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Alya Limayem

Bio: Alya Limayem is an academic researcher from University of Arkansas. The author has contributed to research in topics: HYDROSOL & Bioenergy. The author has an hindex of 2, co-authored 2 publications receiving 1039 citations.

Papers
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Journal ArticleDOI
TL;DR: A review of the major steps involved in cellulosic-based bioethanol processes and potential issues challenging these operations is provided in this paper, where possible solutions and recoveries that could improve bioprocessing are also addressed.

1,172 citations

Journal ArticleDOI
TL;DR: Alternative antimicrobials proved to be a potential candidate for controlling bacterial contamination in the fermentation process as synergy effect of nisin with EDTA successfully inhibited the nisin-resistant contaminant, L. casei.
Abstract: Antibiotics are commonly used to control microbial contaminants in yeast-based bioethanol fermentation. Given the increase in antibiotic-resistant bacteria, alternative natural antimicrobials were evaluated against the potential contaminant, Lactobacillus. The effects of nisin, ϵ-polylysine, chitosan (CS) and lysozyme were screened against 5 Lactobacillus strains. A standard broth- microdilution method was used in 96-well plates to assess the minimal inhibitory concentration (MIC). L. delbrueckii subsp lactis ATCC479 exhibited maximal MICs with CS, ϵ-polylysine and nisin (1.87, 0.3125 and 0.05 mg/mL, respectively). Nisin reduced most Lactobacillus strains by 6 log CFU/mL after 48 hours with the exception of L. casei. Synergism occurred when ethylenediaminetetraacetic acid (EDTA) was added with nisin. An MIC of 0.4 mg/mL of nisin combined with the EDTA at an MIC of 1 mg/ml markedly suppressed L .casei by 6 log CFU/mL. In conclusion, alternative antimicrobials proved to be a potential candidate for controlling bacterial contamination in the fermentation process. Synergistic effect of nisin with EDTA successfully inhibited the nisin-resistant contaminant, L. casei.

20 citations

Journal ArticleDOI
TL;DR: In this article , the effect of bioactive Ag-hydrosol nanoparticles (NPs) on drug-resistant E. faecium 1449 strain and explore the use of artificial intelligence (AI) for automated detection of the bacteria.
Abstract: Introduction Silver (Ag) nanoparticles (NPs) are well documented for their broad-spectrum bactericidal effects. This study aimed to test the effect of bioactive Ag-hydrosol NPs on drug-resistant E. faecium 1449 strain and explore the use of artificial intelligence (AI) for automated detection of the bacteria. Methods The formation of E. faecium 1449 biofilms in the absence and presence of Ag-hydrosol NPs at different concentrations ranging from 12.4 mg/L to 123 mg/L was evaluated using a 3-dimentional culture system. The biofilm reduction was evaluated using the confocal microscopy in addition to the Transmission Electronic Microscopy (TEM) visualization and spectrofluorimetric quantification using a Biotek Synergy Neo2 microplate reader. The cytotoxicity of the NPs was evaluated in human nasal epithelial cells using the MTT assay. The AI technique based on Fast Regional Convolutional Neural Network architecture was used for the automated detection of the bacteria. Results Treatment with Ag-hydrosol NPs at concentrations ranging from 12.4 mg/L to 123 mg/L resulted in 78.09% to 95.20% of biofilm reduction. No statistically significant difference in biofilm reduction was found among different batches of Ag-hydrosol NPs. Quantitative concentration-response relationship analysis indicated that Ag-hydrosol NPs exhibited a relative high anti-biofilm activity and low cytotoxicity with an average EC50 and TC50 values of 0.0333 and 6.55 mg/L, respectively, yielding an average therapeutic index value of 197. The AI-assisted TEM image analysis allowed automated detection of E. faecium 1449 with 97% ~ 99% accuracy. Discussion Conclusively, the bioactive Ag-hydrosol NP is a promising nanotherapeutic agent against drug-resistant pathogens. The AI-assisted TEM image analysis was developed with the potential to assess its treatment effect.

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Journal ArticleDOI
TL;DR: A broad review of the state-of-the-art biomass pyrolysis research can be found in this article, where three major components (cellulose, hemicellulose and lignin) are discussed in detail.

