Effect of acid hydrolysis and fungal biotreatment on agro-industrial wastes for obtainment of free sugars for bioethanol production

This study was designed to evaluate selected chemical and microbiological treatments for the conversion of certain local agro-industrial wastes (rice straw, corn stalks, sawdust, sugar beet waste and sugarcane bagasse) to ethanol. The chemical composition of these feedstocks was determined. Conversion of wastes to free sugars by acid hydrolysis varied from one treatment to another. In single-stage dilute acid hydrolysis, increasing acid concentration from 1 % (v/v) to 5 % (v/v) decreased the conversion percentage of almost all treated agro-industrial wastes. Lower conversion percentages for some treatments were obtained when increasing the residence time from 90 to 120min. The two-stage dilute acid hydrolysis by phosphoric acid (1.0 % v/v) followed by sulphuric acid (1.0 % v/v) resulted in the highest conversion percentage (41.3 % w/w) on treated sugar beet waste. This treatment when neutralized, amended with some nutrients and inoculated with baker's yeast, achieved the highest ethanol concentration (1.0 % v/v). Formation of furfural and hydroxymethylfurfural (HMF) were functions of type of acid hydrolysis, acid concentration, residence time and feedstock type. The highest bioconversion of 5 % wastes (37.8 % w/w) was recorded on sugar beet waste by Trichoderma viride EMCC 107. This treatment when followed by baker's yeast fermentation, 0.41 % (v/v) ethanol and 8.2 % (v/w) conversion coefficient were obtained.

The nematicidal effect of some bacterial biofertilizers on Meloidogyne incognita in sandy soil

In a greenhouse experiment, the nematicidal effect of some bacterial biofertilizers including the nitrogen fixing bacteria (NFB) Paenibacillus polymyxa (four strains), the phosphate solubilizing bacteria (PSB) Bacillus megaterium (three strains) and the potassium solubilizing bacteria (KSB) B. circulans (three strains) were evaluated individually on tomato plants infested with the root-knot nematode Meloidogyne incognita in potted sandy soil. Comparing with the uninoculated nematode-infested control, the inoculation with P. polymyxa NFB7, B. megaterium PSB2 and B. circulans KSB2, increased the counts of total bacteria and total bacterial spores in plants potted soil from 1.2 to 2.6 folds estimated 60 days post-inoculation. Consequently, the inoculation with P. polymyxa NFB7 increased significantly the shoot length (cm), number of leaves / plant, shoot dry weight (g) / plant and root dry weight (g) / plant by 32.6 percent, 30.8 percent, 70.3 percent and 14.2 percent, respectively. Generally, the majority treatments significantly reduced the nematode multiplication which was more obvious after 60 days of inoculation. Among the applied strains, P. polymyxa NFB7, B. megaterium PSB2 and B. circulans KSB2 inoculations resulted in the highest reduction in nematode population comparing with the uninoculated nematode-infested control. They recorded the highest reduction in numbers of hatched juveniles/root by 95.8 percent, females/root by 63.75 percent and juveniles/1kg soil by 57.8 percent. These results indicated that these bacterial biofertilizers are promising double purpose microorganisms for mobilizing of soil nutrients (nitrogen, phosphate and potassium) and for the biological control of M. incognita.