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The aim of this study is to optimize Organosolv pretreatment parameters for efficient lignin removal and polysaccharide release using response surface methodology based on central composite design. Organosolv pretreatment conditions (60–100 °C, 10–50 min and 50–90% acid concentration) were tested for maximum cellulose release and lignin solubilization and minimum hemicellulose decomposition. The optimum Organosolv pretreatment condition was achieved at an acid concentration of 69.85%, pretreatment time 29.68 min and pretreatment temperature of 75.41 °C. At optimal condition, 73.17% of lignin and 46.62% hemicellulose were solubilized, and 74.09% of cellulose was released. The high R squared and adjusted R squared values of 0.9801 and 0.9622 for lignin removal, 0.9831 and 0.9695 for cellulose released and 0.9851 and 0.9717 for hemicellulose solubilization shows that the quadratic models are adequate and the experimental data adequately fitted to the design model. Moreover, all the process parameters: temperature, time and concentration have a significant impact on the responses (disruption or depolymerization of rice straw biomass) where time had a very strong effect on the rice straw components (cellulose, lignin, and hemicellulose). The study demonstrated that the potential of the combination of Organosolv pretreatment and Bacillus sp. BMP01 hydrolysis of rice straw for enhancing sugar and ethanol yields.

The main objective of this study is to enhance the depolymerization of wheat straw biomass into its major constituents by optimizing Organosolv pretreatment conditions based on central composite design (CCD). Exposure time from 20 to 40 min, pretreatment temperature from 70 to 90 °C, and acid concentration from 60 to 80%, v/v were considered. An equal amount of formic acid and acetic acid was used in the Organosolv pretreatment to constitute the required acid concentration. In the various experiment performed, about 31.2–74.64% of cellulose were released, 62.42–71.29% of total lignin were solubilized, and 9.85–13.87% of hemicellulose were preserved in the biomass after Organosolv pretreatment. Optimum pretreatment condition was achieved at 79.5 °C, 69.5% acid concentration, and exposure time of 28.80 min. After pretreatment at this condition, the final composition of the biomass was found as follows: 74.13% cellulose, 13.54% hemicellulose (67.26% of initial hemicellulose was preserved), and 5.55 lignin (69.42% of total lignin removed). Analysis of variance (ANOVA) method was used to test the significance of the model as well as the adequacy and fitness of the experimental data into the models. It was noticeable that the exposure time, pretreatment temperature, and acid concentration influenced the pretreatment process. About 70.22% of conversion efficiency (684 mg/g) was achieved after the 10th day hydrolysis of optimally pretreated wheat straw biomass by Bacillus sp. BMP01. Ethanol yield of 40.85% was obtained by fermentation of the hydrolyzed straw. The pretreatment process significantly reduced hemicellulose solubilization that enhanced the yield of reducing sugars. The study demonstrated the possible combination of optimal Organosolv pretreatment conditions along with the microbial hydrolysis for bioethanol production from wheat straw and with possible extension to other agricultural residues.

In this study, microwave assisted NaOH pretreatment of wheat straw was thoroughly investigated using central composite design (CCD) under varying operating variables. i.e. pretreatment time, temperature and NaOH concentration. The crystallinity, crystalline length, surface microstructural change, functional group change and compositional analysis of both optimally pretreated and untreated wheat straw samples were studied. Microbial hydrolysis by Bacillus sp. BMP01 and bioethanol production was also tested for the optimally pretreated wheat straw sample. The pretreatment condition at 160 °C, 1.5% NaOH concentration and 15 min preserved high cellulose and removed high amount of lignin. At this point 38.34% of hemicellulose and 74.15% of cellulose were preserved in the solid residue and 69.49% of lignin was solubilized. An overall increase in crystallinity (from 0.3780 to 0.5610) and crystalline length (from 2.51 to 4.83 nm) were observed after the pretreatment process. Mathematical models were developed to predict the lignin removal, cellulose preserved and hemicellulose solubilization during microwave assisted NaOH pretreatment process. 718 mg/g of reducing sugar was released after hydrolysis pretreated wheat straw by Bacillus sp. BMP01. Ethanol yield of 68.2% was obtained after 96 h of fermentation. It was found that the combination of microwave assisted NaOH pretreatment at optimal condition coupled with microbial hydrolysis and C5 and C6 fermenting microbes enhanced reducing sugar and ethanol yields.

Food waste biorefineries for the production of biofuels, platform chemicals and other bio-based materials can significantly reduce a huge environmental burden and provide sustainable resources for the production of chemicals and materials. This will significantly contribute to the transition of the linear based economy to a more circular economy. A variety of chemicals, biofuels and materials can be produced from food waste by the integrated biorefinery approach. This enhances the bioeconomy and helps toward the design of more green, ecofriendly, and sustainable methods of material productions that contribute to sustainable development goals. The waste biorefinery is a tool to achieve a value-added product that can provide a better utilization of materials and resources while minimizing and/or eliminating environmental impacts. Recently, food waste biorefineries have gained momentum for the production of biofuels, chemicals, and bio-based materials due to the shifting of regulations and policies towards sustainable development. This review attempts to explore the state of the art of food waste biorefinery and the products associated with it.

