Initial Sugar Research Articles

Analysis and design of low gas emission of ethanol fuel from ionic liquid-assisted pretreatment of biomass

The growth of gas emissions (GE) in the environment that stirred climate change, has correlated with the decline of fossil fuels. Generally, GE was produced by burning fossil fuels such as gasoline in the combustion engine. Gasoline has higher air toxic emissions than ethanol. Hence, the investigation of ethanol has gained attention. On the other hand, biomass has become a renewable source of ethanol. However, due to the rigid structure of biomass, biomass pretreatment is needed before the hydrolysis and fermentation process. Recently, growing attention has been devoted to applying ionic liquids (ILs)-assisted pretreatment despite the high-cost process. Therefore, in this study, to optimize the ethanol production from biomass, the simulation using SuperPro Designer (SPD) software was conducted. Bagasse as biomass material was treated by IL, namely choline acetate (ChOAc), with the range of ratio IL/biomass of 0–1.5. The developed SPD model was validated with published data. The results indicated that the minimum ratio of IL/biomass was 1.3. When in the hydrolysis performed at high-loading after 72 h reaction time, the glucose and xylose concentrations were 49 g/L and 13 g/L, respectively. When the fermentation process was conducted, the initial mixed sugar solution concentration was 23 g/L of glucose and 6 g/L of xylose. Then, the ethanol concentration was 15 g/L at 24 h, which was 89% of the theoretical ethanol yield. To conclude, the developed SPD model not only could support to optimize the biomass refinery into low GE of ethanol but also could reduce large cost experimental.

Improvements in the formulation of sugarcane-sweet sorghum juices fermentation media for enhanced isopropanol and butanol production

The production of isopropanol and butanol (IB) has been gaining attention through isopropanol-butanol-ethanol (IBE) fermentation. In this work, the substrate inhibition and butanol tolerance of Clostridium beijerinckii DSM 6423 in isopropanol-butanol (IB) production by isopropanol-butanol-ethanol (IBE) fermentation from an industrial mixture of sugarcane and sweet sorghum juices were assessed. The results showed that an initial sugar concentration of 40 g/L in the industrial juices showed the best kinetic for the fermentation. The formulation of a low-cost medium for IB production from industrial juices by C. beijerinckii DSM 6423 was also studied. Corn steep liquor (CSL), a byproduct of the wet milling of corn, could serve as a nutrient of low cost and replace both yeast extract and vitamin complex without significantly affecting the production of butanol and isopropanol. A CSL concentration of 5 g/L was shown to be adequate to achieve the best results. C. beijerinckii DSM 6423 produced 5.3 and 7.9 g/L of isopropanol and butanol, respectively, with a sugar conversion of 93%. This work provides valuable insights into cost-effective nutritional supplementation of industrial juices for IB production.

Cost-effective valorization of cassava fibrous waste into enantiomerically pure D-lactic acid: Process engineering and kinetic modelling approach

Cassava fibrous waste (CFW) valorization on the synthesis of D (-) lactic acid (DLA) holds enormous importance, particularly in the production of thermostable and biodegradable polymers. In this study, microbial kinetic modelling was carried out to investigate the dynamics of cassava fibrous waste enzyme hydrolysate (CFWEH) utilization towards DLA production. Designed biomass approach was attempted to evaluate the natural DLA producing organisms, capable of metabolizing CFWEH into optically pure DLA. Sporolactobacillus inulinus (NBRC 13595) was found to be the elite strain, resulting the yield of 99.43 % optically pure DLA using CFWEH-supplemented medium. Yeast extract (2 gL −1 ) was observed to be potential nitrogen source over other complex nitrogen sources for kinetic modelling investigation. Kinetic parameters predicted from the proposed model for DLA production showed maximum specific growth rate, μ max - 0.36 (h −1 ); growth-associated product coefficient ( α = 0 . 47 gg −1 ) and specific productivity ( q P , m a x = 1 . 12 gg −1 h −1 ) respectively. Experimental data of biomass growth, substrate consumption and DLA production with initial sugar concentrations ranging from 20–180 gL −1 was found to be synchronized well with the simulated dynamic profiles. Kinetic investigation reported in this study is a novice attempt enumerating the valorization potential of CFW for the synthesis of value-added products including DLA at commercial scale in near future. • High optical purity (99.43 %) was achieved for D-Lactic Acid. • Valorization potential of cassava fibrous waste was elucidated. • First kind of study on kinetic modelling, utilizing cassava fibrous waste. • Potential scope for techno-economic feasibility of cassava fibrous waste.

