Dilute Acid Research Articles

Highly Efficient Production of Cellulosic Ethanol from Poplar Using an Optimal C6/C5 Co-Fermentation Strain of Saccharomyces cerevisiae.

Cellulosic ethanol is the key technology to alleviate the pressure of energy supply and climate change. However, the ethanol production process, which is close to industrial production and has a high saccharification rate and ethanol yield, still needs to be developed. This study demonstrates the effective conversion of poplar wood waste into fuel-grade ethanol. By employing a two-step pretreatment using sodium chlorite (SC)-dilute sulfuric acid (DSA), the raw material achieved a sugar conversion rate exceeding 85% of the theoretical value. Under optimized conditions, brewing yeast co-utilizing C6/C5 enabled a yield of 35 g/L ethanol from 10% solid loading delignified poplar hydrolysate. We increased the solid loading to enhance the final ethanol concentration and optimized both the hydrolysis and fermentation stages. With 20% solid loading delignified poplar hydrolysate, the final ethanol concentration reached 60 g/L, a 71.4% increase from the 10% solid loading. Our work incorporates the pretreatment, enzymatic hydrolysis, and fermentation stages to establish a simple, crude poplar waste fuel ethanol process, expanding the range of feedstocks for second-generation fuel ethanol production.

The Durability of Concrete Mortars with Different Mineral Additives Exposed to Sulfate Attack

For several years, extensive research investigations have been conducted examining the effects of acids commonly encountered by industrial facilities in manufacturing environments. Numerous studies have been conducted to examine the durability of concrete containing various chemical additives and fine metals when exposed to various acid solutions, as well as the preventive steps taken to avoid the deterioration of concrete associated with these acids. This research includes an examination of enhancing the effectiveness and function of concrete when exposed to sulfuric acid. It explores the use of waterproofing (WP) and complementary cementitious materials (SCMs), including silica fume Nano silica and fly ash, as well as a water-reducing additive. Cube-shaped samples measuring 100 x 100 x 100 mm were prepared and completely immersed in 2.5% dilute sulfuric acid solution for 90 and 180 days. . Compressive strength, tensile strength, and absorption tests were performed after 28 days, as well as after immersion in a 2.5% dilute acid solution for 90 and 180 days. The results revealed that after 90 days, there was a 31% reduction in compressive strength for mixtures with 25% FA and 5% SF, and a 46% decrease for mixtures containing WP, when compared to their corresponding results at the 28 day age under standard conditions. Mineral admixtures significantly reduce absorption rates. After 90 days, WP had 3% absorption during acid exposure, and after 180 days, the 25% FA and 5% SF mixture had 2.3% absorption. This results from reduced permeable voids due to decreased capillary pores, enhancing concrete durability. The findings also indicated that the impact of exposure to acid on the strength characteristics of concrete becomes more pronounced with prolonged exposure. In addition, the inclusion of NS, SF, and FA in cement concrete results in the development of a unique material that can meet the growing need for construction materials. Furthermore, this technique delivers economic and environmental benefits by minimizing pollution caused by waste products such as FA and SF, which are a residual by-products of thermal power plants and ferrosilicon production respectively.

Preparation and properties of two-dimensional Ti2CT x MXene based on electroetching method

The continuous advancements in wearable electronics have drawn significant attention toward 2D MXenes materials for energy storage owing to their abundant availability, adaptability, and distinctive physicochemical properties. Two unresolved concerns currently revolve around environmental pollution by F-containing etching and finite kinetics caused because of re-stacking of nanosheets. In this study, Al was electrochemically etched from porous Ti2AlC electrodes without the use of fluorine, through a selective electrochemical etching process in dilute hydrochloric acid. Subsequently, Ti2CT x MXene was vertically grown on carbon fiber (CF) substrates. The resulting Ti2CT x @CF electrodes are lightweight, thin, and flexible, exhibiting a surface capacitance of 330 mF cm−2 at a constant current density of 1 mA cm−2 after 2000 cycles. They display a surface capacitance retention of 96.16% and a high energy density of 45.3 μWh cm−2 at a power density of 0.497 mW cm−2. These metrics underscore the Ti2CT x @CF electrode’s commendable multifunctionality, electrochemical performance, ion transport efficiency, and charge storage capacity. Moreover, a flexible energy storage electrode material with a high area capacity was developed by combining Ti2CT x MXene nanosheets, possessing a large specific surface area, with a flexible carbon fabric substrate.

