for scenario 3. From the comparison, the energy consumption was increased due to the increased demand for process and equipment (from 28272.53 kW to 30296.15 kW). From the exergetic analysis aspect, the highest contributor to the exergy loss was the simultaneous saccharification and fermentation (SSF) unit, totaling 18875.62 kW. For the exergoeconomic aspect, the SSF unit also contributed the highest exergy destruction cost rate (average 70%). The study results provide theoretical guidance for exergetic and economic performance improvement in future L-LA and PLA production.

A Comparison of ethanol production utilizing separated hydrolysis fermentation and simultaneous saccharification and fermentation methods applied to Tanduk banana peel waste

In 2021, Indonesia’s banana production is expected to reach 8.74 million tons. This substantial volume of bananas will generate a notable quantity of banana peel waste, constituting approximately one-third of the total banana fruit mass. Remarkably, banana peel waste retains 18.5% carbohydrates, which can be effectively converted into glucose, serving as a valuable feedstock for ethanol production. This research is focused on the ethanol production derived from Tanduk banana peel waste, employing a comparative analysis of the Separated Hydrolysis Fermentation (SHF) and Simultaneous Saccharification and Fermentation (SSF) techniques. Additionally, it explored varying raw material concentrations, specifically 200, 250, and 300 g/L. The SSF method integrated the use of cellulase enzymes, while the SHF method relied on HCl for the hydrolysis process. Microbial fermentation was facilitated by Saccharomyces cerevisiae, with a fermentation duration of 96 hours and sample collection at 12-hour intervals. The results demonstrated that higher concentrations of banana peel waste yield increased glucose production during the hydrolysis process, consequently leading to greater ethanol produced. The concentration of 300 g/L banana peel waste is optimal for producing ethanol in both procedures. However, the SHF approach demonstrates a superior ethanol concentration of 51%, surpassing the 33.7% achieved by the SSF method.

Co-valorization of discarded wood pinchips and sludge from the pulp and paper industry for production of advanced biofuels

Several lignocellulosic wastes are generated in the pulp and paper industry (PPI), such as small wood chips (pinchips) and paper sludge, presenting a high cellulose content suitable to be converted into biofuels or bio-products in a forest biorefinery scheme. In this work, two schemes of biorefinery were proposed for their valorization, processing small eucalyptus wood pinchips in two different strategies: (i) autohydrolysis at 230ºC, and (ii) autohydrolysis at 195ºC followed by organosolv process (47.7% ethanol-water, 198ºC for 60 min). More than 95% of cellulose was recovered in both schemes. In the combined process, 76% of delignification was achieved and 78% of xylan was solubilized as xylooligosaccharides. To reduce operational cost of lignocellulosic biomass-to-ethanol fermentation, the mixture of the treated eucalyptus pinchips from two processes with sludge was also proposed to increase the initial glucan content and to supply a rich source of nitrogen (present in the sludge). For that, two experimental designs were carried out for ethanol production by simultaneous saccharification and fermentation (SSF) process. Ethanol from SSF assays using sludge as co-substrate at 0.6 g of sludge/g of treated wood pinchips and 16 FPU/g of pretreated solids allowed to obtain 59 g/L (90% of conversion) and 46 g/L (96% of conversion) when blended with the wood from autohydrolysis and with the wood from autohydrolysis followed by organosolv, respectively. Overall, this study shows an alternative process valorization of biomasses derived from PPI for production of advanced biofuels and bio-products (such as xylooligosaccharides and lignin) contributing to achieving a circular economy.

Influence of Inhibitors from Microwave Pretreatment of Oil Palm Frond Pulping (OPFP) on Bioethanol Production

This research aims to analyze the influence of inhibitors from microwave pretreatment of oil palm frond pulping (OPFP) on the efficiency of bioethanol fermentation by S.cerevisiae in the simultaneous saccharification and fermentation (SSF) processes. OPFPs were achieved at different ages: 3-4, 4-7, 7-10, 10-20, and 20-25 years old. OPFP was pretreated with a microwave and sulfuric acid (MW/SF), microwave and hydrogen sulfide (MW/HP), and microwave and water (MW/W). The results showed that the main inhibitors formed during the pretreatment process of OPFP were acetic acid, furfural, 5-hydroxymethylfurfural (HMF), furfural, formic acid, and phenol. The pretreatment of OPFP with MW/W had the lowest concentrations of inhibitors compared to the other pretreatment methods. The highest bioethanol yields at all ages of OPFP were in the range of 0.41-0.42 g-bioethanol/g-glucose, corresponding to more than 80% fermentation efficiency. At these conditions, the concentrations of the acetic acid were 0.09-0.19 g/l, HMF =0, furfural =0, formic acid 0.05-0.28 g/l, and phenol 0.22-0.47 g/l. The MW/W was the suitable pretreatment of OPFP for bioethanol production due to the lowest to generate the inhibitor and high ethanol production yield.

