Mechanistic investigation in ultrasound induced enhancement of enzymatic hydrolysis of invasive biomass species

Review of fish protein hydrolysates: production methods, antioxidant and antimicrobial activity and nanoencapsulation

Marine products have gained popularity due to their valuable components, especially protein, despite generating significant waste. Protein hydrolysates are widely recognized as the most effective method for transforming these low-value raw materials into high-value products. Fish protein hydrolysate (FPH), sourced from various aquatic wastes such as bones, scales, skin, and others, is rich in protein for value-added products. However, the hydrophobic peptides have limitations like an unpleasant taste and high solubility. Microencapsulation techniques provide a scientific approach to address these limitations and safeguard bioactive peptides. This review examines current research on FPH production methods and their antioxidant and antibacterial activities. Enzymatic hydrolysis using commercial enzymes is identified as the optimal method, and the antioxidant and antibacterial properties of FPH are substantiated. Microencapsulation using nanoliposomes effectively extends the inhibitory activity and enhances antioxidant and antibacterial capacities. Nevertheless, more research is needed to mitigate the bitter taste associated with FPH and enhance sensory attributes.

Environment friendly emerging techniques for the treatment of waste biomass: a focus on microwave and ultrasonication processes

In the recent past, an increasing interest is mostly observed in using microwave and ultrasonic irradiation to aid the biological conversion of waste materials into value-added products. This study is focused on various individual impacts of microwaves and ultrasonic waves for the treatment of biomass before the synthesis of value-added products. Following, a comprehensive review of the mechanisms governing microwaves and ultrasonication as the treatment methods, their effects on biomass disruption, solubilization of organic matter, modification of the crystalline structure, enzymatic hydrolysis and production of reducing sugars was performed. However, based on the lab-scale experiments evaluated, microwaves and ultrasonication were studied to be economically and energetically ineffective despite their beneficial effects on the waste biomass. This article reviews some of the difficulties associated with using microwaves and ultrasonic irradiation for the efficient processing of waste biomasses and identified some potential directions for future study.

Influence of Low-Intensity Ultrasound on ε-Polylysine Production: Intracellular ATP and Key Biosynthesis Enzymes during Streptomyces albulus Fermentation

The effect of low-intensity sonication treatment on cell growth, ε-polylysine (ε-PL) yield and its biological mechanism were investigated, using a 3-L-jar fermenter coupled with an in situ ultrasonic slot with a Streptomyces albulus strain SAR 14-116. Under ultrasonic conditions (28 kHz, 0.37 W cm−2, 60 min), a high biomass of SAR 14-116 and concentration of ε-PL were realized (i.e., they increased by 14.92% and 28.45%, respectively) when compared with a control. Besides this, ultrasonication increased the mycelia viability and intracellular ATP as well as activities of key enzymes involved in the ε-PL biosynthesis pathway, resulting in an improvement in the production of ε-PL. Data on qRT-PCR revealed that ultrasonication also affected the gene expression of key enzymes in the ε-PL biosynthesis pathway, including ε-PL synthetase (PLS). These outcomes provided the basis for understanding the effects of ultrasound-assisted fermentation on the stimulation of metabolite production and fermentation procedure in a fermenter.

Ultrasonic cavitation: An effective cleaner and greener intensification technology in the extraction and surface modification of nanocellulose

With rising consumer demand for natural products, a greener and cleaner technology, i.e., ultrasound-assisted extraction, has received immense attention given its effective and rapid isolation for nanocellulose compared to conventional methods. Nevertheless, the application of ultrasound on a commercial scale is limited due to the challenges associated with process optimization, high energy requirement, difficulty in equipment design and process scale-up, safety and regulatory issues. This review aims to narrow the research gap by placing the current research activities into perspectives and highlighting the diversified applications, significant roles, and potentials of ultrasound to ease future developments. In recent years, enhancements have been reported with ultrasound assistance, including a reduction in extraction duration, minimization of the reliance on harmful chemicals, and, most importantly, improved yield and properties of nanocellulose. An extensive review of the strengths and weaknesses of ultrasound-assisted treatments has also been considered. Essentially, the cavitation phenomena enhance the extraction efficiency through an increased mass transfer rate between the substrate and solvent due to the implosion of microbubbles. Optimization of process parameters such as ultrasonic intensity, duration, and frequency have indicated their significance for improved efficiency.

