Food Waste Biorefinery: Pathway towards Circular Bioeconomy.

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.

Isolation and Characterization of Novel Lignolytic, Cellulolytic, and Hemicellulolytic Bacteria from Wood-Feeding Termite Cryptotermes brevis

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

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Isolation and Characterization of Novel Lignolytic, Cellulolytic, and Hemicellulolytic Bacteria from Wood-Feeding Termite Cryptotermes brevis.

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.

Alkali pretreatment of wheat straw followed by microbial hydrolysis for bioethanol production.

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.

Biodelignification and hydrolysis of rice straw by novel bacteria isolated from wood feeding termite.

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.

Biodegradation of wheat straw by Ochrobactrum oryzae BMP03 and Bacillus sp. BMP01 bacteria to enhance biofuel production by increasing total reducing sugars yield.

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.