The metabolic function of 2,3-butanediol is not known, although some have speculated that it was an evolutionary advantage for these microorganisms to produce a neutral product that's less inhibitory than other partial oxidation products and doesn't reduce the pH as much as mixed acids.
ðə mˌɛɾəbˈɑːlɪk fˈʌŋkʃən ʌv tˈuː,θɹˈiːbjˈuːteɪndɪˌɑːl ɪz nˌɑːt nˈoʊn, ɔːlðˈoʊ sˌʌm hæv spˈɛkjʊlˌeɪɾᵻd ðˌɐɾɪt wʌz ɐn ˌɛvəlˈuːʃənˌɛɹi ɐdvˈæntɪdʒ fɔːɹ ðiːz mˌaɪkɹoʊˈɔːɹɡənˌɪzəmz tə pɹədˈuːs ɐ nˈuːtɹəl pɹˈɑːdʌkt ðæts lˈɛs ɪnhˈɪbɪtˌoːɹi ðɐn ˈʌðɚ pˈɑːɹʃəl ˌɑːksɪdˈeɪʃən pɹˈɑːdʌkts ænd dˈʌzənt ɹᵻdˈuːs ðə pˈiː ˈeɪtʃ æz mˈʌtʃ æz mˈɪkst ˈæsɪdz.