Search

Lignocellulosic biomass as a second-generation biofuel resource such as waste from agricultural, forester industry, and unutilized wood and non-wood biomass was widely reported to use it as feedstock for methane production. As the carbon-neutral resources, biomass waste conversion for biofuel is in line with the SDGs 7 and 15 goal that can meet the needs and qualify to the standard of sustainable consumption and production pattern, and increasing the renewable energy. The wood and non-wood unutilized biomass and biomass waste are commonly faced with the recalcitrant character of the lignocellulose complex (LCC) which impacted the digestion process of the methane fermentation. Steam explosion pretreatment was enhanced the methane production by breaking the LCC into cellulose, hemicellulose, and lignin-derived product generated from the pretreatment process. Those steam-exploded products were reported effective in the conversion process into methane. The combination of steam explosion pretreatment which is an environmentally friendly pretreatment, and the use of carbon-neutral resources will provide the green biofuel which helps decrease the greenhouse gasses from the biomass waste dumping process and convert it into sustainable biofuel i.e. methane. This chapter will describe the steam explosion system development on the utilization of biomass for methane production, and the action of methane production enhancement.

Steam treatment followed by milling treatment, an environmentally friendly method, was used and evaluated as a pretreatment of cedar for the preparation of cellulose nanofiber (CNF). The treated cedar was extracted with water followed by acetone and then received sodium chlorite (NaClO2) treatment, and separated into volatile component, water soluble component, acetone soluble component, NaClO2 soluble component, and NaClO2 insoluble component (a raw material of CNF preparation). The effects of steam pressures on the properties of treated cedar were examined from experimental data for the amounts of extracted components and the degree of polymerization. The properties of CNF obtained from cedar that was steam-treated at a steam pressure of 15 atm for a steaming time of 5 min and then milling-treated for 10 s were almost the same as those of commercial CNF (BiNFi-s). The reinforcing effect of CNF obtained in this treament condition was clarified, and the specific tensile strength and the specific Young’s modulus of PLA/CNF composite were 58.1 MPa/g/cm3 and 7.56 GPa/g/cm3 that corresponded to 1.6 and 3.1 times higher than those of PLA only, i.e. 33.0 MPa/g/cm3 and 2.44 GPa/g/cm3, respectively.

Low-molecular weight lignin was used as a curing agent to synthesize a bio-based cured epoxy resin. The low-molecular weight lignin was extracted from moso bamboo using steam treatment at 10–40 atm for 5 min followed by milling treatment for 10 s and then water and acetone extractions. The number and weight average molecular weight of low-molecular weight lignin, i.e. acetone soluble component, were 554–698 and 1460–3240, respectively. Furthermore, the hydroxyl equivalent of low-molecular weight lignin were 111–169 g-lignin/eq. The lignin-cured epoxy resin was made from EP828 (a commercial diglycidyl ether bisphenol A epoxy resin) with the low-molecular weight lignin as a curing agent. The decomposition temperature at 5% weight loss (Td5) of lignin-cured epoxy resins were 298–327 °C and the maximum value, i.e. 327 °C, was obtained using a low-molecular weight lignin at 30 atm. Though Td5 varied with the steam pressure, all values satisfied the thermal stability property required for soldering resistance in the electronic substrate field, i.e. beyond 250 °C. The tensile strengths of lignin-cured epoxy resins were 44–59 MPa and these values satisfied the tensile strength of commercial cured epoxy resins, i.e. beyond 27 MPa.

The antioxidant activity of water extract from bamboo by high-temperature and high-pressure steam treatment was analyzed. Bamboo was decomposed by high-temperature and high-pressure steam treatment, and more decomposition products were extracted with water extraction. The maximum antioxidant activity, i.e., EC50 = 0.127 mg/mL, and the maximum flavonoid content, i.e., 3.94 mg-quercetin equiv./g-dry weight bamboo, of water extract were obtained at a treatment pressure of 30 atm for a steaming time of 5 min. Compared with the untreated sample, they showed about 4.16 times higher of antioxidant activity and 6.02 times higher of flavonoid content. The maximum total polyphenol content, i.e., 35.7 mg-catechin equiv./g-dry weight bamboo, of water extract was obtained at 25 atm for 5 min. Compared with the untreated sample, it showed 6.69 times higher of total polyphenol content. The water extract from bamboo by high-temperature and high-pressure steam treatment was fractionated by high-performance liquid chromatography (HPLC). The structure of the fraction showing the highest antioxidant activity in the fractionated extract was determined. It had a structure having two highly reactive phenolic hydroxyl groups. The two phenolic hydroxyl groups reacted with reactive oxygen species (ROS) to cause a reduction reaction, thereby exhibiting antioxidant activity.

To investigate methane production from a single substrate with steam explosion pretreatment and activated cow dung as natural resources for cellulolytic microflora to enhance biogas production from agricultural biomass waste. The recalcitrant of the lignin-carbohydrate complex (LCC) of rice husk was dismounted using a steam explosion pretreatment at 2.53 MPa (224 °C) for 5 and 7 min of steaming time, followed with and without water extraction. All the residue from the extraction process, either solid or liquid, was used for the biogas feedstock. Anaerobic digestion (AD) was conducted under mesophilic condition at 37 °C with two different inoculums: sludge and a mixed inoculum containing sludge and activated cow dung. The predicted methane production was calculated using the stoichiometric formula. The steam explosion pretreatment and mixed inoculum significantly enhanced the cumulative methane production. The 7-min steaming time led to the breaking up of 41% cellulose, and 199 ml/g of methane was produced from the total cumulative methane yield of the solid and liquid feedstock, with a 96.1% yield of the predicted methane amount. The enhancement of methane production was achieved using a combination of steam explosion pretreatment and mixed inoculum between sludge and activated cow dung.

