Production of bio-sugar and bioethanol from coffee residue (CR) by acid-chlorite pretreatment

Enhancing the ethanol production by exploiting a novel metagenomic-derived bifunctional xylanase/β-glucosidase enzyme with improved β-glucosidase activity by a nanocellulose carrier

Some enzymes can catalyze more than one chemical conversion for which they are physiologically specialized. This secondary function, which is called underground, promiscuous, metabolism, or cross activity, is recognized as a valuable feature and has received much attention for developing new catalytic functions in industrial applications. In this study, a novel bifunctional xylanase/β-glucosidase metagenomic-derived enzyme, PersiBGLXyn1, with underground β-glucosidase activity was mined by in-silico screening. Then, the corresponding gene was cloned, expressed and purified. The PersiBGLXyn1 improved the degradation efficiency of organic solvent pretreated coffee residue waste (CRW), and subsequently the production of bioethanol during a separate enzymatic hydrolysis and fermentation (SHF) process. After characterization, the enzyme was immobilized on a nanocellulose (NC) carrier generated from sugar beet pulp (SBP), which remarkably improved the underground activity of the enzyme up to four-fold at 80°C and up to two-fold at pH 4.0 compared to the free one. The immobilized PersiBGLXyn1 demonstrated 12 to 13-fold rise in half-life at 70 and 80°C for its underground activity. The amount of reducing sugar produced from enzymatic saccharification of the CRW was also enhanced from 12.97 g/l to 19.69 g/l by immobilization of the enzyme. Bioethanol production was 29.31 g/l for free enzyme after 72 h fermentation, while the immobilized PersiBGLXyn1 showed 51.47 g/l production titre. Overall, this study presented a cost-effective in-silico metagenomic approach to identify novel bifunctional xylanase/β-glucosidase enzyme with underground β-glucosidase activity. It also demonstrated the improved efficacy of the underground activities of the bifunctional enzyme as a promising alternative for fermentable sugars production and subsequent value-added products.

Coffee residue as a valorization bio-agent for shelf-life extension of lactic acid bacteria under cryopreservation

The present work describes the feasibility of coffee residue extracts as cryoprotective agents in the storage stability of freeze-dried lactic acid bacteria. Coffee residue extracts were extracted from coffee residue, produced after coffee extraction for coffee powder and instant coffee preparation, using an autoclave. Leuconostoc mesenteroides WiKim32 was selected to evaluate the ability of coffee residue extracts to protect bacteria during freeze-dried storage. The storage stability of freeze-dried Leu. mesenteroides WiKim32 with coffee residue extracts was comparable to those with commercial cryoprotective agents. Coffee residue extracts contributed to storage stability immediately after freeze-drying (61.2%) and subsequent storage (48.7%). Our data indicate that the protective effect of the coffee residue extracts is associated with ions, carbohydrates, and phenolic compounds. Coffee residue extracts are feasible materials, which can reduce the storage and distribution costs compared to commercial agents currently available.

Biorefining Process of Carbohydrate Feedstock (Agricultural Onion Waste) to Acetic Acid

The biorefining of agricultural waste into green chemicals has clear potential for improving global environmental sustainability. In this study, we evaluated the potential of acetic acid production from carbohydrate feedstock (onion waste, OW) as a more environmentally friendly source than feedstock produced from natural gas. In particular, OW is an ideal feedstock for the biorefining process as it contains a sufficient amount of carbohydrates (69.7%). Five days of the simultaneous saccharification and two-step fermentation (SSTF) process produced acetic acid from OW more efficiently than the simultaneous saccharification and cofermentation (SSCF) process. SSTF produced 19.3 g/L acetic acid and recorded the highest conversion yield (90.5%) from OW (6% substrate loading, w/v). These results suggested that acetic acid can be efficiently and sustainably produced from OW by the SSTF process.

Advanced strategy to produce insecticidal destruxins from lignocellulosic biomass Miscanthus

BACKGROUND

Biorefineries are widely recognized as the most feasible solution to the problem of achieving environmental sustainability along with economic growth. Furthermore, pine wilt disease has caused severe environmental and economic damage worldwide to date. Herein, a highly efficient, advanced process for producing destruxins (DTXs) from Miscanthus (MCT) is reported, along with an application strategy.