Enzymatic hydrolysis of organosolv-pretreated corncob and succinic acid production by Actinobacillus succinogenes

In this study, the conversion of organosolv-treated corncob into monosaccharides through enzymatic saccharification was investigated, with the resulting monosaccharides being utilized as a carbon source to produce succinic acid. The synergy between the cellulase and xylanase provided 76% cellulose and 64% xylan digestibility at 50 °C and pH 5.2. In separate hydrolysis and fermentation (SHF), Actinobacillus succinogenes produced 12.7 g/L of succinic acid from the hydrolysate with 0.12 g/g yield based on the pretreated corncob. Simultaneous saccharification and fermentation (SSF) demonstrated better performance with 16 g/L succinic acid titer and 0.24 g/g yield, though SHF provided a higher production rate. The condition in the SSF (37 °C and pH near neutral) was suboptimal for the enzymes, thus the succinic acid production was limited by the saccharification step. These findings emphasize the potential of organosolv-treated corncob to serve as an enzymatic hydrolysis substrate without neutralization and detoxification, supplying glucose and xylose for succinic acid production by A. succinogenes.

CONVERSION OF PINEAPPLE PEEL GLUCOSE INTO BIOETHANOL USING SIMULTANEOUS SACCHARIFICATION AND FERMENTATION (SSF) METHOD AND SEPARATE HYDROLYSIS AND FERMENTATION (SHF) METHOD

This study aims to determine the bioethanol yield and characteristics from pineapple peel with two methods such as Simultaneous Saccharification and Fermentation (SSF) and Separate Hydrolysis and Fermentation (SHF). The percent yield of bioethanol produced from the fermentation of pineapple peel (Ananas comosus) with the Simultaneous Saccharification and Fermentation method was 63.50%, while the yield of bioethanol from the Separate Hydrolysis and Fermentation method was 58.75%. The physical characteristics of bioethanol pineapple peel waste using Simultaneous Saccharification and Fermentation method has a density of 0.8237 w/v whilst with Separate Hydrolysis and Fermentation is 0.8858 w/v. Furthermore, viscosity of bioethanol using Simultaneous Saccharification and Fermentation is 1.05 Cp whereas using Separate Hydrolysis and Fermentation is 1.02 Cp. Pineapple peel bioethanol method of Simultaneous Saccharification and Fermentation has concentration of 13% while Separate Hydrolysis and Fermentation method has concentration of 7.92%. FTIR spectra from SHF bioethanol missing the peak correlated with CH, CH3, and CO. These missing peaks is due to the high percentage of water. Furthermore, bioethanol from SSF method showed peaks corresponding to CH, CH3, and CO functional groups. It can be concluded that SSF method give bioethanol with optimum result.

Installing xylose assimilation and cellodextrin phosphorolysis pathways in obese Yarrowia lipolytica facilitates cost-effective lipid production from lignocellulosic hydrolysates

BackgroundYarrowia lipolytica, one of the most charming chassis cells in synthetic biology, is unable to use xylose and cellodextrins.ResultsHerein, we present work to tackle for the first time the engineering of Y. lipolytica to produce lipids from cellodextrins and xylose by employing rational and combinatorial strategies. This includes constructing a cellodextrin-phosphorolytic Y. lipolytica by overexpressing Neurospora crassa cellodextrin transporter, Clostridium thermocellum cellobiose/cellodextrin phosphorylase and Saccharomyces cerevisiae phosphoglucomutase. The effect of glucose repression on xylose consumption was relieved by installing a xylose uptake facilitator combined with enhanced PPP pathway and increased cytoplasmic NADPH supply. Further enhancing lipid production and interrupting its consumption conferred the obese phenotype to the engineered yeast. The strain is able to co-ferment glucose, xylose and cellodextrins efficiently, achieving a similar μmax of 0.19 h−1, a qs of 0.34 g-s/g-DCW/h and a YX/S of 0.54 DCW-g/g-s on these substrates, and an accumulation of up to 40% of lipids on the sugar mixture and on wheat straw hydrolysate.ConclusionsTherefore, engineering Y. lipolytica capable of assimilating xylose and cellodextrins is a vital step towards a simultaneous saccharification and fermentation (SSF) process of LC biomass, allowing improved substrate conversion rate and reduced production cost due to low demand of external glucosidase.