Pretreatment is a vital step to enhance the yield of total reducing sugars and biofuel production from lignocellulose biomass. An effective new lignin-degrading and polysaccharide-hydrolyzing bacteria, Ochrobactrum oryzae BMP03 and Bacillus sp. BMP01 strains, were isolated and identified from wood-feeding termite's guts. Wheat straw was biodelignified by Ochrobactrum oryzae BMP03 bacteria strains to degrade lignin and to release the trapped cellulose and hemicellulose. The biodelignified wheat straw was hydrolyzed by Bacillus sp. BMP01 strains. Ochrobactrum oryzae BMP03-Bacillus sp. BMP01 consortia were also performed to analyze the effect of the simultaneous system. It was shown that the production of total reducing sugars in a separate hydrolysis system by Bacillus sp. BMP01 strain achieved 439 mg/g at 16 days of hydrolysis time, which is 9.45% higher than the simultaneous system. About 44.47% lignin was degraded by the Ochrobactrum oryzae BMP03 strain after 16 days of biotreatment. This also contributed for increment in cellulose content by 22.38% and hemicellulose content by 18.64%. The simultaneous system converted 368 mg of reducing sugars/g of wheat straw. Separate biodelignification and hydrolysis have an advantage over the simultaneous system in terms of hydrolysis efficiency and vice versa in terms of biotreatment time. Scanning electron microscope, mid-infrared analysis by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction analysis confirmed the change in composition due to biotreatment. The biotreatment improved hydrolysis efficiency, which reduces the cost of biofuel production and increases the yield of biofuel. These results indicate the possibilities of biofuel production from wheat straw by employing Ochrobactrum oryzae BMP03 and Bacillus sp. BMP01 bacteria strains.

The combination of NaOH pretreatment and microorganisms isolated from termite was used for releasing wrapped polysaccharides from wheat straw biomass matrix. Different concentrations of NaOH (1%, 3%, 5%, 7% and 10%) were considered to remove lignin and to release polysaccharides as a pretreatment method at 80°C for 4 h before subjecting it to microbial hydrolysis. Data obtained from compositional analysis of pretreated wheat straws show that a significant amount of cellulose and lignin were released after NaOH pretreatments. The amount of cellulose and lignin released was increased with increasing concentration of NaOH in the pretreatment solution. Further analysis of X-Ray diffraction, field emission scanning electron microscope and Fourier transform infrared spectroscopy confirms the removal of lignin and release of cellulose. About 69.5% of lignin was solubilized and 72.67% of cellulose was released after 10% NaOH pretreatment which was the maximum. Data from spectrophotometric analysis of reducing sugar by the 3,5-dinitrosalycilic acid method show that 83.68% (0.706 g/100 ml) of polysaccharides were converted to glucose and xylose by isolated bacteria after the 15th day of hydrolysis.

In this study, two bacterial strains capable of degrading lignin, cellulose, and hemicellulose were isolated from wood feeding termite. The isolates were identified by 16S rRNA gene sequencing. A bacterium Ochrobactrum oryzae BMP03 capable of degrading lignin was isolated on alkali lignin medium and Bacillus sp. BMP01 strain capable of degrading cellulose and hemicellulose were isolated on carboxymethyl cellulose and xylan media. The efficiency of bacterial degradation was studied by evaluating the composition of rice straw both before and after degradation. The appearance of new cellulose bands at 1382, 1276, 1200, and 871 cm(−1), and the absence of former lignin bands at 1726, 1307, and 1246 cm(−1) was observed after biodelignification. This was further confirmed by the formation of channeling and layering of the microstructure of biodelignified rice straw observed under electron microscope. Maximum lignin removal was achieved in separate biodelignification and hydrolysis process after the 14th day of treatment by Ochrobactrum oryzae BMP03 (53.74% lignin removal). Hydrolysis of the biodelignified rice straw released 69.96% of total reducing sugars after the 14th day hydrolysis by Bacillus sp. BMP01. In simultaneous delignification and hydrolysis process, about 58.67% of total reducing sugars were obtained after the 13th day of biotreatment. Separate delignification and hydrolysis process were found to be effective in lignin removal and sugar released than the simultaneous process. The bacteria, Bacillus sp. BMP01, has the ability to degrade hemicellulose and cellulose simultaneously. Overall, these results demonstrate that the possibility of rice straw bioconversion into reducing sugars by bacteria from termite gut.

In a natural ecosystem, various organisms digest and hydrolyze lignocellulose biomass efficiently. Termites are one of them. They digest lignocellulose biomass with the help of symbiotic microorganisms in their gut. Therefore, termites gut may harbor potential sources of microorganisms capable to degrade lignocellulose biomass. In this study, termite gut microbiomes of Cryptotermes brevis species were isolated and identified for their capability to degrade lignin and polysaccharides. Alkali lignin, carboxymethylcellulose, and xylan were used as the only carbon sources in the medium to isolate lignin-, cellulose-, and hemicellulose-degrading bacteria. By this method, two bacteria strains, Bacillus sp. BMP01 and Ochrobactrum oryzae BMP03 strain were isolated and identified. Bacillus sp. BMP01 strain has capabilities to hydrolyze carboxymethylcellulose and xylan to glucose and xylose, respectively. This strain showed high xylanase activity (about 0.21 U/ml) and carboxymethyl cellulase activity (about 0.25 U/ml). The ability to hydrolyze both carboxymethylcellulose and xylan makes it superior to other known cellulolytic bacteria. Ochrobactrum oryzae BMP03 strain showed laccase activity, which indicates its ability to depolymerize lignin. Lignocellulose-degrading bacteria play a vital role in the biological conversion of lignocellulose biomass to biofuel. Overall, this study shows that termite’s gut microbiomes are potential sources of lignocellulose-degrading bacteria that can be cultured and used in the biological conversion of lignocellulose biomass to biofuel.