Effect of nonionic surfactant Brij 35 on morphology, cloud point, and pigment stability in Monascus extractive fermentation.

ABSTRACT

BACKGROUND: Nonionic surfactant Brij 35 in submerged fermentation of Monascus can significantly increase Monascus pigment yield. Here, the effects of nonionic surfactant Brij 35 on Monascus pigment secretion in extractive fermentation are discussed in terms of cell morphology, cloud point change, and pigment stability. RESULTS: At Brij 35 concentrations up to 32 g L-1 , the higher concentrations led to the loosening of the network structure on the surface of the fungal wall, enhanced cell wall permeability, and increased abundance of lipid droplets. Alternatively, when the concentration of Brij 35 exceeded 32 g L-1 , a large amount of substances accumulated on the surface of the fungal wall, permeability reduced, and the degree of oil droplet dispersion in cells decreased. Further, during extractive fermentation, Brij 35 induced formation of a grid structure on the fungal wall surface beginning on day 2, increased the number of intracellular lipid droplets, and promoted intracellular pigment secretion into the extracellular environment. When the cloud point temperature in the fermentation system approached that of fermentation, the nonionic surfactant exhibited stronger Monascus pigment extraction capacity, thereby enhancing pigment yield. Hence, Brij 35 can improve pigment stability and effectively reduce damage caused by natural factors, such as light and temperature. CONCLUSION: Brij 35 promotes the secretion of pigment by changing the fungal wall structure and cloud point, as well as by improving pigment stability. © 2020 Society of Chemical Industry.