Process optimization and characterization of arachidonic acid oil degumming using ultrasound-assisted enzymatic method

Ultrasound assisted enzymatic method was applied to the degumming of arachidonic acid (ARA) oil produced by Mortierella alpina. The conditions of degumming process were optimized by response surface methodology with Box- Behnken design. A dephosphorization rate of 98.82% was achieved under optimum conditions of a 500 U/kg of Phospholipase A₁ (PLA₁) dosage, 2.8 mL/100 g of water volume, 120 min of ultrasonic time, and 135 W of ultrasonic power. The phosphorus content of ultrasonic assisted enzymatic degumming oil (UAEDO) was 4.79 mg/kg, which was significantly lower than that of enzymatic degumming oil (EDO, 17.98 mg/kg). Crude Oil (CO), EDO and UAEDO revealed the similar fatty acid compositions, and ARA was dominated (50.97 ~ 52.40%). The oxidation stability of UAEDO was equivalent to EDO and weaker than CO, while UAEDO presented the strongest thermal stability, followed by EDO and CO. Furthermore, aldehydes, acids and alcohols were identified the main volatile flavor components for the three oils. The proportions of major contributing components such as hexanal, nonanal, (E)-2-nonanal, (E, E)-2,4-decadienal, (E)-2-nonenal and aldehydes in UAEDO and EDO were all lower than CO. Overall, Ultrasound assisted enzymatic degumming proved to be an efficient and superior method for degumming of ARA oil.

Rhododendron and Japanese Knotweed: invasive species as innovative crops for second generation biofuels for the ionoSolv process

We investigated the potential of two terrestrial biomass invasive species in the United-Kingdom as lignocellulosic biofuel feedstocks: Japanese Knotweed (Fallopia japonica) and Rhododendron (Rhododendron ponticum). We demonstrate that a pretreatment technique using a low-cost protic ionic liquid, the ionoSolv process, can be used for such types of plant species considered as waste, to allow their integration into a biorefinery. N,N,N-Dimethylbutylammonium hydrogen sulfate ([DMBA][HSO₄]) was able to fractionate the biomass into a cellulose-rich pulp and a lignin stream at high temperatures (150–170 °C) and short reaction times (15–60 minutes). More than 70–80% of the subsequent cellulose was hydrolysed into fermentable sugars, which were fermented into the renewable energy vector bioethanol.

Japanese Knotweed (Fallopia japonica) and Rhododendron (Rhododendron ponticum), two invasive species in the UK that are an environmental threat and economic burden, can be integrated into a flexible ionic liquid based biorefinery process to produce bioenergy and chemicals.

Sono- and mechanochemical technologies in the catalytic conversion of biomass

This tutorial review focuses on the valorisation of biomass by sonochemical and mechanochemical activation.

Ultrasound-assisted production of biodiesel using engineered methanol tolerant Proteus vulgaris lipase immobilized on functionalized polysulfone beads

In the present study, Proteus vulgaris lipase (PVL) was engineered using directed evolution to increase methanol tolerance so that it would be more tolerant and efficient for harsh conditions employed in biodiesel synthesis, which is limiting their industrial use. The influence of ultrasound under different experimental conditions on the biodiesel conversion yield using methanolysis of non-edible neem oil was also emphasized. A special attention was also paid to the immobilization of lipase on Polysulfone (PS) beads and comparative studies with industrially used Burkholderia cepacia lipase. The Engineered Proteus vulgaris lipase showed >80% activity after 3 h when incubated in 50% methanol with simultaneous sonication. The lipase retained improved longevity (~70% residual activity) over wild-type PVL over repeated use.