Optimization of fermentation conditions for fermented green jujube wine and its quality analysis during winemaking.

The objective was to study the optimization of fermentation conditions for fermented green jujube wine and quality analysis. This study investigated the fermentation process conditions, the changes in physicochemical indexes, antioxidant capacity and volatile compounds measured from green jujube wine during winemaking. The optimized conditions (the initial sugar, yeast addition, fermentation time and SO2 treatments) for green jujube wine were 24%, 0.3%, 8d, 80mg/L, respectively. The results showed that the variation trend of different substances in green jujube wine in different fermentation periods were different. In the process of alcohol fermentation, the green jujube wine had a high 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability, 2,2'-amino-di (2-ethyl-benzothiazoline sulphonic acid-6) ammonium salt (ABTS) free radical scavenging ability and reducing power. Furthermore, a total of 50 volatile compounds were identified in green jujube wine, in which the relative content of aldehydes, ketones, heterocyclic and aromatic compounds were significantly reduced after fermentation.

Co-culture of Saccharomyces cerevisiae (VS3) and Pichia stipitis (NCIM 3498) enhances bioethanol yield from concentrated Prosopis juliflora hydrolysate.

Biphasic acid hydrolysates and enzymatic hydrolysates from carbohydrate-rich Prosopis juliflora, an invasive perennial deciduous shrub of semi-arid regions, were used for bioethanol production. Saccharomyces cerevisiae and Pichia stipitis were used for fermentation of hexoses and pentoses. P. juliflora acid hydrolysate with an initial sugar concentration of 18.70 ± 0.16g/L was concentrated to 33.59 ± 0.52g/L by vacuum distillation. The concentrated hydrolysate was pretreated and fermented by mono- and co-culture methods either singly or in combination with enzyme hydrolysate and ethanol yields were compared. Monoculture with S. cerevisiae (VS3) and S. cerevisiae (NCIM3455) yielded maximum ethanol of 36.6 ± 1.83g/L and 37.1 ± 1.86g/L with a fermentation efficiency of 83.94 ± 4.20% and 84.20 ± 4.21%, respectively, after 36h of fermentation. The ethanol yield obtained was 0.428 ± 0.02g/g substrate and 0.429 ± 0.02g/g substrate with a productivity of 1.017 ± 0.051g/L/hand 1.031 ± 0.052g/L/h, respectively. P. stipitis (NCIM3498) yielded maximum ethanol of 24g/L with ethanol yield of 0.455 ± 0.02g/g substrate and a productivity of 1.004 ± 0.050g/L/h after 24h of fermentation. With concentrated acid hydrolysate as substrate, S. cerevisiae (VS3) produced ethanol of 8.52 ± 0.43g/L, whereas S. cerevisiae (NCIM3455) produced 5.96 ± 0.30g/L of ethanol. P.stipitis (NCIM3498) produced 4.52 ± 0.23g/L of ethanol by utilizing 14.66 ± 0.87g/L of sugars. Co-culture with S. cerevisiae (VS3) addition after 18h of addition of P. stipitis (NCIM3498) to the mixture of concentrated acid hydrolysate and enzyme hydrolysate produced 13.86 ± 0.47g/L of ethanol with fermentation efficiency, ethanol yield and productivity of 87.54 ± 0.54%, 0.446 ± 2.36g/g substrate and 0.385 ± 0.014g/L/h, respectively. Hence, it is concluded that co-culture with S. cerevisiae and P. stipitis is feasible, further scaling up of fermentation of P. juliflora substrate for bioethanol production.