1,613 citations

Journal ArticleDOI
TL;DR: This review provides a summary and perspective of the extensive research that has been devoted to each of these three interconnected biorefinery aspects, ranging from industrially well-established techniques to the latest cutting edge innovations.
Abstract: In pursuit of more sustainable and competitive biorefineries, the effective valorisation of lignin is key. An alluring opportunity is the exploitation of lignin as a resource for chemicals. Three technological biorefinery aspects will determine the realisation of a successful lignin-to-chemicals valorisation chain, namely (i) lignocellulose fractionation, (ii) lignin depolymerisation, and (iii) upgrading towards targeted chemicals. This review provides a summary and perspective of the extensive research that has been devoted to each of these three interconnected biorefinery aspects, ranging from industrially well-established techniques to the latest cutting edge innovations. To navigate the reader through the overwhelming collection of literature on each topic, distinct strategies/topics were delineated and summarised in comprehensive overview figures. Upon closer inspection, conceptual principles arise that rationalise the success of certain methodologies, and more importantly, can guide future research to further expand the portfolio of promising technologies. When targeting chemicals, a key objective during the fractionation and depolymerisation stage is to minimise lignin condensation (i.e. formation of resistive carbon–carbon linkages). During fractionation, this can be achieved by either (i) preserving the (native) lignin structure or (ii) by tolerating depolymerisation of the lignin polymer but preventing condensation through chemical quenching or physical removal of reactive intermediates. The latter strategy is also commonly applied in the lignin depolymerisation stage, while an alternative approach is to augment the relative rate of depolymerisation vs. condensation by enhancing the reactivity of the lignin structure towards depolymerisation. Finally, because depolymerised lignins often consist of a complex mixture of various compounds, upgrading of the raw product mixture through convergent transformations embodies a promising approach to decrease the complexity. This particular upgrading approach is termed funneling, and includes both chemocatalytic and biological strategies.

1,466 citations

Journal ArticleDOI
TL;DR: Nanocellulose has excellent strength, high Young's modulus, biocompatibility, and tunable self-assembly, thixotropic, and photonic properties, which are essential for the applications of this material.
Abstract: With increasing environmental and ecological concerns due to the use of petroleum-based chemicals and products, the synthesis of fine chemicals and functional materials from natural resources is of great public value. Nanocellulose may prove to be one of the most promising green materials of modern times due to its intrinsic properties, renewability, and abundance. In this review, we present nanocellulose-based materials from sourcing, synthesis, and surface modification of nanocellulose, to materials formation and applications. Nanocellulose can be sourced from biomass, plants, or bacteria, relying on fairly simple, scalable, and efficient isolation techniques. Mechanical, chemical, and enzymatic treatments, or a combination of these, can be used to extract nanocellulose from natural sources. The properties of nanocellulose are dependent on the source, the isolation technique, and potential subsequent surface transformations. Nanocellulose surface modification techniques are typically used to introduce e...

864 citations

Journal ArticleDOI
01 Aug 2015
TL;DR: Mechanisms and recent advances in pretreatment, cellulases production and second-generation ethanol production processes are described here.
Abstract: Production of liquid biofuels, such as bioethanol, has been advocated as a sustainable option to tackle the problems associated with rising crude oil prices, global warming and diminishing petroleum reserves. Second-generation bioethanol is produced from lignocellulosic feedstock by its saccharification, followed by microbial fermentation and product recovery. Agricultural residues generated as wastes during or after processing of agricultural crops are one of such renewable and lignocellulose-rich biomass resources available in huge amounts for bioethanol production. These agricultural residues are converted to bioethanol in several steps which are described here. This review enlightens various steps involved in production of the second-generation bioethanol. Mechanisms and recent advances in pretreatment, cellulases production and second-generation ethanol production processes are described here.

813 citations

Journal ArticleDOI
TL;DR: An overview on the diversity of biomass, technological approaches and microbial contribution to the conversion of lignocellulosic biomass (LCB) into ethanol can be found in this paper.
Abstract: Bioethanol is one of the most promising and eco-friendly alternatives to fossil fuels, which is produced from renewable sources. Although almost all the current fuel ethanol is generated from edible sources (sugars and starch), lignocellulosic biomass (LCB) has drawn much attention in recent times. However, the conversion efficiency as well as ethanol yield of the biomass differs greatly with respect to the source and nature of LCB, primarily due to the variation in lignocellulosic content. Two major polysaccharides in LCB, namely, cellulose and hemicellulose firmly link to lignin and form a complex lignocellulosic network, which is highly robust and recalcitrant to depolymerization. For this reason, generation of ethanol from LCB requires a complicated conversion process that has made it commercially non-competitive. As attempts to exploit LCBs into commercial ethanol production, recent research efforts have been devoted to the techno-economic improvements of the overall conversion process, in addition to screen out promising feedstocks. This review paper presents an overview on the diversity of biomass, technological approaches and microbial contribution to the conversion of LCB into ethanol.

536 citations