Hericium erinaceus has been widely used in food and medicine because of its various promising bioactivities. This study investigated the effects of Tween series surfactant and agar addition on mycelial growth and β-glucan in liquid submerged culture of the medicinal mushroom H. erinaceus. The addition of Tween 80 in liquid medium resulted in higher dry cell weight (DCW) and β-glucan production, with values of 6.06 and 1.21 g/L for 3.0% (w/v) and 7.27 and 1.22 g/L for 4.0% (w/v), respectively. This corresponded to a 1.82 relative ratio of DCW to control and a 1.86 relative ratio of β-glucan to control for 3.0% (w/v) and a 2.18 relative ratio of DCW to control and a 1.87 relative ratio of β-glucan to control for 4.0% (w/v), respectively. Further, the mycelial pellets were altered by the addition of agar in liquid medium, forming small pellets. The pellet diameter decreased with increasing medium viscosity, and the smallest pellet diameter, 1.5 mm, was attained with the addition of 0.3% (w/v) agar. The medium viscosity was 48.7 mPa s. Moreover, β-glucan production increased with a decreasing pellet diameter, and the highest β-glucan production, 0.86 g/L, was observed with 0.3% (w/v) agar added to the medium. The influence of flask type on DCW and β-glucan production was investigated which were almost 1.2-fold higher in baffled Erlenmeyer flasks than in normal Erlenmeyer flasks. Finally, cultivation with agar addition in a baffled Erlenmeyer flask was determined to be most effective for DCW and β-glucan production, yielding the highest values of 7.74 and 1.43 g/L, respectively.

The aim of this study was to produce a high yield of direct hydrolysis of glucose from a cotton towel and wheat straw by microwave-assisted (MW) treatment. To this effect, a freeze-thawing with 3% NaOH was added before MW treatment. Multiple MW parameters were tested. For the towel, the highest glucose yield of 42.4% based on freeze-thawing with 3% NaOH-treated sample was observed after MW treatment at 200 °C for 30 s with 2% sulfuric acid as a catalyst. This corresponded to a 44.4% yield based on the cellulose content of treated samples, which was 1.3-fold higher than that of samples treated only by MW at 200 °C for 7 min with 1% sulfuric acid as a catalyst (maximum glucose yield in our previous report). For wheat straw, the highest glucose yield of 27.0% based on freeze-thawing with 3% NaOH-treated sample, and 41.9% based on the treated sample cellulose content were observed after MW treatment at 200 °C for 3 min with 0.5% sulfuric acid as a catalyst. Under the optimum conditions, the glucose yield was 40.5% from raw towel and 14.7% from wheat straw. Combined severity parameter analysis revealed that the addition of freeze-thawing with NaOH before the MW treatment increased the glucose yield and reduced the severity of the treatment conditions. In conclusion, freeze-thawing using 3% NaOH before MW treatment is effective for the direct hydrolysis of glucose from towels and wheat straw.

Recently, plant biomass has been attracting attention due to global warming and the depletion of fossil fuels. Lignocellulosic biomass (i.e., wood, straw, and bagasse) is attracting attention as an abundant renewable resource that does not compete with the food resources. It is composed of cellulose, hemicellulose, and lignin and is a potential resource that can be converted into high-value-added substances, such as biofuels, raw materials for chemical products, and cellulose nanofibers. However, due to its complicated structure, an appropriate pretreatment method is required for developing its biorefinery process. Steam explosion is one of the simplest and environmentally friendly pretreatments to decompose lignin structure, which converts cellulose into low-molecular-weight lignin with high efficiency. It has received significant attention in the field of not only biofuel but also biochemical production. Steam explosion involves the hydrolysis of plant biomass under high-pressure steam and the sudden release of steam pressure induces a shear force on the plant biomass. Moreover, it is a green technology that does not use any chemicals. Thus, a steam explosion-based biorefinery system is highly effective for the utilization of lignocellulosic into useful materials, such as ethanol, methane gas, antioxidant material, epoxy resin, and cellulose nanofiber.

The aim of this study was to synthesize a bio-based cured epoxy resin using acetone-soluble lignin, a low-molecular-weight lignin, obtained from steam-exploded wheat straw. Wheat straw, an agricultural waste, was steam-exploded at a steam pressure of 2.5 MPa (225 °C) for a steaming time of 5 min, following which it was extracted first with water and then with acetone, to obtain low-molecular-weight lignin. Lignin epoxy resin was synthesized by the reaction of acetone-soluble lignin with epichlorohydrin and then cross-linked with two kinds of curing agents, acetone-soluble lignin or petroleum-derived phenol novolac, to obtain cured lignin epoxy resins. Furthermore, ligno-p-cresol epoxy resin was synthesized using lingo-p-cresol that is made of acetone-soluble lignin and p-cresol, to improve the thermal and mechanical properties of the cured epoxy resin, using ligno-p-cresol epoxy resin instead of lignin epoxy resin. The thermal decomposition temperatures at 5% weight loss and the tensile strength of all lignin-derived bio-based curing epoxy resins obtained in this study exceeded 250 °C and 27 MPa, respectively, which are required for application in the electronic substrate material field. The cured epoxy resin synthesized from EP828 (a commercial fossil resource-derived epoxy resin) and ligno-p-cresol increased 10% weight loss and tensile strength, compared to that synthesized from EP828 and acetone-soluble lignin. Additionally, its tensile strength was almost the same as that of the fossil resource-derived cured epoxy resin synthesized from EP828 and TD2131 (a commercial fossil resource-derived curing agent).

In order to develop the total utilization system that not only cellulose but also lignin contained in waste bamboo (Phyllostachys pubescens) can be converted into useful products, a pressurized microwave-assisted ethanol solvent (PMAES) treatment was examined for the effective extraction of polyphenols with antioxidant activity and the preparation of cellulose nanofiber (CNF). The antioxidant activity of extract was evaluated by measuring the DPPH radical scavenging activity and the reinforcing effect of CNF prepared was examined by measuring the tensile strength of the composite with polylactic acid (PLA). The maximum antioxidant activity, i.e., EC50 = 59.3 μg/mL, of extract was obtained from bamboo treated at 180 °C for 7 min with 50 v/v% ethanol. This value was 0.158 times that of untreated and water-extracted bamboo (the lower the EC50 value, the higher the antioxidant activity) indicating that PMAES treatment was effective for extracting antioxidants. In the same treatment condition, the maximum tensile strength, i.e., 91.8 MPa, of CNF and polylactic acid (PLA) composite with a ratio of 30 wt% CNF was obtained and this value corresponded to 13.9 times that of neat PLA and 2.39 times that of CNF/PLA composite with the same ratio of commercial CNF. PMAES treatment was an effective method for not only the extraction of antioxidants but also the preparation of CNF with a strong reinforcing effect.

