Reflections on the journey: six short stories.

One of the goals of the 2011 International Year of Chemistry is to celebrate the contributions of women to science. A question that has been frequently asked in this regard is... Why is it necessary to highlight women in the "age of equality"? The reasons are varied but the facts are that many women scientists worked in obscurity throughout the 19th and even well into the 20th century, sometimes publishing anonymously to be heard. This celebration of Women in Science is one way to recognize both the resiliency and passion of these women. As part of this celebration, Chemistry Central Journal's Thematic Series of "Women in Chemistry" includes this article describing the path several women took as they pursued chemistry careers spanning the latter part of the 20th century and into the early 21st century. Sharon Haynie, Nancy Jones, Cheryl Martin, Paula Olsiewski, Mary Roberts and Amber Hinkle each have unique story of their personal journey from childhood to adulthood. As you read these stories, listen generously, and feel free to share your own stories, comments and thoughts.

Functional expression of prokaryotic and eukaryotic genes in Escherichia coli for conversion of glucose to p-hydroxystyrene.

The chemical monomer p-hydroxystyrene (pHS) is used for producing a number of important industrial polymers from petroleum-based feedstocks. In an alternative approach, the microbial production of pHS can be envisioned by linking together a number of different metabolic pathways, of which those based on using glucose for carbon and energy are currently the most economical. The biological process conserves petroleum when glucose is converted to the aromatic amino acid L-tyrosine, which is deaminated by a tyrosine/phenylalanine ammonia-lyase (PAL/TAL) enzyme to yield p-hydroxycinnamic acid (pHCA). Subsequent decarboxylation of pHCA gives rise to pHS. Bacteria able to efficiently decarboxylate pHCA to pHS using a pHCA decarboxylase (PDC) include Bacillus subtilis, Pseudomonas fluorescens and Lactobacillus plantarum. Both B. subtilis and L. plantarum possess high levels of pHCA-inducible decarboxylase activity and were chosen for further studies. The genes encoding PDC in these organisms were cloned and the pHCA decarboxylase expressed in Escherichia coli strains co-transformed with a plasmid encoding a bifunctional PAL/TAL enzyme from the yeast Rhodotorula glutinis. Production of pHS from glucose was ten-fold greater for the expressed L. plantarum pdc gene (0.11mM), compared to that obtained when the B. subtilis PDC gene (padC) was used. An E. coli strain (WWQ51.1) expressing both tyrosine ammonia-lyase(PAL) and pHCA decarboxylase (pdc), when grown in a 14L fermentor and under phosphate limited conditions, produced 0.4g/L of pHS from glucose. We, therefore, demonstrate pHS production from an inexpensive carbohydrate feedstock by fermentation using a novel metabolic pathway comprising genes from E. coli, L. plantarum and R. glutinis.

Calcium alginate bead immobilization of cells containing tyrosine ammonia lyase activity for use in the production of p-hydroxycinnamic acid.

An Escherichia coli catalyst with tyrosine ammonia lyase activity (TAL) has been stabilized for repeated use in batch conversions of high tyrosine solids to p-hydroxycinnamic acid (pHCA). The TAL biocatalyst was stabilized by controlling the reaction pH to 9.8 +/- 0.1 and immobilizing the cells within a calcium alginate matrix that was cross-linked with glutaraldehyde and polyethyleneimine (GA/PEI). We found a GA range where the bead-encapsulated TAL was not inactivated, and the resulting cross-linking provided the beads with the mechanical stability necessary for repeated use in consecutive batch reactions with catalyst recycle. The GA/PEI calcium alginate TAL catalyst was used in 41 1-L batch reactions where 50 g L(-1) tyrosine was converted to 39 +/- 4 g L(-1) pHCA in each batch. The practical usefulness and ease of this process was demonstrated by scaling up the TAL bead immobilization and using the immobilized TAL catalyst in four 125-L bioconversion reactions to produce over 12 kg of purified pHCA.