A novel zwitterionic magnetic nanocomposite developed for non-invasive speciation analysis of inorganic chromium

3-(2-Aminoethylamino)propyltriethoxysilane and carboxyethylsilanetriol sodium salt were grafted on silica-coated Fe3O4 nanoparticles via sol-gel process to prepare novel amine- and carboxyl-bifunctionalized magnetic nanocomposites (SMNPs-(NH2 + COOH)). After well characterized, this doubly functionalized material was used as magnetic solid-phase extraction (MSPE) adsorbent to separate and enrich inorganic chromium species followed by inductively coupled plasma-mass spectrometry detection. The optimization of MSPE operation parameters including pH was conducted. It is reasonably elucidated that the adsorption mechanisms of zwitterionic SMNPs-(NH2 + COOH) towards chromium species are electrostatic and/or coordination interactions. Cr(VI) and Cr(III) can be adsorbed around pH 3.0 and around 10.0 respectively with strong anti-interference ability not only from other co-existing ions but also from the two labile species each other, and eluted by dilute nitric acid solution. With a 15-fold enrichment factor, the limits of detection of Cr(VI) and Cr(III) were 0.008 and 0.009 μg L−1, respectively, profiting from the maximum adsorption capacities of 7.52 and 6.11 mg g−1. The just one magnetic extraction matrix based speciation scheme possesses excellent convenience and friendliness to Cr(VI) and Cr(III) without any oxidation or reduction prior to capture of these two species. This protocol has been successfully applied to the speciation analysis of inorganic chromium in real-world environmental water samples.

Investigation and characterization of changes in potato peels by thermochemical acidic pre-treatment for extraction of various compounds

Potato peel waste (PPW) is an underutilized substrate which is produced in huge amounts by food processing industries. Using PPW a feedstock for production of useful compounds can overcome the problem of waste management as well as cost-effective. In present study, potential of PPW was investigated using chemical and thermochemical treatment processes. Three independent variables i.e., PPW concentration, dilute sulphuric acid concentration and liberation time were selected to optimize the production of fermentable sugars (TS and RS) and phenolic compounds (TP). These three process variables were selected in the range of 5–15 g w/v substrate, 0.8–1.2 v/v acid conc. and 4–6 h. Whole treatment process was optimized by using box-behnken design (BBD) of response surface methodology (RSM). Highest yield of total and reducing sugars and total phenolic compounds obtained after chemical treatment was 188.00, 144.42 and 43.68 mg/gds, respectively. The maximum yield of fermentable sugars attained by acid plus steam treatment were 720.00 and 660.62 mg/gds of TS and RS, respectively w.r.t 5% substrate conc. in 0.8% acid with residence time of 6 h. Results recorded that acid assisted autoclaved treatment could be an effective process for PPW deconstruction. Characterization of substrate before and after treatment was checked by SEM and FTIR. Spectras and micrographs confirmed the topographical variations in treated substrate. The present study was aimed to utilize biowaste and to determine cost-effective conditions for degradation of PWW into value added compounds.