In this study, we produced cellulose nanofiber (CNF) from moso bamboo using high-temperature and high-pressure steam treatment combined with the milling treatment. This pretreatment method can be considered as an environmentally friendly method because the treated product contains only wood-derived components and water that generally do not lead to significant corrosion problems and formation of neutralization sludge. The specific tensile strengths of CNF obtained in this work were almost the same values as that of a commercial CNF. Furthermore, an eco-refinery pulp was made of holocellulose and CNF those were obtained from moso bamboo by this pretreatment method and its mechanical strength was evaluated. By changing the steam treatment conditions, it is possible to produce eco-refinery pulp of various specific tensile strengths adapted to the application and purpose.

Direct hydrolysis of a towel to glucose was investigated using microwave-assisted (MW) treatment combined with impregnation in concentrated sulfuric acid (SA) solution (51 wt% for 30 min) before the MW treatment. The maximum glucose yield by direct hydrolysis of an untreated towel was 30.9%, obtained at a heating temperature of 200 °C for 2 min. The maximum total glucose yield (from both direct hydrolysis and enzymatic hydrolysis of treated residue) was 74.2%, attained at a microwave heating temperature of 180 °C for 3 min. This condition is milder than that of MW treatment without impregnation in concentrated SA (our previous study, heating temperature of 200 °C for 7 min required). As shown by XRD of the unimpregnated and impregnated towels (in 9 and 36 wt% SA solution), the crystallinity index value decreased with the increase in SA concentration. Finally, 22.4 g of ethanol could be produced using the supernatant (containing glucose) and the microwave-treated residue as a carbon source for Saccharomyces cerevisiae, with less fermentation inhibition. Thus, impregnation in concentrated SA before MW treatment is effective for the production of glucose from cellulosic material and has low energy input.

Pearl oyster (Pinctada fucata) shell is a marine byproduct. In this study, we focused on the extraction of functional peptides from pearl oyster shell protein hydrolysate. Pearl oyster shell protein was hydrolyzed using two types of proteases, Nucleicin and Orientase 22 BF. The hydrolysate by Orientase 22 BF (6 h of reaction time) exhibited the highest angiotensin I-converting enzyme (ACE) inhibitory activity (82.4%, at peptide concentration of 0.25 mg/mL) with 26.0% degree of protein hydrolysis. The crude hydrolysate was extracted with water and fractionated into two segments (named F1 and F2) by gel chromatography on a Sephadex G-25 column. After consecutive purification of F1 through high-performance liquid chromatography (HPLC) on an ODS column twice, a hexapeptide with the sequence Gly-Val-Gly-Ser-Pro-Tyr (MW: 578.7 Da) was identified based on its amino acid sequence and through LC–MS. The final purified peptide exhibited 5.82 μg/ml of IC50 value of ACE inhibitory activity. Furthermore, Lineweaver-Burk plots suggested that the purified peptide acts as a competitive inhibitor against ACE. The results of this study suggest that pearl oyster shell proteins can be new attractive raw materials for the production of functional foods against hypertension.

Hydrothermal treatment (HTT) as a pretreatment method for compost raw material has multiple benefits such as enhanced solubility of organic material, improved bioaugmentation, and reduced biohazard by killing harmful microorganisms. In this study, we pretreated food waste via HTT at 180 °C for 30 min to investigate its effect on food waste composting. HTT generated 8.98 mg/g-dry solid (g-ds) of 5-hydroxymethylfurfural and 4.32 mg/g-ds furfural. These furan compounds were completely decomposed in the early stage of composting, subsequently the organic matter in the food waste started to be degraded. The HTT-pretreated experiment demonstrated less organic matter degradation during composting as well as lower compost phytotoxicity compared to the non-HTT-pretreated experiment, where the conversion of carbon was 25.2% and the germination index value was 55%. HTT probably denatured part of the organic matter and making it more difficult to decompose, thereby preventing the rapid release of high concentrations of phytotoxic compounds such as organic acids and ammonium ions during composting. High-throughput microbial community analysis revealed that only Firmicutes appeared in the HTT-pretreated experiment, however, other bacterial groups also appeared in the non-HTT-pretreated experiment. This was possibly influenced by furan compounds and the changes of easily degradable organic matter to hardly degradable. Bacillus and Lysinibacillus were dominant in both composting experiments during vigorous organic matter degradation, suggesting that these bacterial groups were the main contributors to food waste composting. This study suggests that HTT is advantageous for the pretreatment of easily degradable food waste, as compost with less phytotoxicity was produced.

Tadeai (Awa-ai) is an indigo plant that is produced in large quantities in Tokushima prefecture, Japan. The leaves of Tadeai are used for dyeing (Ai-zome), but there is no use for the other parts, i.e. flowers, stems, leaves, and roots, most of which are discarded. In this study, we search for new ways to use Tadeai including parts other than the leaves and examined the antioxidant activity of water soluble extract from Tadeai. To extract antioxidants efficiently, processing was undertaken using a microwave irradiation device. The evaluation of Tadeai extract and its antioxidant activity was performed by measuring the amount of phenolic compounds by the Folin–Ciocalteu method and the DPPH radical scavenging activity test. Compared to the sample that was not subjected to microwave treatment, the amount of phenolic compounds was observed to be double, and the antioxidant activity eight times higher. The microwave treatment conditions that showed the best results are 200 ℃ and 1 min, and the evaluation indicated that the part that exhibits the best results is the root. Furthermore, the differences among Tadeai varieties were also examined. The best result was for the “Kojoko Akahana;” the root of the “Kojoko Akahana” exhibited the highest antioxidant effect. Its amount of phenolic compounds and EC50 value were 44.1 mg-catechin equiv./g-dry sample and 0.018 g/L, respectively. In this study, it was shown that the antioxidant activity of the parts other than the leaves is high, so it is expected that Tadeai waste will be effectively utilized as a raw material for producing antioxidants in the future.

