Monascus pigments (MPs) have been used as food colorants for several centuries in Asian countries and nowadays in the whole world via Asian catering. The MPs biosynthetic pathway has been well-illustrated, however, the functions of a few genes including mrpigH in the MPs gene cluster of M. ruber M7 are still unclear. In current study, mrpigH was disrupted in Δmrlig4ΔmrpyrG, a highly efficient gene modification system, using mrpyrG as a selection marker, and ΔmrpigHΔmrlig4ΔmrpyrG::mrpyrG and ΔmrpigHΔmrlig4ΔmrpyrG have been obtained. Subsequently, their morphologies, biomasses, MPs and citrinin (CIT) production were analyzed, respectively. These results have revealed that the deletion of mrpigH has significant effects on the morphology and growth of M. ruber M7. Moreover, compared with M. ruber M7, the yields of MPs and CIT were drastically increased and decreased in mrpigH mutants, respectively.

Aqueous enzymatic method is a green oil extraction technology with limited industrial application owing to the need for demulsification of the oil body intermediate product. Existing demulsification methods have problems including low demulsification rates and high costs, such that new methods are needed. Free fatty acids produced by lipid hydrolysis can affect the stability of peanut oil body (POB) at a certain concentration. After screening even-carbon fatty acids with carbon chain lengths below ten, caproic acid was selected for demulsification of POB using response surface methodology and a Box–Behnken design. Under the optimal conditions (caproic acid concentration, 0.22%; material-to-liquid ratio, 1:4.7 (w/v); time, 61 min; and temperature, 79 C), a demulsification rate of 97.87% was achieved. Caproic acid not only adjusted the reaction system pH to cause aggregation of the POB interfacial proteins, but also decreased the interfacial tension and viscoelasticity of the interfacial film with increasing caproic acid concentration to realize POB demulsification. Compared with pressed oil and soxhlet-extracted oil, the acid value and peroxide value of caproic acid demulsified oil were increased, while the unsaturated fatty acid content and oxidation induction time were decreased. However, the tocopherol and tocotrienol contents were higher than those of the soxhlet-extracted oil. This study provides a new method for the demulsification of POB.

Plants do need a fixed proportion of carbon (C), nitrogen (N) and phosphorus (P) elements to maintain normal metabolic activities. The P fertilizers are widely used to supplement nutrients in subtropical plantations. Stoichiometric homeostasis reflects the strategy of plants to cope with various environments (including P fertilizer supply rate). It is thus of great significance to understand C:N:P stoichiometry in the plant-litter-soil system under P addition and stoichiometric homeostasis of plant tissues for fertilization management of slash pine (Pinus elliottii Engelm) plantations. We measured the C, N and P contents in root, branch, needle, litter and soil in slash pine plantations fertilized with four treatments - P1 (25 kg P ha−1 yr−1), P2 (50 kg P ha−1 yr−1), P3 (100 kg P ha−1 yr−1), and a control (CK) in subtropical China and calculated stoichiometric homeostasis of plant tissues. Results showed that P addition increased the capacity of needle to obtain C, N and P elements and altered the C:N:P stoichiometry of plant tissues, as well promoted the accumulation of C and P elements in soil, but had no significant effect on soil stoichiometry. The nutrient contents of needle and branch were higher than those of root and litter, indicating that slash pine was more inclined to allocate nutrient to the aboveground tissues. The stoichiometric homeostasis of C, N and P among plant tissues was ranked as follows: root > branch > needle, and homeostasis of nutrient elements in the needle was C > N > P. This indicated that the C, N and P stoichiometric homeostasis was various among plant tissues and elements types under P addition. These findings suggest P addition would alleviate the P limitation of slash pine growth in subtropical regions. In the future, long-term observation experiments should be conducted and the trade-off between P addition rates and economic and ecological benefits should be considered.