Combining Autoclaving with Mild Alkaline Solution as a Pretreatment Technique to Enhance Glucose Recovery from the Invasive Weed Chloris barbata

Developing an optimum pretreatment condition to enhance glucose recovery assessed the potential of Chloris barbata, which is a common invasive weed in Thailand, as a feedstock for bioethanol production. Chloris barbata was exposed to autoclave-assisted alkaline pretreatment by using different sodium hydroxide (NaOH) concentrations (1% to 4%) and heat intensities (110 °C to 130 °C) that were dissipated from autoclaving. The optimum condition for pretreatment was determined to be 2% NaOH at 110 °C for 60 min. At this condition, maximum hydrolysis efficiency (90.0%) and glucose recovery (30.7%), as compared to those of raw C. barbata (15.15% and 6.20%, respectively), were observed. Evaluation of glucose production from 1000 g of C. barbata based on material balance analysis revealed an estimated yield of 304 g after pretreatment at the optimum condition when compared to that of raw C. barbata (61 g), an increase of five-fold. Structural analysis by the scanning electron microscopy (SEM) and X-ray diffraction (XRD) revealed the disruption of the intact structure of C. barbata and an increase in the cellulose crystallinity index (CrI), respectively. The results from this study demonstrate the efficiency of using C. barbata as a potential feedstock for bioethanol production.

Physical insights of ultrasound-assisted ethanol production from composite feedstock of invasive weeds

Invasive weeds ubiquitously found in terrestrial and aquatic ecosystems form potential feedstock for lignocellulosic ethanol production. The present study has reported a bioprocess for production of ethanol using mixed feedstock of 8 invasive weeds found in India. The feedstock was subjected to pretreatment comprising dilute acid hydrolysis (for hydrolysis of hemicellulosic fraction), alkaline delignification and enzymatic hydrolysis of cellulosic fraction. Pentose-rich and hexose-rich hydrolyzates obtained from pretreatment were fermented separately using microbial cultures of S. cerevisiae and C. shehatae. Fermentation mixture was sonicated at 35 kHz at 10% duty cycle. The time profiles of total reducing sugars, ethanol and biomass was fitted to a kinetic model using Genetic Algorithm. Sonication boosted the kinetics of fermentation 2-fold. The net bioethanol yield of the process was ∼220 g/kg raw biomass (with contributions of 86.8 and 133 g/kg raw biomass from pentose and hexose fermentations, respectively). Comparative evaluation of parameters of kinetic model under control and test conditions revealed several beneficial influences of sonication on both pentose and hexose fermentation systems such as faster transport of nutrients, substrate and products across cell membrane, rise in Monod saturation constant for substrate with concurrent reduction in substrate inhibition, and reduction of energy requirements for cell maintenance. Flow cytometry analysis of native and ultrasound-treated cells revealed no adverse influence of sonication on cell viability.

Mechanistic investigations in biobutanol synthesis via ultrasound-assisted ABE fermentation using mixed feedstock of invasive weeds

This study reports an ultrasound-assisted Acetone-Butanol-Ethanol (ABE) fermentation process using Clostridium acetobutylicum MTCC 11,274 and mixed feedstock consisting of eight highly invasive weeds. Composite (pentose + hexose) hydrolyzate was fermented with sonication at 35 kHz and 10% duty cycle (test) and mechanical agitation at 150 rpm (control). Net solvent yield with sonication was 0.288 g/g raw biomass in 92 h against yield of 0.168 g/g raw biomass in 120 h with mechanical agitation. Butanol yield in test and control fermentation was 0.233 and 0.149 g/g total fermentable sugar, respectively. Substrate and metabolites profiles in test and control fermentation were analyzed using biokinetic model. Sonication enhanced kinetics of metabolic reactions with rise in substrate affinity of enzymes (reduced saturation constants) and greater resistance to substrate inhibition. Flow cytometry analysis of cells exposed to sonication revealed high cell viability with no adverse effect on physiology.

Chemical and structural changes of pretreated empty fruit bunch (EFB) in ionic liquid-cellulase compatible system for fermentability to bioethanol

The pretreatment of empty fruit bunch (EFB) was conducted using an integrated system of IL and cellulases (IL-E), with simultaneous fermentation in one vessel. The cellulase mixture (PKC-Cel) was derived from Trichoderma reesei by solid-state fermentation. Choline acetate [Cho]OAc was utilized for the pretreatment due to its biocompatibility and biodegradability. The treated EFB and its hydrolysate were characterized by the Fourier transform infrared spectroscopy, scanning electron microscopy, and chemical analysis. The results showed that there were significant structural changes in EFB after the treatment in IL-E system. The sugar yield after enzymatic hydrolysis by the PKC-Cel was increased from 0.058 g/g of EFB in the crude sample (untreated) to 0.283 and 0.62 ± 06 g/g in IL-E system after 24 and 48 h of treatment, respectively. The EFB hydrolysate showed the eligibility for ethanol production without any supplements where ethanol yield was 0.275 g ethanol/g EFB in the presence of the IL, while lower yield obtained without IL-pretreatment. Moreover, it was demonstrated that furfural and phenolic compounds were not at the level of suppressing the fermentation process.