A novel biomass pretreatment method, i.e. pressurized microwave hydrothermal treatment with inorganic salts, and the simultaneous saccharification and fermentation (SSF) using salt-tolerant cellulase, i.e. Meicelase, and salt-tolerant yeast, i.e. Saccharomyces cerevisiae BA11, were studied for the efficient ethanol production from sugarcane bagasse. The component analysis, enzymatic saccharification, and alcohol fermentation were carried out using pressurized microwave treated sugarcane bagasse with various inorganic salts. The pressurized microwave treatment using 2 wt% MgCl2 at a treatment temperature of 200 °C for a treatment time of 5 min followed by SSF without washing treatment of inorganic salts provided the maximum glucose and ethanol yields, i.e. 0.392 and 0.18 g/g-raw material, those corresponded to 99 and 90% of saccharification and ethanol conversion ratios, respectively.

Microwave (MW)-assisted acid hydrolysis of lignocellulosic material derived from bode (Styrax tonkinensis) wood to glucose was performed to find effective uses for discarded chopsticks. The maximum amount of glucose produced by MW-assisted acid hydrolysis (from 1 g of untreated bode wood cellulose) was 0.48 g, and was obtained by heating at 200 °C for 1 min using 1.0% (w/w) sulfuric acid as catalyst. However, the maximum total glucose yield from both MW-assisted acid hydrolysis (0.16 g) and enzymatic hydrolysis of the treated residue (0.52 g) was 0.68 g, which was obtained at a microwave heating temperature of 180 °C for 5 min using 1.0% (w/w) sulfuric acid as catalyst. In conclusion, the results showed that microwave-assisted treatment at 200 °C using 1.0% (w/w) sulfuric acid as catalyst facilitated MW-assisted acid hydrolysis of bode wood cellulose and treatment at 180 °C served as pretreatment for enzymatic hydrolysis of the treated residue.

Holocellulose was generated from Aspen and Bode chopsticks by high temperature, high pressure steam treatment combined with milling. The steam treatment conditions were increased, the holocellulose component ratio in the treated sample as well as its molecular weight decreased. The treated holocellulose was subjected to grinder treatment to obtain cellulose nanofibers (CNF). Field-emission scanning electron micrographs indicated that CNF were successfully produced. The maximum tensile strength values of 86.9 and 109.9 MPa/(g/cm3) for Aspen and Bode, respectively, were obtained at a steam pressure of 15 atm and steaming time of 5 min. Furthermore, it was demonstrated that the optimal molecular weight of holocellulose to produce CNF with high tensile strength was around 1.2 × 105, while the optimal holocellulose recovery rate (HR; the degree of fibrillation was defined as HR in this study) was around 1.00.

Extraction of water soluble antioxidant materials from garlic husk (GH) was investigated using two hydrothermal methods, steam explosion (SE, 200 and 213 °C for 5 min) and microwave irradiation method (MW, 180 and 200 °C for 2 and 5 min). Water extract was evaluated by EC50 value (a concentration at a radical scavenging activity of 50%) and amount of phenolic compounds (expressed as catechin equivalent). Compared with the EC50 value (12.73 g/l) and amount of phenolic compounds (1.9 mg-catechin equiv./g-dry treated GH) of extract obtained from treated GH by conventional heating method using autoclave (121 °C for 10 min) combined with milling, the EC50 value decreased (increased the radical scavenging activity) and the amount of phenolic compounds increased dramatically with the extract obtained from treated GH by SE and MW, respectively. The lowest EC50 value (0.26 g/l) and the highest amount of phenolic compounds (40.0 mg-catechin equiv./g-dry treated GH) were attained by MW at treatment temperature of 200 °C for 5 min. Furthermore, relationship of EC50 value of extract obtained from treated GH by SE and MW and severity factor of each treatment condition indicated that appropriate severity factor to extract antioxidant material from GH highly using two hydrothermal methods, i.e. SE and MW could be around 3.0.

Lignocellulosic waste, i.e. wood, straw, and bamboo, represents abundant carbon-neutral renewable resources that are used to produce biofuels and biomaterials. Increased use of these resources would lower environmental impacts such as the emission of greenhouse gases (e.g. carbon dioxide) and fossil fuel depletion, helping to create a sustainable environment. Advances in technologies such as genetics, biotechnology, process chemistry, and engineering are leading to the concept of biorefining. In order to develop a method for the total biorefinery processing of lignocellulosic waste, this study focused on the efficient separation and utilization of woody structural components from white poplar chopstick waste by using a steam explosion pretreatment followed by water and acetone extractions. The cellulose component was converted into cellulose nanofiber (CNF) and the lignin component was used as a raw material for the synthesis of epoxy resin. The components of the steam-exploded product were extracted and separated into water extract, acetone extract, and holocellulose. The water extract had a high catechin equivalent and the cured epoxy resin was synthesized from acetone extracted as a raw material. Furthermore, the study confirmed the significant reinforcement effect of CNF, obtained from the holocellulose, on polylactic acid. The steam explosion, extraction, and separation methods, along with various conversion processes proposed in this study, appear to be some of the most efficient and environmentally friendly (i.e. generating few pollutants) conversion methods of lignocellulosic waste into eco-materials, i.e. CNF, cured lignin epoxy resin, etc.

Direct hydrolysis of a towel to glucose was investigated using steam explosion and microwave-assisted treatment to find effective uses for cotton waste. The maximum glucose yield by direct hydrolysis (based on an untreated towel) was 18.8%, obtained at a steam pressure of 5.5 MPa (at 271 °C) and steaming time of 5 min using steam explosion. For the microwave-assisted treatment, with a 1.0 (w/w)% sulfuric acid catalyst, the maximum glucose yield by direct hydrolysis was 28.9%, obtained at a microwave heating temperature of 200 °C for 7 min. The maximum total glucose yield (from both direct hydrolysis and enzymatic hydrolysis of treated residue) was 78.0%, attained at a microwave heating temperature of 200 °C for 7 min with 0.5 (w/w)% sulfuric acid catalyst. Furthermore, the maximum total glucose and valuable water soluble chemicals (cellobiose, 5-hydroxymethylfurfural, formic acid, and levulinic acid), 94.1%, were achieved at heating temperature of 200 °C for 10 min with 0.5 (w/w)% sulfuric acid catalyst. Finally, ethanol, 84.5% of conversion rate, could be produced using supernatant (it contained glucose) and microwave treated residue (200 °C for 7 min with 0.25 (w/w)% sulfuric acid catalyst) as carbon source for Saccharomyces cerevisiae with less fermentation inhibition.