Subsequent improvement of lactic acid production from beet molasses by Enterococcus hirae ds10 using different fermentation strategies

Different fermentation strategies were investigated for improving lactic acid (LA) production by homofermentative LA-producing strain, Enterococcus hirae ds10. Batch mode with initial sugar molasses of 69.53 g/L achieved LA production of 36.79 g/L with a yield of 0.91 g/g and productivity of 1.02 g/L/h; however, 52% of sugar molasses was only consumed. Otherwise, in batch mode with high cell density (HCD), strain ds10 consumed more substrate achieving LA production at 49.49 g/L at yield (0.91 g/g) and low LA productivity (0.41 g/L/h). Subsequently, one-pulse and multi-pulse fed-batch strategies with/without HCD were provided better sugar utilization and higher LA production but low LA productivity was obtained. Interestingly, the repeated batch fermentation was conducted for 16 runs and achieved the highest LA of 61.76 g/L after 30 h at a higher initial sugar concentration of 85.87 g/L with an improvement of LA productivity at 2.06 g/L/h and yield at 0. 97 g/g.

Conversion of sugar beet residues into lipids by Lipomyces starkeyi for biodiesel production

BackgroundLipids from oleaginous yeasts emerged as a sustainable alternative to vegetable oils and animal fat to produce biodiesel, the biodegradable and environmentally friendly counterpart of petro-diesel fuel. To develop economically viable microbial processes, the use of residual feedstocks as growth and production substrates is required.ResultsIn this work we investigated sugar beet pulp (SBP) and molasses, the main residues of sugar beet processing, as sustainable substrates for the growth and lipid accumulation by the oleaginous yeast Lipomyces starkeyi. We observed that in hydrolysed SBP the yeast cultures reached a limited biomass, cellular lipid content, lipid production and yield (2.5 g/L, 19.2%, 0.5 g/L and 0.08 g/g, respectively). To increase the initial sugar availability, cells were grown in SBP blended with molasses. Under batch cultivation, the cellular lipid content was more than doubled (47.2%) in the presence of 6% molasses. Under pulsed-feeding cultivation, final biomass, cellular lipid content, lipid production and lipid yield were further improved, reaching respectively 20.5 g/L, 49.2%, 9.7 g/L and 0.178 g/g. Finally, we observed that SBP can be used instead of ammonium sulphate to fulfil yeasts nitrogen requirement in molasses-based media for microbial oil production.ConclusionsThis study demonstrates for the first time that SBP and molasses can be blended to create a feedstock for the sustainable production of lipids by L. starkeyi. The data obtained pave the way to further improve lipid production by designing a fed-batch process in bioreactor.Graphical abstract

Efficient biorefinery process for lactic acid production from date wastes with alleviating substrate inhibition effect using thermo-alkaline repeated batch fermentation

In the current work, date wastes were used for lactic acid (LA) production under thermo-alkaline conditions to overcome some fermentation challenges. Amongst 27 bacterial isolates that produced LA from date juice, isolate D-218 exhibited better growth stability and LA production under various stressed conditions. This isolate was characterized as Bacillus coagulans D-218 using physiological and molecular identification methods. In batch fermentation mode, strain D-218 could not completely utilize 80 g/L of the total sugar and produced only 45.8 ± 2.8 g/L of LA at LA productivity of 0.214 g/L.h and high residual sugar (29.2 g/L) was unutilized in the fermentation media. Different repeated batch fermentations with different initial sugar concentrations and gradual increase in sugar concentrtions were conducted to maximize LA productivity. Starting with 60 g/L of total sugar, four runs of repeated batch fermentations were conducted that enhanced the LA productivity (70%) to 0.49 g/L.h. Another 9 runs were initiated with 40 g/L which further improved LA productivity that reached up to 0.77 g/L.h. Surprisingly, initiating fermentations with 20 g/L of total sugar successfully attained long-term fermentation (18 runs) with high LA yield and productivity without carbon loss of initiated startup sugar of date waste. In this process, strain D-218 could completely consume 80 g/L sugars with high LA production titer (72.9 ± 0.56 g/L), yield (0.92 g/g), and productivity (0.71 g/L.h). This study is the first to exploit date waste in a cost-effective system for high-titer lactic acid production under thermo-alkaline conditions (pH 9.0; 50 °C) and to report repeated batch fermentation for LA production from date wastes.

Enhanced Cadaverine Production by Engineered Escherichia coli Using Soybean Residue Hydrolysate (SRH) as a Sole Nitrogen Source.