Statistical optimization for comparative hydrolysis and fermentation for hemicellulosic ethanolgenesis

The concept of ‘Energy from waste’ is one of the most focused areas of work to find a solution for controlling trash and combat energy crises. In Pakistan and other agricultural countries, because of their substantial use during the summer, watermelon peels as fruit waste are usually thrown out as a trash. This study supported the management of huge quantities of waste to value-added products at a commercial scale. The current study aims to select and subject xylanolytic and ethanologenic Bacillus cereus XG2 for water melon peels valorization appropriately with comparison of three hydrolysis techniques. The study will be helpful for selection of economical and environmentally beneficial valorization strategies. For ethanalogenesis, separate hydrolysis and fermentation (SHF) protocols with Saccharomyces cerevisiae K7 and Metchnikowia cibodasensis Y34 were used. For hydrolysis, three different saccharification approaches, viz. dilute sulfuric acid, enzymatic hydrolysis (using Bacillus cereus XG2 xylanases), and combined acidic and enzymatic hydrolysis, were adopted. Two statistical models, Placket-Burman (hydrolysis) and Central composite design (ethanologenesis) were used. In untreated watermelon waste (WW), reducing sugar, total lipids, total carbohydrates, and protein contents were calculated as 16.70±0.05 g/L, 3.20±0.02 g/L, 28.7±0.04 g/L, and 3.70±0.03 g/L, respectively. Similarly, the lignin (15.51±0.22%), hemicellulose (17.20±2.30%). and cellulose (52.26±0.33%) contents were also analyzed. Based on the significance of the Plackett–Burman model for enzymatic saccharification, the released reducing sugars as well as total sugars were 21.62±0.01 g/L and 43.30±1.55 g/L, respectively, and enzymatic hydrolyzate was adopted for further fermentation experiments. By CCD model, the highest ethanol yield calculated for yeast Metchnikowia cibodasensis Y34 was 0.4±0.04 g/g of fermentable sugars at 32.5oC with 50% enzymatic hydrolysate of WW by incubating for 8 days. It was suggested that SHF could be a beneficial approach to increase the conversion of hemicellulose to fermentable sugars to produce bioethanol on a large scale.

Synthesis Routes of Sulfur-doped Porous Carbon from Mask Wastes for the Application of Supercapacitor Electrodes

Abstract Increasing demand of energy storage devices stimulates growing research in supercapacitors technologies. Waste-based supercapacitor electrodes has become one of areas to be explored as they offer an environmentally friendly approach. Here we synthesis porous carbon from wastes of medical masks which have been generated a lot since the pandemic. Medical masks are composed of polypropylene which have high porosity; hence they have a potential to be used as a porous carbon source for supercapacitor applications. The synthesis routes include a solvothermal process inside a Teflon autoclave in a microwave and a washing process using dilute acid solution and distilled water. The routes successfully transform polypropylene to porous carbon, confirmed by XRD, FTIR, SEM-EDX and Raman spectrum analyses. The present of C-S bond are indicated from FTIR spectrum, implying a successful doping of sulphur into porous carbon. The electrochemical analysis of the prepared electrode using cyclic voltammetry shows an EDLC-like feature with high specific capacitance of ∼375 Fg−1 at the scan rate of 5 mV/s.

Amylase and Cellulase Production from Newly Isolated Bacillus subtilis Using Acid Treated Potato Peel Waste.

Species belonging to the genus Bacillus produce many advantageous extracellular enzymes that have tremendous applications on a commercial scale for the textile, detergent, feed, food, and beverage industries. This study aimed to isolate potent thermo-tolerant amylolytic and cellulolytic bacterium from the local environment. Using the Box-Behnken design of response surface methodology, we further optimized the amylase and cellulase activity. The isolate was identified by 16S rRNA gene sequencing as Bacillus subtilis QY4. This study utilized potato peel waste (PPW) as the biomaterial, which is excessively being dumped in an open environment. Nutritional status of the dried PPW was determined by proximate analysis. All experimental runs were carried out in 250 mL Erlenmeyer flasks containing acid treated PPW as a substrate by the thermos-tolerant Bacillus subtilis QY4 incubated at 37 °C for 72 h of submerged fermentation. Results revealed that the dilute H2SO4 assisted autoclaved treatment favored more amylase production (0.601 IU/mL/min) compared to the acid treatment whereas high cellulase production (1.269 IU/mL/min) was observed in the dilute acid treatment and was found to be very effective compared to the acid assisted autoclaved treatment. The p-value, F-value, and coefficient of determination proved the significance of the model. These results suggest that PPW could be sustainably used to produce enzymes, which offer tremendous applications in various industrial arrays, particularly in biofuel production.