Maximizing Bioethanol Production from Eucalyptus globulus Using Steam Explosion Pretreatment: A Multifactorial Design and Fermenter Development for High Solid Loads

Steam explosion pretreatment is suitable for bioethanol production from Eucalyptus globulus wood. Multifactorial experiment designs were used to find the optimal temperature and residence time required to obtain the best glucose yield from the enzymatic hydrolysis of pretreated materials. The chemical composition, crystallinity index, morphology and polymerization degree of the pretreated materials were correlated with enzymatic accessibility. Simultaneous saccharification and fermentation (SSF) using a fed-batch strategy was applied to three different laboratory-scale fermenters. The optimization of the pretreatment was obtained at 208 °C and 11 min. However, the enzymatic hydrolysis performance did not show significant differences from the material obtained at 196 °C and 9.5 min, which was determined to be the real optimum, owing to its lower energy requirement. The vertical fermenter with type “G” blades and the horizontal fermenter with helical blades were both highly efficient for reaching ethanol yields close to 90% based on dry wood, and ethanol concentrations close to 9.0% v/v.

Novel cyclic shifting of temperature strategy for simultaneous saccharification and fermentation for lignocellulosic bioethanol production

In the current study, a novel strategy using cyclic shifting of temperature was developed for simultaneous saccharification and fermentation (SSF) for bioethanol production from rice straw. The in-situ cellulase production, saccharification and fermentation was carried out using P. janthinellum and S. cerevisiae. Bioethanol titer of 14.98 g/l was obtained using base followed by acid pretreated rice straw by employing the cyclic shifting of temperature strategy “30 °C for 2 h to 40 °C for 2 h”. The holding time was further tuned to increase the productivity and the tuned condition 30 °C(1.7 h) – 40 °C(2 h) improved the bioethanol titer to 15.9 g/l. Using this strategy, resulted 5.1-fold and 2.8-fold increment of bioethanol production compared to known approaches, SSF at mutual optimum temperature and prolong prehydrolysis followed by fermentation respectively. The application of cyclic shifting of temperature strategy can unleash a great potential in enhancing the yield and efficiency for a sustainable lignocellulosic bioethanol production.

Bacterial Nanocellulose‐Based Composite Biocatalysts for Starch‐to‐Bioethanol Valorization under Simultaneous Saccharification and Fermentation

AbstractComposite biocatalysts (CB) consisting of amylases and Saccharomyces cerevisiae immobilized separately on bacterial nanocellulose (BNC) are used for the process of simultaneous saccharification and fermentation (SSF) of starch (5%, w/v) for bioethanol production. Parameters such as: i) addition of phosphates and/or divalent metal‐ions salts during the co‐immobilization process of the amylases, ii) required co‐immobilization time, iii) fermentation temperature and initial pH of starch, and iv) CB as single or double freeze‐dried are studied. The utilization of double freeze‐dried CB exhibits fermentation efficiency 89.9% and ethanol yield 0.51 g ethanol g−1 starch while the single freeze‐dried CB 81.1% and 0.46 g ethanol g−1 starch, respectively. In the case of double freeze‐dried CB, the fermentation efficiency decreases by only 27.1% in two‐recycling batches, while in the single freeze‐dried one decreases by 51.3%. The application of double freeze‐dried CB can be used for: i) the eco‐friendly biosynthesis of value‐added bioproducts; ii) the promising option for fuel‐grade bioethanol through starchy wastes or foodstuff starchy residues treatment, and iii) the implementation of industrialization. Finally, to simulate an industrial process of one‐step SSF of starch by applying a CB model, a technoeconomic analysis is evaluated, where using BNCs makes the bioprocess cost‐effective and environmentally favorable, simultaneously.

Utilization of pretreated oil palm empty fruit bunches and their hydrolysate for ethanol production by Indonesian ethanologenic yeast