An economical source of nitrogen is one of the major limiting factors for sustainable cadaverine production. The utilization potential of soybean residue for enhanced cadaverine production by engineered Escherichia coli DFC1001 was investigated in this study. The SRH from soybean residue could get the protein extraction rate (PE) of 67.51% and the degree of protein hydrolysis (DH) of 22.49%. The protein molecular weights in SRH were mainly distributed in 565Da (72.28%) and 1252Da (17.11%). These proteins with small molecular weights and concentrated molecular weight distribution were favorable to be transformed by engineered E. coli DFC1001, and then SRH replaced completely yeast powder as an only nitrogen source for cadaverine production. The maximum cadaverine productivity was 0.52g/L/h, achieved with a constant speed feeding strategy in the optimized SRH fermentation medium containing an initial total sugar concentration of 30g/L and exogenous added minerals, which indicated that soybean residue could be a potential feedstock for economic cadaverine production.

METFORMIN ASSOCIATED LACTIC ACIDOSIS

SESSION TITLE: Medical Student/Resident Critical Care Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Metformin is the most commonly used oral hypoglycemic agent to treat Type 2 Diabetes Mellitus owing to its favorable safety profile. Although metformin is renally cleared, drug levels generally remain within the therapeutic range and lactate concentrations are not substantially increased when used in patients with mild to moderate chronic kidney disease. However, the situation is different when a patient has acute renal insufficiency with progressively worsening kidney function. Here, we present a case of severe Metformin-associated lactic acidosis. CASE PRESENTATION: A 66-year-old Hispanic man with type-2 diabetes on metformin, hypertension, coronary artery disease and chronic back pain presented to our hospital with 2 days of altered mental status and worsening back pain. Initial physical examination was unremarkable except for tachycardia with a heart rate of 156. In the emergency department, laboratory abnormalities included initial blood sugar of 62, creatinine of 11, anion gap of 41 and lactate of 18, bicarbonate of 6 and pH of 6.7 on arterial blood gas. The patient worsened after transfer to critical care unit with acute development of hypoxia and hypotension and had to be intubated and started on mechanical ventilation and vasopressors. Differential diagnosis at this point was broad and it was thought that hypotension, acidemia, and severe metabolic derangement could be consistent with septic shock vs metformin-associated lactic acidosis. Patient was started on broad spectrum antibiotics and a nephrology consult was obtained and the patient was dialyzed within few hours after the placement of temporary dialysis catheter. Patient's pH improved to 7.2 after 1 session of dialysis and vasopressors requirement went down as well. The patient was extubated on day 4 and renal function improved over the coming days as well. DISCUSSION: The overall incidence of lactic acidosis in metformin users is generally low and varies across studies from approximately 3-10 per 100,000 person-years [1]. The overall mortality rate of Metformin associated lactic acidosis is 25.4% according to the study by Renda et al. [2]. Mortality is associated with the extent of acidosis while acute renal failure is associated with a low mortality. It is crucial to maintain a high suspicion of this complication in the differential diagnosis at the earliest stage for patients with metabolic acidosis and history of metformin use. CONCLUSIONS: Lactic acidosis resulting from metformin toxicity should be suspected in any patient who has all of the following five criteria: (1) a history of metformin use; (2) a markedly elevated lactate level (> 15 mmol/L) with a large anion gap (> 20); (3) severe acidemia (pH 7.1); (4) a very low serum bicarbonate level (< 10 mmol/L); and (5) a history of renal insufficiency. Education of both patients and providers to avoid metformin when there is a risk of renal failure is crucial. Reference #1: https://jamanetwork.com/journals/jama/article-abstract/2084896 Reference #2: https://www.ncbi.nlm.nih.gov/pubmed/23436666/ DISCLOSURES: No relevant relationships by Anam Hassan, source=Web Response No relevant relationships by Muhammad Hasham Sarwar, source=Web Response

Operational considerations for hot-washing in potato crisp manufacture

As part of an overall programme aimed at reducing the acrylamide content of crisps, this paper explores the impact of hot-washing on potato slice sugar concentration during industrial scale manufacture. We investigated cold-washing as an alternative to hot-washing, hot-wash residence time and temperature to optimise sugar removal and therefore reduce the potential for high acrylamide levels after frying. Due to the variable nature of potatoes, an extensive variability study was performed to determine confidence boundaries of results. It was found that the cold-wash unit removed on average 21% of the initial sugar content. In the hot-wash the current operational residence time of 3.5 min at 70 °C gave a sugar reduction of 27.5%, which could be increased to 48.5% if residence time is extended to 5 min. Hot-wash temperatures of 40 °C–60 °C were found to increase glucose and fructose content and therefore the potential for acrylamide formation. A “double cold-wash” was trialled and proved to be as successful as hot-washing at 70 °C for all but the highest sugar potatoes, challenging the current operational process and offering the potential for major energy savings.

