Microbial Production of 4,4′-Dihydroxybiphenyl: Biphenyl Hydroxylation by Fungi

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Abstract
Of 15 spp. of fungi examined for their ability to hydroxylaste biphenyl, 10 produced 4-hydroxybiphenyl. Of the 10, 7 also produced 4,4''-dihydroxybiphenyl [a monomer used in the synthesis of the sulfonebiphenyl engineering polymer Radel]. The most efficient strains, Absidia pseudocylindrospora NRRL 2770 and Absidia sp. NRRL 1341, were more closely examined to determine their growth characteristics and the kinetics of biphenyl hydroxylation in batch fermentation. In the absence of biphenyl, A. pseudocylindrospora 2770 and Absidia sp. 1341 grew about as rapidly and efficiently in a defined glucose minimal medium as in a complex medium. Substrate yield coefficients for glucose in both media were 0.4-0.5 g of biomass/g of glucose; the specific growth rate was about 0.17/h (doubling time, about 4 h). In this unoptimized system, 10-15 g of biomass/l (dry wt) could be produced using a defined salt solution and glucose as sole C and energy source. In the presence of biphenyl, growth was inhibited, more for strain 1341 than for strain 2770. The specific activity for biphenyl hydroxylation (mg biphenol/g biomass) was about 3.5 times greater for strain 1341. Biphenyl hydroxylation appeared to require the presence of an oxidizable C and energy source (and perhaps growth) to proceed and, at least for strain 1341, hydroxylation seemed to be more efficient in the complex medium.