Investigations in ultrasound-induced enhancement of astaxanthin production by wild strain Phaffia rhodozyma MTCC 7536

This work reports ultrasound-induced enhancement of astaxanthin production in batch fermentation using wild strain of P. rhodozyma MTCC 7536. The methodology adopted in this study comprises of statistical optimization of the medium and fermentation parameters, followed by application of sonication at optimized conditions. P. rhodozyma fermentation at conditions of 20 g/L glucose, pH 4.4, temperature 21 °C, 4% v/v inoculum, shaking at 205 rpm with nitrogen sources of (NH₄)₂SO₄ and yeast extract yielded 6.8 mg/L or 1360 μg/g DCW astaxanthin in 84 h. Application of 33 kHz and 140 kPa sonication at 10% duty cycle in final 12 h of fermentation enhanced the astaxanthin yield to 8.6 mg/L or 1728 μg/g DCW, which is higher than several mutant strains reported in literature. These results are essentially manifestations of intense microturbulence generated by sonication in fermentation mixture.

Ultrasound-assisted biological conversion of biomass and waste materials to biofuels: A review

Ultrasound irradiation has been gaining increasing interests over the years to assist biological conversion of lignocellulosic biomass and waste materials to biofuels. As such, this study reviewed the different effects of sonication on pre-treatment of lignocellulosic biomass and waste materials prior to biofuel production. The mechanisms of ultrasound irradiation as a pre-treatment technique were initially described and the impacts of sonication on disruption of lignocellulosic materials, alteration of the crystalline lattice structure of cellulose molecules, solubilisation of organic matter, reducing sugar production and enzymatic hydrolysis were then reviewed. Subsequently, the influences of ultrasound irradiation on bio-methane, bio-hydrogen and bio-ethanol production were re-evaluated, with most studies reporting enhanced biofuel production from anaerobic digestion or fermentation processes. Nonetheless, despite its positive impacts on biofuel production, sonication was found to be energetically inefficient based on the lab-scale studies reviewed. To conclude, this study reviewed some of the challenges of ultrasound irradiation for enhanced biofuel production while outlining some areas for further research.

Metabolic flux network analysis of hydrogen production from crude glycerol by Clostridium pasteurianum

The present study has attempted to get insight into ultrasound induced enhancement in biohydrogen production from glycerol fermentation using metabolic flux analysis (MFA). A pseudo steady state metabolic flux network model was constructed and analyzed using experimentally measured glycerol uptake rate and fluxes of four metabolites, viz. acetate, butyrate, succinate and 1,3-PDO. Glycerol consumption increased by ∼50% under sonication. Biohydrogen yield showed marked rise of ∼40% with application of ultrasound. Butyrate and 1,3-PDO were the major products of glycerol metabolism. Sonication had major influence on carbon fluxes at the acetyl-CoA node. MFA results revealed enhanced flux towards butyrate under sonication, which was manifested in higher butyrate to acetate (B/A) ratio in products and greater H₂ generation. Biohydrogen production was also a microbial growth associated process. Finally, two theoretical alternatives for further enhancement of biohydrogen production were assessed with MFA, viz. enhancement of glycerol uptake and blocking of butyrate pathway.

