Electrochemical nano-biosensor systems are popular in the industrial field, along with evaluations of medical, agricultural, environmental and sports analysis, because they can simultaneously perform qualitative and quantitative analyses with high sensitivity. However, real-time detection using an electrochemical nano-biosensor is greatly affected by the surrounding environment with the performance of the electron transport materials. Therefore, many researchers are trying to find good factors for real-time detection. In this work, it was found that a composite composed of graphite oxide/cobalt/chitosan had strong stability and electron transfer capability and was applied to a bioelectrochemical nano-biosensor with high sensitivity and stability. As a mediator-modified electrode, the GO/Co/chitosan composite was electrically deposited onto an Au film electrode by covalent boding, while glucose oxidase as a receptor was immobilized on the end of the GO/Co/chitosan composite. It was confirmed that the electron transfer ability of the GO/Co/chitosan composite was excellent, as shown with power density analysis. In addition, the real-time detection of D-glucose could be successfully performed by the developed nano-biosensor with a high range of detected concentrations from 1.0 to 15.0 mM. Furthermore, the slope value composed of the current, per the concentration of D-glucose as a detection response, was significantly maintained even after 14 days.

Elderberry, which is well known for its richness in anthocyanin, is attracting attention in the bioindustry as a functional material with high antioxidant capacity. The aim of this study is to optimize extraction conditions to more effectively recover anthocyanins from elderberry. In a fundamental experiment to determine the suitable solvent, various GRAS reagents, such as acetone, ethanol, ethyl acetate, hexane, and isopropyl alcohol, were used, and total phenol and anthocyanin contents were detected as 9.0 mg/g-biomass and 5.1 mg/g-biomass, respectively, only in the extraction using ethanol. Therefore, ethanol was selected as the extraction solvent, and an experimental design was performed to derive a response surface model with temperature, time, and EtOH concentration as the main variables. The optimal conditions for maximal anthocyanin recovery were determined to be 20.0 °C, 15.0 min, and 40.9% ethanol, and the total anthocyanin content was 21.0 mg/g-biomass. In addition, the total phenol and flavonoid contents were detected as 67.4 mg/g-biomass and 43.8 mg/g-biomass, respectively. The very simple and economical extraction conditions suggested in this study contributed to improving the utilization potential of anthocyanin, a useful antioxidant derived from elderberry.

Peanut shells (PSs) generated from agricultural waste contain valuable compounds with bioactive properties such as anti-aging, antimicrobial, and antioxidant properties, making it desirable to recycle them as a sustainable resource. The aim of this study is to design an effective luteolin recovery process as the first step of an integrated biorefinery utilizing PSs as raw material. The major extraction variables and their ranges for luteolin recovery from PSs were determined (0–60 °C, 1–5 h, 0–100% MeOH concentration) and a predictive model was derived through a response surface methodology (RSM). Based on the predictive model, the equation determined for the maximal extraction of luteolin at 1 h was as follows: y = –1.8475x + 159.57, and the significant range of variables was as follows: 33.8 °C ≤ temperature (x) ≤ 48.5 °C and 70.0% ≤ MeOH concentration (y) ≤ 97.5%, respectively. High antioxidant and elastase inhibitory activities of PS extracts were confirmed, and these results support their potential to be used as functional materials. In addition, 39.2% of the solid residue after extraction was carbohydrate, which has potential as a carbon source for fermentation. This study provides a useful direction on an integrated biorefinery approach for sustainable agricultural waste valorization.

Alginate, a promising biopolymer in the food, biomedical, pharmaceutical, and electronic materials industries, is characterized by its biodegradability, biocompatibility, low toxicity, and gel-forming properties. It is most abundantly found in brown algae. However, conventional dilute acid and alkali extraction methods face limitations in commercialization due to their long processing time, low throughput, and high solvent requirements. In this study, a microwave-assisted extraction (MAE) process for sodium alginate was designed to improve extraction efficiency. The solid/liquid ratio, extraction temperature, and extraction solvent concentration were major variables affecting sodium alginate extraction from Undaria pinnatifida (sea mustard). They were then statistically optimized using response surface methodology. Under optimal conditions (13.27 g/L, 91.86 °C, 2.51% (w/v), and 15 min), the yield was 38.41%, which was 93.43% of the theoretical content of sodium alginate in Undaria pinnatifida. Our work has confirmed the productivity and industrial feasibility of the efficient extraction of sodium alginate from marine biomass, and we hope that it will serve as an encouraging case for the application of biopolymers as one of the desirable options for alternative petrochemicals to construct a sustainable society.

Mandarin peels (MPs), a food-processing residue, have several restrictions on their disposal and can cause serious environmental pollution. In this study, MP was used to fabricate a functional bioelastomer with antioxidant and antibacterial activities. Bioactive compounds were recovered from MPs in liquid form and added to the bioelastomer during fabrication to maintain the mechanical strength of the bioelastomer. The radical scavenging activities of the fabricated bioelastomer (B–MPE 15%) were 3.3% for DPPH and 20.8% for ABTS, respectively. In addition, B–MPE 15% exhibited antibacterial activity against gram-positive (Staphylococcus aureus), gram-negative (Escherichia coli), and antibiotic-resistant bacteria (Methicillin-resistant S. aureus and Vancomycin resistant Enterococcus). The chemical properties of B–MPE 15% were not significantly different from those of the control group (bare PDMS). Tensile strength, elongation at break, and water vapor transmission rate of B–MPE 15% were found to be 5.1 N/mm², 649%, and 33.3 g/(m² day), respectively. Therefore, the addition of MP extracts did not significantly affect the physical properties. The fabricated bioelastomer with antibacterial and antioxidant activities is expected to be utilized in the food packaging, pharmaceutical, and medical industries. Our research is expected to represent a future-oriented strategy for realizing carbon neutrality by upcycling food waste.

Haematococcus pluvialis is a microalgae actively studied for the production of natural astaxanthin, which is a powerful antioxidant for human application. However, it is economically disadvantageous for commercialization owing to the low productivity of astaxanthin. This study reports an effective screening strategy using the negative phototaxis of the H. pluvialis to attain the mutants having high astaxanthin production. A polydimethylsiloxane (PDMS)-based microfluidic device irradiated with a specific light was developed to efficiently figure out the phototactic response of H. pluvialis. The partial photosynthesis deficient (PP) mutant (negative control) showed a 0.78-fold decreased cellular response to blue light compared to the wild type, demonstrating the positive relationship between the photosynthetic efficiency and the phototaxis. Based on this relationship, the Haematococcus mutants showing photosensitivity to blue light were selected from the 10,000 random mutant libraries. The M1 strain attained from the phototaxis-based screening showed 1.17-fold improved growth rate and 1.26-fold increases in astaxanthin production (55.12 ± 4.12 mg g⁻¹) in the 100 L photo-bioreactor compared to the wild type. This study provides an effective selection tool for industrial application of the H. pluvialis with improved astaxanthin productivity.