Valorization of Afzelia bella oilseeds cake in bioethanol production using 1-butyl-3-methyl-imidazolium chloride ionic liquid and dilute sulfuric acid pretreatment

The use of renewable feedstocks and the variability of lignocellulosic feedstocks generating fermentable sugars also offer the advantages of the most abundant, sustainable and competitive non-food biomass. The aim of this study is to valorize the oilcake obtained from non-conventional Congolese Afzelia bella oilseeds, after extraction of the oil used in biodiesel production. The conversion of A. bella oilseeds cake into ethanol was carried out using the two methods of pretreatment (with the synthesized ionic liquid 1-butyl-3-methyl imidazolium chloride and dilute sulfuric acid), followed by hydrolysis with dilute sulfuric acid and fermentation by Saccharomyces cerevisiae. The lignocellulosic composition of the sample was 47.98% cellulose, 28.15% hemicellulose and 22.3% lignin. Pretreatment with 1-butyl-3-methyl-imidazolium chloride (ionic liquid) showed an increase in cellulose content of around 4.25% and hemicellulose content of around 7.7%, with simultaneous delignification of 12.25%. In contrast, with dilute sulfuric acid, the lignin and cellulose content of the sample fell to 3.88% and 1.88% respectively. Hemicellulose content, on the other hand, increased by only 3.58%. After dilute acid hydrolysis (5% H2SO4), the values for total reducing sugar, glucose and xylose were 66.06±1.34 mg.g-1; 36.25 ± 1.2 mg.g-1 and 29.71 ± 0.6 mg.g-1 respectively. The percentage conversion of sugars was 55.16 ± 0.5% for cellulose to glucose and 53.76 ± 0.75% for hemicellulose to xylose. The hydrolyzed product of the complex polysaccharide was then converted to ethanol using commercial yeast. Results showed an ethanol yield of around 10.3%, and Fourier Transform Infrared (FTIR) spectroscopy results confirmed bioethanol production. A. bella oilseeds cakes are therefore a potential source for ethanol production.

Mechanistic insights into the plant biostimulant activity of a novel formulation based on rice husk nanobiosilica embedded in a seed coating alginate film.

Seed coating ensures the targeted delivery of various compounds from the early stages of development to increase crop quality and yield. Silicon and alginate are known to have plant biostimulant effects. Rice husk (RH) is a significant source of biosilica. In this study, we coated mung bean seeds with an alginate-glycerol-sorbitol (AGS) film with embedded biogenic nanosilica (SiNPs) from RH, with significant plant biostimulant activity. After dilute acid hydrolysis of ground RH in a temperature-controlled hermetic reactor, the resulting RH substrate was neutralized and calcined at 650°C. The structural and compositional characteristics of the native RH, the intermediate substrate, and SiNPs, as well as the release of soluble Si from SiNPs, were investigated. The film for seed coating was optimized using a mixture design with three factors. The physiological properties were assessed in the absence and the presence of 50 mM salt added from the beginning. The main parameters investigated were the growth, development, metabolic activity, reactive oxygen species (ROS) metabolism, and the Si content of seedlings. The results evidenced a homogeneous AGS film formation embedding 50-nm amorphous SiNPs having Si-O-Si and Si-OH bonds, 0.347 cm3/g CPV (cumulative pore volume), and 240 m2/g SSA (specific surface area). The coating film has remarkable properties of enhancing the metabolic, proton pump activities and ROS scavenging of mung seedlings under salt stress. The study shows that the RH biogenic SiNPs can be efficiently applied, together with the optimized, beneficial alginate-based film, as plant biostimulants that alleviate saline stress from the first stages of plant development.

