الفهرس 
Literature reviewOnly 14 pages are availabe for public view
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Abstract
Climatic problems caused by burning fossil fuels and the depletion of these energy resources are one of the most important factors that urge human to search for clean and renewable energy resources. Conversion of the renewable Biomass for biofuel production have been introduced to solve such problems. Bioethanol beside hydrogen gas and biodiesel are forms of clean biofuel energy resources that can be produced from conversion of the renewable biomass.
Chitin the main constituent of insect exoskeleton, is the second most abundant biopolymer in nature after cellulose, the renewal of the chitin biomass is estimated in the order of 1010 to 1011 tons on earth annually. The present study suggested tapping the chitin of insects’ biomass represented by the American cockroach to be a new, renewable, and promising alternative source for bioethanol production.
1. Cockroach chitin extraction and characterization
Chitin from P. americana was extracted using new simple technique, a 1 M NaOH was used for integumental proteins removal and chitin purification. The physicochemical properties of the extracted chitin and two standard chitin commercial samples were characterized using FTIR, XRD, SEM and EA techniques. The data of the extracted chitin was compared to the data of the commercial samples (chitin of crab and chitin of shrimp). characteristics of the extracted chitin was to a great extent similar to the standard samples and chitin sample extracted in the literature studies. The degree of acetylation and the crystallinity index are factors that may indicate the purity of the extracted chitin. The degree of acetylation was calculated using FTIR data and EA data, while XRD data was used for calculating the CrI.
Fourier Transform Infra-Red Spectral analysis for chitin samples
The FTIR data revealed that the extracted chitin exhibited an α-form the same result was conducted for crab and shrimp chitin since splitting at the amide I spectral peak was observed at ≈ 1655 and 1625 cm-1 for the three samples. The DA was calculated to be 108.7% for the extracted chitin, 106.9% for crab chitin and 107.2 % for shrimp chitin. Rapprochement of DA values between the three samples indicates the high purity of the extracted chitin considering the two standards are already commercial products with high purity.
X-Ray Diffraction patterns analysis for chitin samples
The XRD patterns for the three sample also revealed a great similarity in their crystallinity. The crystallinity index CrI was calculated to be 85.7 % for the extracted chitin, 82.5 % for crab and 83.72% for shrimp chitin. Rapprochement of CrI value between the three samples indicates the high purity of the extracted chitin considering the two standards are already a commercial product with high purity.
Scanning electron microscopy (SEM) for the chitin samples
Scanning the surface morphology of the three samples with SEM revealed that all of them exhibited general common characteristics, all were mainly composed of thick rough chitin crystals (flakes), nanofibers and microfibers. The extracted chitin from P. americana was observed to have large numbers of isolated nanofibers at different magnification power, while crab chitin was observed to have a sieve-like structure with nanopores and tubular structure with nanopores was observed during scanning of shrimp chitin.
Elemental analysis and chitin content
The C, H, N content for the three samples was determined by elemental analysis and the degree of acetylation was calculated. The DA dropped from 306.3% for the dried exoskeleton of P. americana to 103% for the extracted chitin that means an efficient removal of proteins and inorganic materials were conducted since the DA of the extracted chitin reproached the DA of completely acetylated chitin (100 %) also it was quite differed from crab 107% and shrimp chitin 94%. Rapprochement of DA values between the three samples indicates the high purity of the extracted chitin considering the two standards are already commercial products with high purity. The chitin content in the dried exoskeleton was calculated to be ≈20%.
The results revealed that the simple extraction technique was to a great extent sufficient for extraction of high quality and pure α-chitin from the American cockroach P. americana. Such results highlight the American Cockroach to be a promising alternative source for easily extracted chitin.
2. Cockroach Chitin biotransformation
The extracted chitin was then used as carbon source in submerged fermentation for production of bioethanol. Five fungal strains, T. harzianum Rifai AUMC5408, M. anisopliae AUMC2837, B. bassiana AUMC 3067, Mucor circinelloides van Tieghem AUMC 6017 and Mucor circinelloides AUMC 6027 were screened for their chitinolytic activity on the extracted chitin at different pH values (2-8), pH 4 was the most optimum value for degradation of the extracted chitin and production of NAG for almost all the strain used.
Cockroach chitin biotransformation to N-acetylglucosamine (NAG)
Among the five fungal strains used T. harzianum Rifai AUMC5408 achieved the highest chitinolytic activity on the extracted chitin at pH 2-8. It could produce 6.338±0.86 g/l from 15 g/l colloidal chitin, followed by M. anisopliae AUMC 2837 (5.878±0.168 g/l), followed by B. bassiana AUMC 3067 (3.178±0.235 g/l), followed by Mucor circinelloides AUMC 6017(0.183±0.016 g/l), and the minimum chitinolytic activity was observed for Mucor circinelloides AUMC6027 (0.117±0.011 g/l).
Cockroach chitin biotransformation to ethanol
T. harzianum AUMC 5408 was screened for its ability to enhance the production of ethanol by Mucor circinelloides AUMC 6017 and Mucor circinelloides AUMC 6027. Degradation of chitin using 5408 was conducted for 96 hours. The obtained chitin derivatives (including NAG) was then subjected to fermentation process with Mucor circinelloides AUMC 6017 and Mucor circinelloides AUMC 6027 at pH 4 for 48 hours. Mucor circinelloides AUMC 6017 produced 11.92 ±0.068 g/l ethanol from15 g/l colloidal chitin (79.5 % of colloidal chitin biotransformed to ethanol), while Mucor circinelloides AUMC 6027 produced 2.68±0.035 g/l ethanol from 15 g/l colloidal chitin (17.9 % of colloidal chitin biotransformed to ethanol).
Finally, Mucor circinelloides AUMC 6017 and Mucor circinelloides AUMC 6027 were screened for direct ethanol production from chitin Mucor circinelloides AUMC 6017 showed a great potentiality in ethanol production directly from chitin, it could to produce 11.22 ±0.312 g/l ethanol from 15 g/l colloidal chitin (74% of colloidal chitin biotransformed to ethanol) after 6 days of incubation at 28 oC and pH 4, while Mucor circinelloides AUMC 6027 produced 1.94±0.05 g/l from 15 g/l colloidal chitin (13% of chitin biotransformed to ethanol) after 6 days of incubation at 28oC pH 4.
The obtained results are very promising in highlighting the insect biomass represented by P. americana as a renewable alternative feed-stock of bioethanol production