Abstract. Anita SH, Oktaviani M, Hermiati E. 2023. Utilization of pretreated oil palm empty fruit bunches and their hydrolysate for ethanol production by Indonesian ethanologenic yeast. Biodiversitas 24: 5243-5252. Oil Palm Empty Fruit Bunches (OPEFB) represent a polysaccharide-rich raw material with promising potential for ethanol production. This study aimed to investigate the ethanologenic yeasts, specifically Saccharomyces cerevisiae InaCC Y93 and Kluyveromyces marxianus InaCC Y119, affect bioethanol production in three different systems: Separate Hydrolysis and Fermentation (SHF), Simultaneous Saccharification and Fermentation (SSF), and Prehydrolysis-Simultaneous Saccharification and Fermentation (PSSF). This work is distinguished by the use of indigenous Indonesian yeast strains, including a thermotolerant strain. In the pretreatment process, 1.13% oxalic acid was added to OPEFB and subjected to microwave treatment at 190°C for 3.01 min. Subsequently, cellulase enzymes (40 FPU/g) and a 10% (w/v) yeast inoculum were introduced into 5.27 g dry weight of pretreated OPEFB pulp. The OPEFB acid hydrolysate was also subjected to fermentation. Ethanol content was monitored at 24 h intervals for 72 h. The PSSF system employs K. marxianus InaCC Y119 at 48 h exhibited the highest ethanol concentration, yielding 0.290 g/g, equivalent to approximately 51.20% of the theoretical yield. Additionally, K. marxianus InaCC Y119 demonstrated its capability to ferment the OPEFB acid hydrolysate into ethanol. These findings underscore the considerable potential of K. marxianus for applications in fermenting both hexose and pentose sugars to produce ethanol within higher-temperature systems.

Monitoring of simultaneous saccharification and fermentation of ethanol by multi-source data deep fusion strategy based on near-infrared spectra and electronic nose signals

Fuel ethanol represents a future energy trajectory, and the simultaneous saccharification and fermentation (SSF) technique emerges as the principal approach for ethanol production. This scholarly inquiry offers an innovative means to monitor the SSF process for ethanol meticulously. Employing a profound fusion strategy that effectively amalgamates diverse data sources. The convolutional neural network and recurrent neural network (RNN) architectures are thoughtfully crafted and designed to enable autonomous feature self-learning from near-infrared spectra and electronic nose data. These intricately devised networks further implement data fusion strategies at the granular level of features. Ultimately, a deep fusion correction model was devised and rigorously validated using two distinct data sources, namely near-infrared spectroscopy and electronic nose data. The obtained results demonstrate a discernible improvement in the overall predictive accuracy of the model when employing the fusion feature strategy, surpassing the model constructed solely on a single technical data source. Regarding the monitoring of ethanol content, the optimal RNN fusion model exhibited remarkable performance metrics, with a root mean square error of prediction (RMSEP) value of 3.2265, a coefficient of determination (R2) value of 0.9880, and a relative percent deviation (RPD) value of 9.2662. In terms of monitoring glucose content, the optimal RNN fusion model also demonstrated commendable performance, with the following respective parameters: RMSEP was 3.2770, R2 was 0.9840, and RPD was 8.0085. The overall results indicate that the multi-sensor data fusion strategy not only improves the performance of the model but also provides valuable insights into the fermentation process.

Fed-batch SSF with pre-saccharification as a strategy to reduce enzyme dosage in cellulosic ethanol production

The pulp and paper industry is a strategic sector to be converted into a forest-based biorefinery, taking advantage of know-how, existing infrastructures and well-established logistic operations to deal with a daily high volume of forest residues. Bioethanol production from Eucalyptus globulus bark previously pretreated by kraft pulping was assessed following two configurations at the bioreactor scale: separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF). This last configuration was optimized by using a pre-saccharification and a fed-batch feeding (FB PS-SSF), allowing for a reduction in the enzyme dosage from 25 to 10 FPU gCH−1, which is very advantageous from an economic point of view. For 10 FPU gCH−1 enzyme dosage and 20 % (w/v) total solids loading, an ethanol concentration of around 70.6 g L−1 was accomplished, corresponding to overall conversion efficiency and productivity of about 78 % and 1.35 g L−1 h−1, respectively. Increasing solids loading from 20 to 26 % (w/v), using the same enzyme dosage, resulted in the highest ethanol concentration (84.6 g L−1) despite the too-long assay and the decline in productivity. Overall, FB PS-SSF improved bioethanol concentration and allowed decreased enzymatic usage over SHF, maintaining high ethanol concentration.