Chemo-and regioselective aqueous phase, co-acid free nitration of aromatics using traditional and nontraditional activation methods.

Electrophilic aromatic nitrations are used for the preparation of a variety of synthetic products including dyes, agrochemicals, high energy materials, fine chemicals and pharmaceuticals. Traditional nitration methods use highly acidic and corrosive mixed acid systems which present a number of drawbacks. Aside from being hazardous and waste-producing, these methods also often result in poor yields, mostly due to low regioselectivity, and limited functional group tolerance. As a consequence, there is a need for effective and environmentally benign methods for electrophilic aromatic nitrations. In this work, the major aim was to develop reaction protocols that are more environmentally benign while also considering safety issues. The reactions were carried out in dilute aqueous nitric acid, and a broad range of experimental variables, such as acid concentration, temperature, time, and activation method, were investigated. Mesitylene and m-xylene were used as test substrates for the optimization. While the optimized reactions generally occurred at room temperature without any activation under additional solvent-free conditions, slight adjustments in acid concentration, stoichiometric equivalents, and volume were necessary for certain substrates, in addition to the activation. The substrate scope of the process was also investigated using both activated and deactivated aromatics. The concentration of the acid was lowered when possible to improve upon the safety of the process and avoid over-nitration. With some substrates we compared traditional and nontraditional activation methods such as ultrasonic irradiation, microwave and high pressure, respectively, to achieve satisfactory yields and improve upon the greenness of the reaction while maintaining short reaction times.

Enhancing the dilute acid hydrolysis process using a machine learning approach: investigation of different biomass feedstocks influences glucose and ethanol yields

Enhancing the dilute acid hydrolysis process using a machine learning approach: investigation of different biomass feedstocks influences glucose and ethanol yields

Agricultural Waste Management by Production of Second-Generation Bioethanol from Sugarcane Bagasse Using Indigenous Yeast Strain.

In the wake of rapid industrialization and burgeoning transportation networks, the escalating demand for fossil fuels has accelerated the depletion of finite energy reservoirs, necessitating urgent exploration of sustainable alternatives. To address this, current research is focusing on renewable fuels like second-generation bioethanol from agricultural waste such as sugarcane bagasse. This approach not only circumvents the contentious issue of food-fuel conflicts associated with biofuels but also tackles agricultural waste management. In the present study indigenous yeast strain, Clavispora lusitaniae QG1 (MN592676), was isolated from rotten grapes to ferment xylose sugars present in the hemicellulose content of sugarcane bagasse. To liberate the xylose sugars, dilute acid pretreatment was performed. The highest reducing sugars yield was 1.2% obtained at a temperature of 121°C for 15min, a solid-to-liquid ratio of 1:25 (% w/v), and an acid concentration of 1% dilute acid H2SO4 that was significantly higher (P < 0.001) yield obtained under similar conditions at 100°C for 1h. The isolated strain was statistically optimized for fermentation process by Plackett-Burman design to achieve the highest ethanol yield. Liberated xylose sugars were completely utilized by Clavispora lusitaniae QG1 (MN592676) and gave 100% ethanol yield. This study optimizes both fermentation process and pretreatment of sugarcane bagasse to maximize bioethanol yield and demonstrates the ability of isolated strain to effectively utilize xylose as a carbon source. The desirable characteristics depicted by strain Clavispora lusitaniae shows its promising utilization in management of industrial waste like sugarcane bagasse by its conversion into renewable biofuels like bioethanol.

