Part:BBa_K2260000

Overview

The naturally occuring phaCAB operon in R. eutropha H16 is involved in biosynthesis of poly[(R)-3-hydroxybutyrate] (PHB) ___!!source!!____. It utilizes acetyl-coA, which is a product of the glycolysis pathway ___!!source!!____. Transcription of the phaCAB operon leads to expression of the following enzymes in the order: pha synthase, acetoacetyl-CoA reductase, and 3-ketothiolase. The expression of phaA leads to expression of 3-ketothiolase that converts acetyl-coA to acetoacetyl-CoA. The acetoacetyl-CoA reductase enzyme resulting from the expression of phaB leads to conversion of acetoacetyl-CoA to (R)-3-hydroxybutyryl-CoA. Finally, pha synthase leads to synthesis of PHB from (R)-3-hydroxybutyryl-CoA ___!!source!!____.

In order to utilize acetic acid present in fermented human feces ___!!source!!____, we decided to incorporate the phaCAB operon. However, literature has shown that the rearrangement of operon to phaCBA leads to higher amount of production of PHB ___!!source!!____. Thus, we obtained the operon from BBa_K1149051 and rearranged the construct from phaCAB to phaCBA and added histidine tags. The iGEM suffix is at the end of the gene construct.

PHB Weights from fermented "syn poo" supernatant

Our part was tested for production of PHB using PHB synthesis using VFAs as feedstock protocol. There were 9 replicates for our part in the "syn poo" supernatant and 3 replicates of the negative control. The OD₆₀₀ of overnights (O/Ns) was measures before inoculating the media containing VFAs. PHB was extracted using sodium hypochlorite extraction method. After resuspension of cells in 1x PBS for extraction the OD₆₀₀ was recorded to estimate the number of cells. The following table summarizes the data:

HPLC of PHB

It is known from literature that digestion of PHB in sulphuric acid leads to production of crotonic acid. We analyzed PHB obtained by digesting PHB using the PHB digestion in sulphuric acid protocol. About 0.581 g of PHB was obtained and digested for 20 mins (Low) and 30 mins (High). Lastly, an arbitrary amount was digested for 30 mins. The following figures shows the HPLC results obtained from the Low, High, and Arbitrary samples:

Low

Figure 1. HPLC results from digestion of PHB in sulphuric acid for 20 mins.

High

Figure 2. HPLC results from digestion of PHB in sulphuric acid for 30 mins.

Arbitrary

Figure 3. HPLC results from digestion of arbitrary amount of PHB in sulphuric acid for 30 mins.

The HPLC results showed that a peak for crotonic acid was seen. This confirmed the white powder obtained was PHB. However, the area of crotonic acid was low due to a number of limitations.

Nile red suspension for confirmation of PHB

Sequence and Features

Assembly Compatibility:

10
COMPATIBLE WITH RFC[10]
12
COMPATIBLE WITH RFC[12]
21
COMPATIBLE WITH RFC[21]
23
COMPATIBLE WITH RFC[23]
25
COMPATIBLE WITH RFC[25]
1000
COMPATIBLE WITH RFC[1000]

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