Inoculum Size and Age Studies on Single and Mixed Strain Fermentation of Grape Juice

Single and mixed strain fermentation were compared to check the effect on properties of wine. Two strains of Saccharomyces cerevisiae (MTCC 11815 &amp; MTCC 170) were used to study the effect of inoculum age and inoculum size on fermentation of grape juice. The inoculum sizes used were 2%, 5%, 10% and 15%, while inoculum age effect was studied using 24 h, 48 h and 60 h old inoculum. Fermentation efficiency of 77.2% was achieved in mixed strain culture using 15% inoculum, 17% initial sugars giving ethanol concentration of 6.70% (w/v) after 48 hrs. Fermentation efficiency of 84.65% was achieved with MTCC170 using 15% inoculum and 17% initial sugars giving ethanol concentration of 7.34% (w/v) in 48 hrs. Strain MTCC11815 produced 8.5% (w/v) ethanol from 17% initial sugars giving 98% efficiency using 2 and 5% inoculum. Concentration of phenolics increased with inoculum concentration while nitrogen and phosphates did not show any regular trend. The nitrogen and phosphate concentration was affected by type of strain rather than other factors.

Managing self-heating & quality changes in forest residue wood waste piles

As renewable energy initiatives intensify, the benefits of optimizing recycled wood waste and forestry residues for bioenergy generation are clear. Self-heating fires and degradation during outdoor pile storage however continue to result in safety risks and economic losses. Furthermore, the storage dynamics of older wood waste material remain understudied. The following presents the longest continuous North American forestry residue storage trial, comparing the storage characteristics of woodchip piles built with fresh and aged material (previously stored for 20 months). Temperature sensors were placed within industrial woodchip piles (consisting primarily of poplar) at Pineland Nurseries (Manitoba, Canada). Monitoring occurred for 459 days (August 2017–November 2018) where samples were periodically characterized for dry-matter loss, pH, bulk density, particle size, moisture, ash and free sugar content. Significantly higher temperatures were sustained in the aged pile throughout the storage trial compared to the fresh pile where temperatures decreased within a month after an initial thermal spike. Decreased particle size and higher moisture content in the aged material appeared to have the most impact on thermal retention. Microorganism reintegration theory supported our findings where initial sugar content did not correlate with higher initial self-heating in the aged pile. This study highlights several critical considerations for forestry residue pile management.

Continuous Ethanol Production from Molasses via Immobilized Saccharomyces cerevisiae on Different Carriers on Pilot Scale

IMMOBILIZATION of yeast cells for continuous ethanol production has been extensively studied worldwide during the past few years because it showed significant advantages compared to the production by free cell system. Using renewable substrates such as Egyptian cane and beet molasses becomes necessary to reduce food crops for bioethanol production. This study investigates the immobilization of commercial strain of Saccharomyces cerevisiae on different carriers (sugarcane bagasse, rice straw, wheat straw, and Na-alginate) for continuous ethanol production on a pilot scale. The results demonstrated that sugarcane bagasse was the best carrier for yeast cell immobilization. This substrate produced 66.30g/ L ethanol, 2.76g/ L/ hr as ethanol productivity, and 81% fermentation efficiency from the theoretical value, using a mixture of Egyptian cane and beet molasses with 16% initial sugar at 30°C and pH 4.5. Also, the production process is retained until 18 days continuously. From this study, it was clear that lignocellulosic materials provide suitable, cheap, and renewable carriers for immobilization of yeast cells used in the continuous ethanol production process.