Unlocking the potential of depleted dry batteries: A dual-purpose approach for waste mitigation and sustainable energy production

Electronic-waste (e-waste) poses a serious environmental challenge due to the increasing consumption and disposal of electronic devices. In the present work a novel method is proposed to repurpose e-waste and bio-waste into a single-chamber and mediator-less microbial fuel cells using dead, non-rechargeable D-type dry batteries. The carbonaceous material inside the dry batteries was replaced with kitchen waste sludge, which served as the substrate. The outer zinc casing was also reused as the anode and the carbon rod as the cathode. Treating the kitchen waste sludge with dilute nitric acid improved the performance of the microbial fuel cells by enhancing the biodegradability and conductivity of the substrate. The untreated microbial fuel cells produced a maximum power density of 15.0 mW/kg at a maximum current density of 50.0 mA/kg, while the treated microbial fuel cells achieved 67.0 mW/kg at 178.0 mA/kg. The main mechanism behind the working of the device is the combined action of galvanic and microbial processes, which synergistically generate electricity from e-waste and bio-waste. Moreover, when four treated microbial fuel cells were connected in series, a high open circuit voltage of 3.3 V was achieved. These microbial fuel cells stand out as eco-conscious and lightweight alternatives to conventional dry batteries, presenting an environmentally sustainable solution for waste management and clean energy production.

Scaling high-speed counter-current chromatography for preparative neodymium purification: Insights and challenges

Efficient rare earth element (REE) separations are becoming increasingly important to technologies ranging from renewable energy and high-performance magnets to applied radioisotope separations. These separations are made challenging by the extremely similar chemical and physical characteristics of the individual elements, which almost always occupy the 3+ oxidation state under ambient conditions. Herein, we discuss the development of a novel REE separation aimed at obtaining purified samples of neodymium (Nd) on a multi-milligram scale using high-speed counter-current chromatography (HSCCC). The method takes advantage of the subtle differences in ionic radii between neighboring REEs to tune elution rates in dilute acid through implementation of the di-(2-ethylhexyl)phosphoric acid (HDEHP)-infused stationary phase (SP) of the column. A La/Ce/Nd/Sm separation was demonstrated at a significantly higher metal loading than previously accomplished by HSCCC (15 mg, RNd/REE > 0.85), while the Pr/Nd separation was achieved at lower metal loadings (0.3 mg, RNd/Pr = 0.75 – 0.83). The challenges associated with scaling REE separations via HSCCC are presented and discussed within.

Effect of glass frit composition on reliability of silver paste metallization in crystalline silicon solar cells

Glass frit used in conductive silver (Ag) pastes has a significant impact not only on the electrical performance but also on the long-term reliability of metallized electrodes in crystalline silicon (c-Si) solar cells. Here, we investigated the role of compositional changes on the metallization process of silver pastes by adjusting the SiO2, ZnO, Li2O, or Bi2O3 in lead borate glass melts, and performed damp heat (DH) tests in an acidic damp heat environment. It was found that the addition of Bi2O3 resulted in a decrease in conversion efficiency (Eta) of only 6.44% after the cell was treated with dilute acetic acid. Under scanning electron microscopy (SEM), it was observed that the cell with this glass frit had minimal changes in the microstructure of its silver-silicon contacts and silver electrodes. This finding helps to improve the performance and stability of solar cells in harsh environments.

De-risking Pretreatment of Microalgae To Produce Fuels and Chemical Co-products.

Conversion of microalgae to renewable fuels and chemical co-products by pretreating and fractionation holds promise as an algal biorefinery concept, but a better understanding of the pretreatment performance as a function of algae strain and composition is necessary to de-risk algae conversion operations. Similarly, there are few examples of algae pretreatment at scales larger than the bench scale. This work aims to de-risk algal biorefinery operations by evaluating the pretreatment performance across nine different microalgae samples and five different pretreatment methods at small (5 mL) scale and further de-risk the operation by scaling pretreatment for one species to the 80 L scale. The pretreatment performance was evaluated by solubilization of feedstock carbon and nitrogen [as total organic carbon (TOC) and total nitrogen (TN)] into the aqueous hydrolysate and extractability of lipids [as fatty acid methyl esters (FAMEs)] from the pretreated solids. A range of responses was noted among the algae samples across pretreatments, with the current dilute Brønsted acid pretreatment using H2SO4 being the most consistent and robust. This pretreatment produced TOC yields to the hydrolysate ranging from 27.7 to 51.1%, TN yields ranging from 12.3 to 76.2%, and FAME yields ranging from 57.9 to 89.9%. In contrast, the other explored pretreatments (other dilute acid pretreatments, dilute alkali pretreatment with NaOH, enzymatic pretreatment, and flash hydrolysis) produced lower or more variable yields across the three metrics. In light of the greater consistency across samples for dilute acid pretreatment, this method was scaled to 80 L to demonstrate scalability with microalgae feedstocks.