Steam explosion pretreatment with high steam pressures, i.e. 35–55 atm, was conducted for the effective conversion of mixed softwood sawdust waste into ethanol. The results show the steam explosion with high steam pressures can significantly enhance the glucose yield after enzymatic saccharification and ethanol yield after alcohol fermentation. The effects of steam pressure on physical and chemical characteristics of steam-exploded sawdust were also clarified. Avoiding the effect of inhibitory materials produced by steam explosion with high pressures on enzymatic saccharification and alcohol fermentation, water and methanol extractions were attempted. The residue after water and methanol extractions of steam-exploded sawdust at a steam pressure 45 atm for a steaming time of 5 min was the most effective for the enzymatic saccharification followed by alcohol fermentation, and obtained a highest glucose yield, i.e. 81%. Simultaneous saccharification and fermentation using a high concentration of the residue resulted in an increased ethanol concentration and provided an ethanol production, i.e. 46.0 and 66.7 g/L, and a volumetric productivity of ethanol, i.e. 0.64 and 0.92 g/L h, from 200 to 300 g/L residue, respectively.

In order to reduce the amount of choline acetate ([Cho][OAc]), (a less expensive, more biodegradable and biocompatible ionic liquids) used in the pretreatment of sugarcane bagasse, [Cho][OAc] combined with organic solvents pretreatments were attempted. The glucose yields after a 72-h enzymatic saccharification of sugarcane bagasse pretreated with [Cho][OAc] combined with organic cosolvents dimethyl sulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), or ethylene glycol (EG) at a weight ratio of 1:1 keeping at 130 °C for 180 min were approximately equal to those from the bagasse treated with [Cho][OAc] alone. The result indicated that the combination use of the cosolvents made it possible to reduce 50% of amount used of [Cho][OAc]. The enhancement effect of the [Cho][OAc]/cosolvent pretreatment on enzymatic saccharification could be attributed to an equal or greater effect on removal of hemicelluloes and lignin compared to the [Cho][OAc] treatment alone, although a lower effect on reduction in cellulose: which was supported by componential and X-ray diffraction (XRD) analyses. The bagasse pretreated with [Cho][OAc]/DMSO (1:1 w/w) used in simultaneous saccharification and fermentation using Saccharomyces cerevisiae BA11, and ethanol was produced with a corresponding to conversion ratio of 69.9%.

The active ingredients of Japanese green tea (Camellia sinensis) were utilized to synthesize bio-based epoxy resin. The catechin compounds in the aqueous extract of green tea were functionalized with epichlorohydrin under alkaline conditions in the presence of tetramethylammonium chloride (TMAC), a water soluble phase transfer catalyst. A good yield of resin was synthesized, and curing was performed with methanol soluble lignin extracted from eucalyptus. The epoxy networks, so synthesized, were compared with bisphenol-A (BPA)-derived epoxy network. The thermal and mechanical properties of the bio-based resin were assessed through thermogravimetric, flexural strength, and glass transition (Tg) analyses. Catechin-based epoxy networks were found to exhibit good thermal and mechanical properties, rendering them potential BPA substitutes. The thermal decomposition temperature resulting in 5% weight loss (Td5) of synthesized epoxy resin was found to be above 300 °C, which is slightly lower than that of BPA-derived epoxy resin. The synthesized bio-based resins meet the requirement for the dip-shoulder resistant temperature (250–280 °C), with Tg values ranging from 155 to 178 °C, highlighting their potential use as one of the most suitable BPA substituents as well as their use in electronic materials.

In this study, ionic liquid (IL) pretreatment using choline acetate ([Cho][OAc]), which is a completely bioderived IL, for enhancing the enzymatic saccharification of lignocellulose was investigated. To evaluate [Cho][OAc] IL pretreatment, its effects on sugarcane bagasse composition, its subsequent enzymatic saccharification, and the energy profit ratio (EPR) were compared with those of various pretreatments, such as comminution, microwave irradiation, and alkaline treatment. After 72 h of enzymatic saccharification using bagasse pretreated with [Cho][OAc] at 110 °C for 360 min, 0.355 g of glucose per 1 g of raw bagasse was obtained (i.e., 98.7% of the cellulose content of the pretreated bagasse was converted into glucose), and maximum EPR was achieved in these pretreatment conditions.

In recent years, in order to reduce the environmental burden of composite materials, research has been conducted to develop composites made from plant-derived polymers and natural fibers, the so called green composites. In this study, green composites were made from polylactic acid (PLA), a bioplastic derived from corn starch, reinforced with bamboo fibers. The composites were manufactured by mixing short bamboo fibers and dispersion-type PLA resin. Subsequently, PLA/bamboo fiber sheets were molded by a hot pressing method. In order to improve the adhesion at the matrix/fiber interface and to obtain uniformly dispersed bamboo fibers in PLA matrix, the bamboo fibers were treated by alkali solution. It was found that the composites reinforced by alkali-treated bamboo fibers have higher strength than those based on untreated ones. Bamboo fibers were uniformly dispersed in PLA matrix with improved interfacial adhesion as lignin in bamboo fibers were removed by the alkali treatment. It was concluded that alkali treatment was an effective method for improvement of interfacial matrix/fiber adhesion in PLA/bamboo fiber-reinforced green composites.

A low molecular weight lignin from various lignocellulosic materials was used for the synthesis of bio-based epoxy resins. The lignin extracted with methanol from steam-exploded samples (steaming time of 5 min at steam pressure of 3.5 MPa) from different biomasses (i.e., cedar, eucalyptus, and bamboo) were functionalized by the reaction with epichlorohydrin, catalyzed by a water-soluble phase transfer catalyst tetramethylammonium chloride, which was further reacted with 30 wt% aqueous NaOH for ring closure using methyl ethyl ketone as a solvent. The glycidylated products of the lignin with good yields were cured to epoxy polymer networks with bio-based curing agents i.e., lignin itself and a commercial curing agent TD2131. Relatively good thermal properties of the bio-based epoxy network was obtained and thermal decomposition temperature at 5% weight loss (Td5) of cedar-derived epoxy resin was higher than that derived from eucalyptus and bamboo. The bio-based resin satisfies the stability requirement of epoxy resin applicable for electric circuit boards. The methanol-insoluble residues were enzymatically hydrolyzed to produce glucose. This study indicated that the biomass-derived methanol-soluble lignin may be a promising candidate to be used as a substitute for petroleum-based epoxy resin derived from bisphenol A, while insoluble residues may be processed to give a bioethanol precursor i.e., glucose.

