Acetic acid is the primary by-product generated from ethanol production by Fusarium oxysporum using glucose or xylose as a substrate. Aldehyde dehydrogenase (ALDH) is the critical enzyme in acetic acid metabolism. To decrease acetic acid yield in ethanol production, the 1509 bp DNA of aldh, encoding a 502 amino acid protein with a calculated molecular mass of 54.33 kDa and an isoelectric point of 6.21, was cloned from F. oxysporum. Sequence analysis confirmed that the screened proteins belonged to the ALDH family. A knockout vector, ∆aldh, containing positive (hygromycin resistance gene) and negative (thymidine kinase gene from the herpes simplex virus) selectable markers, was constructed. Ethanol production by the mutant (cs28pCAM-Pstal-∆aldh) in glucose- and xylose-containing media was 0.46 and 0.39 g/g, respectively, and these yields were 16.93% and 34.63% higher than those by the wild-type strain (0.393 and 0.289 g/g). Furthermore, the acetic acid yield of the mutant was 3.50 and 3.01 g/L, respectively, showing a 23.10% and 39.55% decrease compared with the wild-type strain (4.308 and 4.196 g/L). The biomass of the mutant (4.05 and 4.52 g/L) was lower than that of the wild-type strain (4.71 and 5.97 g/L). These results demonstrated the potential use of the genetically stable mutant for industrial bioethanol production.

Reintroducing crop straw into soil boosts organic matter, but natural crop straw usually shows low nutrient content. To enhance the water absorption rate of a certain thin sheet-shaped iron-containing material, a technical approach combining ball milling, the Mannich reaction, Schiff’s base cross-linking, emulsion separation, and solid–liquid adsorption was attempted to prepare iron-containing microspheres using sodium alginate and rice straw as raw materials. This approach increased the content of the trace nutrient iron and improved the water absorption rate. The results indicated that the iron-containing microspheres exhibit a diameter ranging from approximately 15 μm, an iron content of 10.44%, and a water absorption rate of 501.76%. The release rates of iron and nitrogen in soil and water within the first day were all below 15%, while the release rates after 30 days in soil were 61.8% for iron and 44.32% for nitrogen, and the corresponding rates in water were 73.1% for iron and 63.88% for nitrogen. The water absorption capacity of the iron-containing microspheres showed a trend associated with particle size and pore structure parameters. The development of iron-containing microspheres has expanded the preparation technology for semi-interpenetrating structure type sustained-release materials, and holds the potential for further development into slow-release fertilizers.