A coherence theorem for pseudo symmetric multifunctors

Yau defines the notion of pseudo symmetric $\mathbf{Cat}$-enriched multifunctor between $\mathbf{Cat}$-enriched multicategories and proves that Mandell's inverse $K$-theory multifunctor is pseudo symmetric. We prove a coherence theorem for pseudo symmetric $\mathbf{Cat}$-enriched multifunctors. As an application, we prove that pseudo symmetric $\mathbf{Cat}$-enriched multifunctors, and in particular Mandell's inverse $K$-theory, preserve $E_n$-algebras ($n=1,2,...,\infty$), at the cost of changing the parameterizing $E_n$-operad.