Development of an ultrasound-assisted pre-treatment strategy for the extraction of d-Limonene toward the production of bioethanol from citrus peel waste (CPW)

Citrus is one of the world’s most abundant fruits containing vitamins, pigments, and fragrances, making it vital for several industries. However, these fruits contain about 45–50% residues (peels), which often end up as waste and can be harmful to the environment if not properly treated. Bioethanol production from citrus peel waste offers a potential solution to this problem. Hence, this study explores the potential of using ultrasound-assisted pre-treatment method as a novel strategy to extract d-Limonene (essential oil in the residue), and further demonstrates bioethanol production. This was done by investigating ultrasonication’s optimal effect on pre-treatment of the citrus residue, followed by bioethanol production. The results show that, optimum values for d-Limonene extraction were obtained at a temperature of 14.6 °C and an ultrasound intensity of 25.81 W/cm2 with a validation yield of 134 ± 4.24 mg/100 g dry CPW. With optimal ultrasonic parameters, the study went further to demonstrate the effect of the essential oil on bioethanol production which is hindered by the oils present. Key findings show better bioethanol yield once the essential oil was extracted (treated) from the citrus waste as opposed to it not extracted (untreated), with a 66 and a 29% increase when comparing simultaneous saccharification and fermentation (SSF) and sequential hydrolysis and fermentation (SHF) respectively. Based on this result, ultrasound-assisted extraction as a pretreatment method was found suitable for bioethanol production from citrus residue and could be utilized as a biorefinery pre-treatment approach to scale bioethanol production.

Comparative Analysis of Cellulosic Ethanol Production from Lignocellulosic Substrate Moringa oleifera Using Kluyveromyces marxianus and Zymomonas mobilis

In the current investigation, the woody stem of Moringa oleifera was processed by chipping and milling and was subsequently exposed to a combination of pretreatments involving a 3% v/v solution of nitric acid and autohydrolysis. The simultaneous saccharification and fermentation (SSF) of the pretreated hydrolysate of M. oleifera was conducted using Zymomonas mobilis and Kluyveromyces marxianus in occurrence of commercial cellulase enzyme, Tween 80, and sodium azide. The fermentation process parameters for Z. mobilis were optimized individually, including a substrate concentration of 5% (w/v), concentration of inoculum 5% (v/v), pH 5.4, and temperature 34 °C. Similarly, for K. marxianus, the process parameters were optimized individually, with a substrate concentration of 5% (w/v), an inoculum concentration of 3% (v/v), a pH of 5.1, and a temperature of 41 °C. The highest cellulosic ethanol concentration was achieved by the micro-organism K. marxianus after a fermentation period of 96 h.

Overcoming extended lag phase on optically pure lactic acid production from pretreated softwood solids.

Optically pure lactic acid (LA) is needed in PLA (poly-lactic acid) production to build a crystalline structure with a higher melting point of the biopolymer than that of the racemic mixture. Lignocellulosic biomass can be used as raw material for LA production, in a non-food biorefinery concept. In the present study, genetically engineered P. acidilactici ZP26 was cultivated in a simultaneous saccharification and fermentation (SSF) process using steam pretreated softwood solids as a carbon source to produce optically pure D-LA. Given the low concentrations of identifiable inhibitory compounds from sugar and lignin degradation, the fermentation rate was expected to follow the rate of enzymatic hydrolysis. However, added pretreated solids (7% on weight (w/w) of water-insoluble solids [WIS]) significantly and immediately affected the process performance, which resulted in a long lag phase (more than 40h) before the onset of the exponential phase of the fermentation. This unexpected delay was also observed without the addition of enzymes in the SSF and in a model fermentation with glucose and pretreated solids without added enzymes. Experiments showed that it was possible to overcome the extended lag phase in the presence of pretreated softwood solids by allowing the microorganism to initiate its exponential phase in synthetic medium, and subsequently adding the softwood solids and enzymatic blend to proceed to an SSF with D-LA production.

Simultaneous saccharification and butanediol production from unpretreated lignocellulosic biomass using an enzymatic cocktail of a newly constructed bacterial consortium

Bioconversion lignocellulosic biomass (LCB) to 2,3-butanediol (2,3-BDO) is a sustainable and energy-intensive practice, but its economic feasibility has been hindered by costly pretreatment and the cumbersome fermentation process. Herein, the hindgut metagenome of Cyrtotrachelus buqueti is assembled and sequenced to construct bacterial consortia for efficient LCB degradation. One of these consortia, named artificial synthetic bacteria community II (ASCII), is effective in degrading unpretreated LCB, achieving degradation rates of 85.33% for cellulose, 77.43% for hemicellulose, and 57.63% for lignin. The secretory protein extracted from ASCII is used for simultaneous saccharification and fermentation (SSF) from unpretreated LCB. Furthermore, fed-batch SSF resulted in 40.62 g/L of 2,3-BDO with a productivity of 0.42 g/L/h reached by Klebsiella sp. CQHG35. This study provides a new approach for the construction of bacterial consortia and their use in SSF for the production of 2,3-BDO from unpretreated LCB, representing a significant breakthrough in this field.