Selective Removal of Hemicellulose by Diluted Sulfuric Acid Assisted by Aluminum Sulfate.

Hemicellulose can be selectively removed by acid pretreatment. In this study, selective removal of hemicellulose was achieved using dilute sulfuric acid assisted by aluminum sulfate pretreatment. The optimal pretreatment conditions were 160 °C, 1.5 wt% aluminum sulfate, 0.7 wt% dilute sulfuric acid, and 40 min. A component analysis showed that the removal rate of hemicellulose and lignin reached 98.05% and 9.01%, respectively, which indicated that hemicellulose was removed with high selectivity by dilute sulfuric acid assisted by aluminum sulfate pretreatment. Structural characterizations (SEM, FTIR, BET, TGA, and XRD) showed that pretreatment changed the roughness, crystallinity, pore size, and functional groups of corn straw, which was beneficial to improve the efficiency of enzymatic hydrolysis. This study provides a new approach for the high-selectivity separation of hemicellulose, thereby offering novel insights for its subsequent high-value utilization.

Valorisation of bread wastes via the bacterial cellulose production

AbstractThe short shelf life of bread can be attributed to changes in its textural and sensory properties, a process termed staling, and large amounts of bread residue and waste are generated daily. Because the main component of bread is starch, the use of bread wastes as a substrate for bacterial cellulose (BC) production can significantly contribute to valorisation and reuse of wastes. This study aimed to investigate the BC production potential of various stale breads, convert these wastes into usable forms for food and other industries, and increase their economic value. Stale breads were hydrolyzed with dilute acid, and BC-producing bacteria from Kombucha tea were isolated and identified as Gluconobacter oxydans MG2021 (GO). BCs were produced from bread hydrolysates with GO and Komagataeibacter hansenii GA2016 (KH), and their properties were examined. The results indicated that stale breads represented a good source for BC production, as high BC yields were obtained using GO (8.81%–25.02%) and all BCs had superior properties such as high crystallinity (75.96%–91.39%), thermal stability, liquid holding capacity, and fine fibers (40.16–85.39 nm). This study demonstrated that bread wastes could be used as a low-cost substrate for large-scale BC production, and the abundance of bread wastes demonstrated their potential as a resource for commercial BC producers.

Integration of lactic acid biorefinery with treatment of red mud from alumina refinery: win–win paradigm for waste valorization

The cost of detoxification and neutralization poses certain challenges to the development of an economically viable lactic acid biorefinery with lignocellulosic biomass as feedstock. Herein, red mud, an alkaline waste, was explored as both a detoxifying agent and a neutralizer. Red mud treatment of lignocellulosic hydrolysate effectively removed the inhibitors generated in dilute acid pretreatment, improving the lactic acid productivity from 1.0 g/L·h−1 to 1.9 g/L·h−1 in later fermentation. In addition, red mud could replace CaCO3 as a neutralizer in lactic acid fermentation, which in turn enabled simultaneous bioleaching of valuable metals (Sc, Y, Nd, and Al) from red mud. The neutralization of alkali in red mud by acids retained in lignocellulosic hydrolysate and lactic acid produced from fermentation led to effective dealkalization, rendering a maximum alkali removal efficiency of 92.2 %. Overall, this study offered a win–win strategy for the valorization of both lignocellulosic biomass and red mud.