Saccharification and fermentation of pretreated banana leaf waste for ethanol production

The present work reveals the potential applicability of banana leaf waste as feedstock for bioethanol production as very less work has been reported on this feedstock. For achieving the same, the performance of crude cellulases of Aspergillus niger JD-11 is explored for saccharification of untreated and pretreated (alkaline, dilute acid and steam) banana leaf waste. Therefore, to determine the best saccharifying conditions, the effects of various parameters such as enzyme loading (5–15 FPU/g), temperature (40–50 °C), surfactant addition (0.05–0.15% Tween 80 and PEG 6000) and substrate concentrations (2–6%) were studied at 150 rpm and pH 5.0. The crude cellulases yielded maximum reducing sugars (524.83 mg/g) from the dilute acid pretreated banana leaf waste at 45 °C, 15 FPU/g enzyme loading and 2% substrate loading in the presence of 0.15% PEG 6000 (w/v) as surfactant. The fermentation of enzymatic hydrolysate was carried out using initial reducing sugars concentration of 40 g/L in the medium at pH 5.5, 150 rpm and 30 °C for 30 h with the help of Saccharomyces cerevisiae. Ethanol production was estimated at every 6 h and maximum ethanol yield of 0.38 g/g sugar and productivity of 1.28 g/L/h was obtained after 12 h of fermentation of banana leaf waste hydrolysate. Thus, the easily obtained banana leaf waste could be a promising feedstock for bioethanol production.

Sugar Transporter ZjSWEET2.2 Mediates Sugar Loading in Leaves of Ziziphus jujuba Mill.

In plants, sugar transporters play an important role in the allocation of sugars from cells in source organs to cells in sink organs. Hence, an understanding of the molecular basis and regulation of assimilate partitioning by sugar transporters is essential. Leaves are the main source of photosynthetic products. In jujube (Ziziphus jujuba Mill.), the mechanisms regulating initial sugar unloading in leaves are still unclear. In this study, an expression profiling analysis showed that ZjSWEET2.2, encoding a sugar transporter in the SWEET family, is highly expressed in leaves. Over-expression of ZjSWEET2.2 increased carbon fixation in photosynthetic organs. Our analyses showed that ZjSWEET2.2 encodes a plasma membrane-localized sugar transporter protein. Its expression levels were found to be suppressed under drought stress and by high concentrations of exogenous sugars, but increased by low concentrations of exogenous sugars. Finally, DNA sequence analyses revealed several cis-elements related to sugar signaling in the promoter of ZjSWEET2.2. Together, these results suggest that ZjSWEET2.2 functions to mediate photosynthesis by exporting sugars from photosynthetic cells in the leaves, and its gene expression is regulated by sugar signals.

Control of the galactose-to-glucose consumption ratio in co-fermentation using engineered Escherichia coli strains

Marine biomasses capable of fixing carbon dioxide have attracted attention as an alternative to fossil resources for fuel and chemical production. Although a simple co-fermentation of fermentable sugars, such as glucose and galactose, has been reported from marine biomass, no previous report has discussed the fine-control of the galactose-to-glucose consumption ratio in this context. Here, we sought to finely control the galactose-to-glucose consumption ratio in the co-fermentation of these sugars using engineered Escherichia coli strains. Toward this end, we constructed E. coli strains GR2, GR2P, and GR2PZ by knocking out galRS, galRS-pfkA, and galRS-pfkA-zwf, respectively, in parent strain W3110. We found that strains W3110, GR2, GR2P, and GR2PZ achieved 0.03, 0.09, 0.12, and 0.17 galactose-to-glucose consumption ratio (specific galactose consumption rate per specific glucose consumption rate), respectively, during co-fermentation. The ratio was further extended to 0.67 by integration of a brief process optimization for initial sugar ratio using GR2P strain. The strategy reported in this study will be helpful to expand our knowledge on the galactose utilization under glucose conditions.