In this study, we investigated the simultaneous saccharification, fermentation and detoxification SSDF process of steam-exploded cedar using a detoxification microorganism, Ureibacillus thermosphaericus A1, to facilitate efficient ethanol production. Steam explosion was applied as a pretreatment before enzymatic saccharification followed by alcohol fermentation. The highest glucose conversion rate was observed in the sample pretreated with a steam pressure of 45atm for 5min. Alcohol production by a heat-tolerant yeast, Saccharomyces cerevisiae BA11, was inhibited strongly by inhibitory materials present in the steam-exploded cedar, such as formic acid, furfural, and 5-hydroxymethylfurfural. The maximum amount of ethanol, i.e., 0.155g ethanol/g dry steam-exploded cedar, which corresponded to 74% of the theoretical ethanol yield, was obtained using the SSDF when U. thermosphaericus A1 degraded the inhibitory materials. A fed batch SSDF culture, in which U. thermosphaericus A1 was used to maintain low concentrations of inhibitory materials, was effective for increasing the ethanol concentration.

Discarded branch prunings from Japanese pear trees (Pyrus pyrifolia cv. Kousui) are promising resources containing polysaccharides and polyphenols. This study aimed at the total utilization of discarded branches. Arbutin is an inhibitor of biosynthesis of the human pigment melanin and extensively used as a human skin-whitening agent. It was found that most of the arbutin in the branches was contained in the bark (27.1 mg/g dry matter) compared with that in wood (5.2 mg/g dry matter). We evaluated the effect of the extracted solution containing arbutin (ESCA) from the bark on melanin formation in B16 melanoma cells. At a concentration of 4.0 × 10−3 % of ESCA, treated B16 melanoma cells showed 77.9 ± 3.9 % of the melanin production of untreated cells, with no cytotoxicity. The residue (wood) after arbutin extraction contained abundant holocellulose (69.8 %), and was accordingly hydrolyzed with cellulase and then converted into ethanol by Saccharomyces cerevisiae BA11, after microwave irradiation pretreatment. In total, 0.79 g of arbutin and 8.84 g of ethanol were produced from the 100 g of dry branches.

We investigated the production of acetone–butanol–ethanol (ABE) from acorns (starchy material) and wood chips (cellulosic material) of Quercus acutissima through separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) by Clostridium acetobutylicum NBRC13948. With acorns, 15.45 g/L of ABE was obtained in 96 h of fermentation time from the enzymatic hydrolyzate of acorns by SHF. From the SSF, it was found that ABE (16.70 g/L, 120 h) was produced without enzyme addition, given that C. acetobutylicum NBRC 13948 possesses an amylolytic enzyme. With wood chips, steam explosion was used for pretreatment. In the SHF, when the enzymatic hydrolyzate of residue of water and methanol extraction after pretreatment was used as the substrate, the maximum ABE concentration, 15.29 g/L, was obtained in 120 h. From the SSF, 13.41 g/L of ABE was obtained in 144 h, and it was determined that sufficient enzyme loading was 7.8 mg of protein to 1 g of dry substrate.

This study investigated the production of ethanol from unutilized branches pruned from pear trees by steam explosion pretreatment. Steam pressures of 25, 35, and 45 atm were applied for 5 min, followed by enzymatic saccharification of the extracted residues with cellulase (Cellic CTec2). High glucose recoveries, of 93.3, 99.7, and 87.1%, of the total sugar derived from the cellulose were obtained from water- and methanol-extracted residues after steam explosion at 25, 35, and 45 atm, respectively. These values corresponded to 34.9, 34.3, and 27.1 g of glucose per 100 g of dry steam-exploded branches. Simultaneous saccharification and fermentation experiments were done on water-extracted residues and water- and methanol-extracted residues by Kluyveromyces marxianus NBRC 1777. An overall highest theoretical ethanol yield of 76% of the total sugar derived from cellulose was achieved when 100 g/L of water- and methanol-washed residues from 35 atm-exploded pear branches was used as substrate.

Lignin extracted from steam-exploded bamboo has been used as resource material for the production of cured epoxy resins. In this study, 3 types of cured epoxy resin were prepared. The bamboo lignin extracted with methanol from steam-exploded bamboo (steam pressure 35 atm; steaming time 5 min) was epoxidized with epichlorohydrin and then cured with the general curing agent 1-(2-cyanoethyl)-2-ethyl-4-methylimidazole (2E4MZ-CN) and bamboo lignin. General epoxy resin, cured with diglycidyl ether bisphenol A (DGEBA) and 2E4MZ-CN, was simultaneously synthesized as a petroleum-derived epoxy resin control. The mechanical and thermal properties of lignin-based epoxy resins were compared with petroleum epoxy resins. As indicated by their thermal decomposition properties (Td5), the lignin-based epoxy resins exceeded the dip-solder resistance (250–280 °C). Furthermore, lignin-based epoxy resin showed 70% of the flexural strength of the petroleum-based epoxy resin.

Novel extraction method for increasing the antioxidant activity of raw garlic was proposed using steam explosion. Raw garlic was hydrolyzed by high temperature (183–258 °C) and pressure steam (10–45 atm), and then crushed by the rapid decompression. The antioxidant activity of raw garlic treated by steam explosion was higher than that of black garlic, i.e. aging garlic. The lowest EC50 value, i.e. the highest antioxidant activity, of extract from raw garlic was obtained at a steam pressure of 45 atm for a steaming time of 5 min, but the highest amount of phenolic compounds, i.e. 93.7 mg-catechin equiv./g-dry raw garlic, was obtained at a steam pressure of 30 atm for a steaming time of 5 min.