Microbial production, ultrasound-assisted extraction and characterization of biopolymer polyhydroxybutyrate (PHB) from terrestrial (P. hysterophorus) and aquatic (E. crassipes) invasive weeds

This study reports synthesis of biodegradable poly(3-hydroxybutyrate) (PHB) polymer from two invasive weeds, viz. P. hysterophorus and E. crassipes. The pentose and hexose-rich hydrolyzates obtained from acid pretreatment and enzymatic hydrolysis of two biomasses were separately fermented using Ralstonia eutropha MTCC 8320 sp. PHB was extracted using sonication and was characterized using FTIR, ¹H and ¹³C NMR and XRD. PHB content of dry cell mass was 8.1-21.6% w/w, and the PHB yield was 6.85×10^-3-36.41×10^-3% w/w raw biomass. Thermal properties of PHB were determined by TGA, DTG and DSC analysis. PHB obtained from pentose-hydrolyzate had glass transition temperatures of 6°-9°C, while PHB from hexose-rich hydrolyzate had maximum thermal degradation temperatures of 370°-389°C. These thermal properties were comparable to the properties of commercial PHB. Probable causes leading to differences in thermal properties of pentose and hexose-derived PHB are: extent of crystallinity and presence of impurity in the polymer matrix.

An investigation of lipase catalysed sonochemical synthesis: A review

Ultrasonic irradiation has recently gained attention of researchers for its process intensification in numerous reactions. Earlier ultrasound was known for its application either to deactivate enzyme activity or to disrupt the cell. However, in recent years, practice of ultrasonic irradiation began to emerge as a tool for the activation of the enzymes under mild frequency conditions. The incorporation of ultrasound in any of enzymatic reactions not only increases yield but also accelerates the rate of reaction in the presence of mild conditions with better yield and less side-products. To attain maximum yield, it is crucial to understand the mechanism and effect of sonication on reaction especially for the lipase enzyme. Thus, the influence of ultrasound irradiation on reaction yield for different parameters including temperature, enzyme concentration, mole ratio of substrates, solvents ultrasonic frequency and power was reviewed and discussed. The physical effect of cavitation determined by bubble dynamics and rate of reaction through kinetic modelling also needs to be assessed for complete investigation and scale up of synthesis. Thus, prudish utilisation of ultrasound for enzymatic synthesis can serve better future for sustainable and green chemistry.

Ultrasonic accelerates asparagine-glucose non-enzymatic browning reaction without acrylamide formation

Ultrasonic accelerated the asparagine-glucose non-enzymatic browning reaction with significant decrease of glucose and asparagine concentrations, and marked increase of intermediate products (UV-absorbance value at 294nm, Abs₂₉₄), melanoidins (UV-absorbance value at 420nm, Abs₄₂₀) and in vitro antioxidant activity (DPPH free radical scavenging activity). As the ultrasonic intensity was 17.83W/cm², the asparagine-glucose solution's Abs₂₉₄, Abs₄₂₀ and antioxidant activity increased from 0 to 1.26, 0.88 and 21.56%, respectively, and the glucose and asparagine concentrations of the asparagine-glucose solution reduced 58.97 and 12.57%, respectively. The high performance liquid chromatography (HPLC)-Diode Array Detector (DAD) analyses showed that no acrylamide was detected after 50-min ultrasonic reaction. This study suggested that ultrasonic at higher intensity was a potential method to accelerate the non-enzymatic browning reaction in the asparagine-glucose solution without acrylamide production.

Ultrasound-enhanced enzymatic hydrolysis of poly(ethylene terephthalate)

The application of ultrasound was found to enhance enzymatic hydrolysis of poly(ethylene terephthalate) (PET). After a short activation phase up to 6.6times increase in the amount of released products was found. PET powder with lower crystallinity of 8% was hydrolyzed faster when compared to PET with 28% crystallinity. Ultrasound activation was found to be around three times more effective on powders vs. films most likely due to a larger surface area accessible to the enzyme.

Proper ultrasound treatment increases ethanol production from simultaneous saccharification and fermentation of sugarcane bagasse

To improve the saccharification and fermentation processes, proper ultrasound was applied which resulted in the presence of cellulase complex with improved β-glucosidase ratio leading to enhanced overall ethanol yield.

An assessment of the potential of invasive weeds as multiple feedstocks for biofuel production

The present study assessed the feasibility of five invasive weeds, namely, Arundo donax, Saccharum spontaneum, Mikania mikrantha, Lantana camara and Eichhornia crasspies, as a feedstock for biofuels production.

Ultrasound-assisted bioalcohol synthesis: review and analysis

The present article highlights the efficacy of ultrasound in the intensification of all the steps of bioalcohol synthesis with a critical analysis of the literature.