Improvement in Ethanol Yield from Lignocellulo-Starch Biomass using Saccharomyces cerevisiae alone or its Co-culture with Scheffersomyces stipitis

Background:Literature on ethanol production from Lignocellulo-Starch Biomass (LCSB) containing starch besides cellulose and hemicellulose, is scanty. Fed-Batch Separate Hydrolysis And Fermentation (F-SHF) was earlier found more beneficial than Fed-Batch Simultaneous Saccharification and Fermentation (F-SSF).Objective:The study aimed at modification of the saccharification and fermentation strategies by including a prehydrolysis step prior to the SSF and compared the ethanol yields with co-culture fermentation using hexose-fermenting Saccharomyces cerevisiae and pentose-fermenting Scheffersomyces stipitis.Methods:Fed-batch hybrid-SSF and Fed-Batch Separate Hydrolysis and Co-culture Fermentation (F-SHCF) in improving ethanol yield from Steam (ST) or Dilute Sulfuric Acid (DSA) pretreated LCSBs (peels of root and vegetable crops) were studied.Results:There was a progressive build-up of ethanol during F-HSSF up to 72h and further production up to 120h was negligible, with no difference among pretreatments. Despite very high ethanol production in the initial 24h of fermentation by S.cerevisiae under F-SHCF, the further increase was negligible. A rapid hike in ethanol production was observed when S. stipitis was also supplemented because of xylose conversion to ethanol.Conclusion:While ST gave higher ethanol (296-323 ml/kg) than DSA under F-HSSF, the latter was advantageous under F-SHCF for certain residues. Prehydrolysis (24h; 50°C) enhanced initial sugar levels favouring fast fermentation and subsequent saccharification and fermentation occurred concurrently at 37°C for 120h, thus leading to energy saving and hence F-HSSF was advantageous. Owing to the low hemicellulose content in LCSBs, the relative advantage of co-culture fermentation over monoculture fermentation was not significant.

Lipid Production by Yeasts Growing on Commercial Xylose in Submerged Cultures with Process Water Being Partially Replaced by Olive Mill Wastewaters

Six yeast strains belonging to Rhodosporidium toruloides, Lipomyces starkeyi, Rhodotorula glutinis and Cryptococcus curvatus were shake-flask cultured on xylose (initial sugar—S0 = 70 ± 10 g/L) under nitrogen-limited conditions. C. curvatus ATCC 20509 and L. starkeyi DSM 70296 were further cultured in media where process waters were partially replaced by the phenol-containing olive mill wastewaters (OMWs). In flasks with S0 ≈ 100 g/L and OMWs added yielding to initial phenolic compounds concentration (PCC0) between 0.0 g/L (blank experiment) and 2.0 g/L, C. curvatus presented maximum total dry cell weight—TDCWmax ≈ 27 g/L, in all cases. The more the PCC0 increased, the fewer lipids were produced. In OMW-enriched media with PCC0 ≈ 1.2 g/L, TDCW = 20.9 g/L containing ≈ 40% w/w of lipids was recorded. In L. starkeyi cultures, when PCC0 ≈ 2.0 g/L, TDCW ≈ 25 g/L was synthesized, whereas lipids in TDCW = 24–28% w/w, similar to the experiments without OMWs, were recorded. Non-negligible dephenolization and species-dependent decolorization of the wastewater occurred. A batch-bioreactor trial by C. curvatus only with xylose (S0 ≈ 110 g/L) was performed and TDCW = 35.1 g/L (lipids in TDCW = 44.3% w/w) was produced. Yeast total lipids were composed of oleic and palmitic and to lesser extent linoleic and stearic acids. C. curvatus lipids were mainly composed of nonpolar fractions (i.e., triacylglycerols).

Metabolic Engineering and Adaptive Evolution of Clostridium beijerinckii To Increase Solvent Production from Corn Stover Hydrolysate.

The production of acetone-butanol-ethanol by solventogenic Clostridium using lignocellulosic biomass can be a potential alternative to petroleum-based butanol. However, previous studies on nondetoxified lignocellulose hydrolysate could not provide better results when compared to those in synthetic medium. In this study, we engineered the pentose pathway of Clostridium beijerinckii NCIMB 8052, which was then subjected to adaptive laboratory evolution in the gradient mixture of synthetic medium and pretreated corn stover enzymatic hydrolysate (CSH) prepared according to the National Renewable Energy Laboratory (NREL) standard. The final resultant strain CIBTS1274A produced 20.7 g/L of total solvents in NREL CSH diluted to 6% initial total sugars, supplemented with ammonium acetate. This performance was comparable with that of corn-based butanol. In addition, this strain was successfully used in the scale-up operation using nondetoxified corn stover and corncob hydrolysate at Lignicell Refining Biotechnologies Ltd., which once was the only commercial biobutanol industry in the world.