To utilize starch and protein contained in microalgae as carbon and nitrogen sources for ethanol production, an extrac- tion method, i.e. ultrasonic treatment using a homogenizer, and simultaneous saccharification and fermentation (SSF) of extracted microalgae solution were studied using Chlamydomonas fasciata Ettl 437. 30 min of ultrasonic treatment gave the maximum extraction ratio of starch contained in microalgae, i.e. 93.8%, that corresponded to 0.408 g-starch/g-dry microalgae. SSF of the extracted solution obtained from ultrasonic treated microalgae at 30 min by glutase-AN and Saccahromyces cerevisiae AM12 provided 0.194 and 0.168 g-ethanol/g-dry microalgae with and without yeast extract, respectively, corresponding to 79.5 and 68.8% of theoretical ethanol yield.

This study investigated the production of d-lactic acid from unutilized sugarcane bagasse using steam explosion pretreatment. The optimal steam pressure for a steaming time of 5 min was determined. The steam-exploded sugarcane bagasse was hydrolyzed using cellulase (Meicelase) and then the hydrolyzate was subjected to fermentation substrate. By enzymatic saccharification using Meicelase, the highest recovery of glucose from raw bagasse, 73.7 %, was obtained at a steam pressure of 20 atm. For extracted residue with water after steam explosion, the glucose recovery increased up to 94.9 % at a steam pressure of 20 atm. These results showed that washing with water is effective in removing enzymatic reaction inhibitors. After steam pretreatment (steam pressure of 20 atm), d-lactic acid was produced by Lactobacillus delbrueckii NBRC 3534 from the enzymatic hydrolyzate of steam-exploded bagasse and washed residue. The conversion rate of d-lactic acid obtained from the glucose concentration was 66.6 % for the hydrolyzate of steam-exploded bagasse without washing with water and 90.0 % for that derived from the extracted residue with water after steam explosion. These results also demonstrated that the hydrolyzate of steam-exploded bagasse (without washing with water) contains fermentation inhibitors and washing with water can remove them.

Buckwheat tea waste (BWTW) and barley tea waste (BTW), by-products of the beverage industry, are alternative carbohydrate sources for ethanol production. In this study, optimal enzyme loading for enzymatic saccharification of BWTW and BTW was determined, and simultaneous saccharification and fermentation (SSF) was performed by Saccharomyces cerevisiae and Mucor indicus to produce ethanol. Optimal enzyme loading for enzymatic saccharification of 2 % w/v BWTW and BTW was 0.5 % (weight of enzyme/weight of tea wastes) for BWTW and 0.1 % for BTW. Ethanol production from BWTW by S. cerevisiae and M. indicus after 48 h of SSF was 49.9/100 g of BWTW and 47.9/100 g of BWTW, respectively, with 0.5 % enzyme loading. Ethanol production from BTW by S. cerevisiae and M. indicus after 48 h of SSF was 20.5/100 g of BTW and 21.6/100 g of BTW, corresponding to 62 and 66 % of the theoretical yield based on starch content, respectively, with 0.1 % of enzyme loading. Furthermore, S. cerevisiae produced 76 % of the theoretical yield based on the total glucose from starch in BWTW and BTW when a mixture of BWTW and BTW was used as a substrate, with 0.2 % enzyme loading and no additional nitrogen or mineral sources.

Hydrolysis of two cellulosic materials, i.e. microcrystalline cellulose powder (MC) and cuprammonium rayon fiber (BEMCOT), to glucose was carried out by steam explosion treatment with ultra-high temperature and pressure steam aiming at an effective usage of unutilized cellulosic materials. 50 g of cellulosic materials were charged in a sealed reactor (2L) of the steam explosion apparatus kept at steam pressures of 50, 55, 60, and 62 atm for a steaming time of 1 min. The maximum yield of water soluble sugars, 52.8%, was obtained at a steam pressure of 62 atm and a steaming time of 1 min for MC. Furthermore, the maximum yield of water soluble sugars, 67.7%, was obtained at a steam pressure of 60 atm and a steaming time of 1 min for BEMCOT. This water soluble sugars contained 63.1% and 61.0% of glucose, respectively; they are corresponding to 33.3g and 41.0 g of glucose contained in 100g of dry steam-exploded cellulosic material.

For the bioremediation of pollutants in seawater, the degradation of phenol using novel marine bacteria isolated from the intestinal contents of marine creatures was investigated. Twenty samples of marine creatures were collected, and bacteria in their intestinal contents were incubated in an artificial seawater agar medium containing phenol. Two colonies (EBR01 and EBR02) were observed from Dendrodoris fumata , and one colony (EBR04) was observed from Suggrundus meerdervoortii . Analysis of the bacterial properties, gene sequencing, similarities, and phylogenetic characteristics showed that strains EBR01 and EBR02 were Acinetobacter species and strain EBR04 was Cobetia marina . Acinetobacter spp. EBR01, EBR02, and C. marina EBR04 degraded almost 100 mg l −1 phenol in seawater. The maximum phenol degradation rate using Acinetobacter sp. EBR01 was the highest value, and it was 2.7-fold higher than that using activated sludge.

Waste Shiitake (Lentinula edodes) mushroom medium, a lignocellulosic aglicultural residue, was evaluated as a fermentable substrate. 87% of the fermentable sugars remained in the waste mushroom medium. The sugar yield of the waste mushroom medium (46.3%) was higher than that of raw mushroom medium (20.3%) after 48 h of enzymatic saccharification by Meicelase because L. edodes changed wood structure. These results indicated that the waste mushroom medium is a suitable substrate for fermentation. Next, the efficient ethanol production using steam explosion pretreatment was studied. After 30 h of simultaneous saccharification and fermentation (SSF) using Meicelase and Saccharomyces cerevisiae AM12, 20.0 g/L ethanol was produced from 100 g/L water-insoluble residue of the waste mushroom medium treated at a steam pressure of 20 atm and a steaming time of 5 min. This corresponded to an ethanol yield of 77.0% of the theoretical, i.e. 14.7 g of ethanol obtained from 100 g of waste mushroom medium.