RESULTS

The acetic acid-sodium chlorite pretreatment of MCT (AASC-MCT) is found to improve the monosaccharide production. Through biocatalytic conversion processes (simultaneous saccharification and cultivation), Metarhizium anisopliae JEF-279 can efficiently produce DTXs from 1% (w/v) AASC-MCT, i.e., DTX E (334.8 mg/L), A (288.8 mg/L), and B (48.6 mg/L). Monochamus alternatus (MA, Japanese pine sawyer) is known to act as a mediator transferring Bursaphelenchus xylophilus to pinewood. As B. xylophilus is associated with the occurrence of pine wilt disease, biological control of MA is a major strategy or controlling this disease. In this study, upon the application of a mixture of DTXs and protease-containing culture filtrate (PCF), complete mortality of MA is observed after a 5-day incubation. The MA immune system response is believed to cause an overexpression of actin and tropomyosin as a defense mechanism against the flaccid paralysis induced by the DTXs and PCF treatment.

CONCLUSIONS

These results suggest that MCT can be used as a major feedstock in the biorefinery industry and that DTXs can be applied as an insecticide for biological control of pine wilt disease via MA termination.

Radiofrequency heating for powder pasteurization of barley grass: antioxidant substances, sensory quality, microbial load and energy consumption

BACKGROUND

Young barley grass powder contains abundant nutrition and its antioxidant substances are severely impaired by radiation (⁶⁰ Co) sterilization. To overcome product quality degradation, radiofrequency pasteurization was conducted using pilot-scale radiofrequency equipment (27 MHz, 6 kW) with electrode gaps of 12, 14 and 16 cm, while hot-air (80 °C) pasteurization was used for comparison.

RESULTS

Assessment suggested that uneven radiofrequency heating was improved for the 14 cm electrode gap. With an increase of electrode gap, microbial inactivation needs more energy consumption. A minimum energy consumption of 970 J g^-1 was required for 1 log-reduction of colonies. Radiofrequency pasteurization retained better antioxidant substances, lightness (L*), green color (a*) and odors in barley grass powder, compared with hot-air sterilization. Contents of flavonoid and chlorophyll were 5.82 and 4.87 g kg^-1 respectively, using the 14 cm electrode gap. Additionally, radiofrequency pasteurization led to an improvement in sourness, bitterness and umami tastes.

CONCLUSIONS

Radiofrequency pasteurization would be a superior alternative for the pasteurization of barley grass powder. © 2019 Society of Chemical Industry.

Bioethanol from sugarcane bagasse: Focused on optimum of lignin content and reduction of enzyme addition

To investigate the effect of delignification on enzymatic saccharification and ethanol fermentation of sugarcane bagasse (SCB), NaClO, NaOH, and Na₂CO₃ were used to prepare SCB with different lignin contents. We found that a lignin content of approximately 11% was sufficient for enzymatic saccharification and fermentation. Based on this result, an economical delignification pretreatment method using a combination of acid and alkali (CAA) was applied. Lignin content of 11.7% was obtained after CAA pretreatment with 0.5% w/v H₂SO₄ at 140 °C for 10 min and 1.0% w/v NaOH at 90 °C for 60 min. Presaccharification-simultaneous saccharification and fermentation (P-SSF) of the CAA-pretreated SCB resulted in an ethanol concentration of 43.8 g/L and an ethanol yield of 81.7%, with an enzyme loading of 15 FPU/g-CAA-pretreated SCB. Enzyme activities (filter paper, carboxymethyl cellulase, and β-glucosidase activities) were determined in liquid phase during P-SSF, indicating that the residual cellulase activity could be further used. Thus, fed-batch P-SSF was carried out, and an ethanol concentration of 43.1 g/L and an ethanol yield of 80.4% were obtained with an enzyme loading of 10 FPU/g-CAA-pretreated SCB. Fed-batch P-SSF was found to be effective to reduce enzyme loading.

Comparison of ultrasound-assisted ionic liquid and alkaline pretreatment of Eucalyptus for enhancing enzymatic saccharification

Two ultrasound-assisted pretreatment technologies, ultrasound-assisted alkaline and ultrasound-assisted aqueous ionic liquid tetrabutylammonium hydroxide ([TBA][OH]), are compared systematically in regard to enzymatic saccharification. Pretreated Eucalyptus samples were characterized by powder X-ray diffraction, ¹³C cross polarization/magic-angle spinning solid state NMR spectroscopy, Fourier transform infrared spectroscopy, Scanning electron microscope (SEM) and chemistry composition analysis. These results not only explain the enzymatic saccharification difference between samples from the microstructure level, but also provide helpful information for relevant pretreatment research. Ultrasound-assisted [TBA][OH] pretreatment acquired a significant enhancement in the initial enzymatic rate of cellulose (79.39 mg/g/h), and a reducing sugar yield of 426.6 mg/g at 48 h. The pretreatment combining inexpensive aqueous ionic liquid and ultrasound may provide a promising strategy in the field of bio-refinery because of its unique advantages.