Basidiomycetes has recently attracted considerable attention for its various physiological activities, such as antitumor, antioxidant and immunostimulating activities. Compounds isolated from fruit body of Hericium erinaceum, commonly called Yamabushitake in Japan, have interesting biological activities such as cytotoxic effectors on cancer cell ( HeLa cells) and stimulators of synthesis of nerve growth factor. It is necessary for the cultivation of the fruit body of mushroom to control light, temperature, humidity. Otherwise, mycelia cultivation needs only temperature control. H. erinaceum cultivated by submerged culture have similar physiological activities to the fruit body of H. erinaceum, which suggests cultured mycelia can potentially become a promoter of synthesis of nerve growth factor. In this study, we used whey which is by-products of cheese-making process as an alternative nitrogen source in submerged cultivation of H. erinaceum mycelia, and then dry cell weight (DCW) and DCW productivity of whey medium were compared with those of chemical nutrient medium. When whey was used as a nitrogen source, DCW and DCW productivity are 1.5 times higher than those of chemical nutrient medium, 5.99 g/L and 0.60 g/L/day, respectively. It was suggested that whey could be used as an alternative nitrogen source and a growth promoting factor in H. erinaceum mycelia cultivation.

The effects of various carbon sources and their initial concentrations on mycelia production by Hericium erinaceum were investigated by determining the dry cell weight (DCW) and β-glucan content of mycelia in submerged culture. Glucose and xylose were superior carbon sources for promoting mycelial growth resulting in mycelial concentrations of 3.99 g/L and 4.01 g/L, respectively; glucose was the best carbon source in terms of productivity (0.44 g/L/day). Experiments were also performed using yogurt whey as an alternative nitrogen source for submerged cultivation of H. erinaceum mycelia, and DCW and β-glucan content were compared with those with chemical nutrient medium. When whey was used as a nitrogen source, DCW and total amount of β-glucan were 2.3- and 2.8-fold higher, respectively, than that with chemical nutrient medium. Thus, whey appears to be an alternative nitrogen source for promoting H. erinaceum mycelial growth.

Effective utilization process of not only cellulose but also lignin contained in softwood biomass into useful fuel and materials was developed using steam explosion with ultra-high temperature and pressure steam, extraction and various conversion methods. The conversion of softwood biomass into useful materials was studied for the effective utilization of its components such as cellulose, water soluble material, methanol soluble lignin, and Klason lignin. The cellulose, water soluble material, methanol soluble lignin, and Klason lignin were converted into useful fuel and materials, i.e. ethanol, antioxidant material, lignin epoxy resin, and activated carbon, respectively. 49.6 g of glucose or 17.4 g of ethanol was obtained from 100 g of steam-exploded product treated at a steam pressure of 45 atm and 3 min. Water soluble material had a comparatively high antioxidant activity and methanol soluble lignin was converted into a cured epoxy resin with heat-resisting property for solder demanded in the electronic material field.

Spent Shiitake mushroom medium was subjected to steam explosion followed by simultaneous saccharification and fermentation (SSF) using Meicelase and Saccahromyces cerevisiae AM12. Water extraction of the medium exposed to steam at 20 atm for 5 min enhanced the saccharification rate by about 20% compared to steam-exploded medium before water extraction and resulted in the production of 23.8 g/l ethanol from a substrate concentration of 100g/l. This corresponded to 87.6% of the theoretical ethanol yield, i.e., 15.9 g ethanol was obtained from 100g of spent Shiitake mushroom medium. Spent Shiitake mushroom medium subjected to steam explosion and then water extraction appears to be a candidate for efficient bioconversion to ethanol.

To convert waste disposable wooden chopsticks, cellulosic waste biomass, into ethanol efficiently, the effectiveness of pretreatments, i.e. ball-milling and steam explosion, for the enzymatic hydrolysis of aspen chopsticks and the dependence of substrate concentration using pretreated aspen chopsticks for the ethanol production were studied. In the enzymatic saccharification of ball-milled chopsticks, the maximum amount of glucose, 520 mg-glucoce/g-dry aspen chopsticks, was obtained from the chopsticks ball-milled for 60 min. On the other hand, the maximum amount of glucose, 598 mg-glucoce/g-dry aspen chopsticks, was obtained using steam-exploded aspen chopsticks treated at a steam pressure of 25 atm and a steaming time of 5 min. Simultaneous saccharification and fermentation (SSF) of the steam-exploded chopsticks by Meicelase and Saccahromyces cerevisiae AM12 provided 241 mg-ethanol/g-dry aspen chopsticks, corresponding to 79% of theoretical ethanol yield.

In order to examine the structure–activity relationship and the substrate specificity of human d -amino acid oxidase (h.DAO), a single amino acid mutation had been established as proline-219-luecine (P-219-L). The gene encoding mutant h.DAO has been cloned and expressed in Escherichia coli BL21 (DE3). It was observed that the host cell was negatively affected by the expressed mutant h.DAO, resulting in a remarkable decrease in the cell growth and consequently the amount of the produced enzyme. To overcome this problem, we investigated several factors that may affect the cell growth rate and the mutant h.DAO production such as optimization of the glucose concentration as a main carbon source and the yeast extract concentration as a main nitrogen source, optimization of dissolved oxygen (DO%) concentration and the addition of benzyl alcohol (BA, which can artificially induce a strong heat shock response at low temperature), to enhance the production of natively folded soluble fraction of the recombinant protein. These parameters were tested on both shake flask level and fed-batch bioreactor level. The Western blot analysis and the enzyme activity assay indicated the higher level of the mutant expression towards enhancement of the conditions by using our designed approach. The specific activity (which was used as an indicator for the level of the desired protein produced = U/mg protein) and the OD 600 nm of the host cells (which was used as an indicator for the cell growth), reached to be 0.061 U/mg protein and 3.44, respectively upon using fed-batch culture system containing the optimized medium composition (15 g/l glucose and 5 g/l yeast extract). While upon using the shake flask level, these values were 0.032 and 1.1, respectively. Enhancement of the cell growth and the enzyme production was noticed after DO% optimization upon using 500 rpm agitation speed and 1.8 v.v.m. (volume volume minute) aeration. The specific activity for the mutant enzyme and the OD 600 nm of the host cells reached to be 0.14 U/mg protein and 7.1, respectively. Finally upon using the optimized culture composition (15 g/l glucose and 5 g/l yeast extract), optimized DO% (using 500 rpm agitation speed and 1.8 v.v.m.) and 0.1 mM BA at the fed-batch bioreactor level, the specific activity and the OD 600 nm of the host cells increased significantly to be 0.21 U/mg protein and 11.3, respectively at 24 h culture. These results indicate the importance of our approaches to overproducing mutant h.DAO in soluble form in E. coli .