Dataset describing the amino acid catabolism of Thermoanaerobacter strain AK85: The influence of culture conditions on end product formation

The dataset describes the catabolism of the 20 proteogenics amino acids and their end products by Thermoanaerobacter strain AK85 under different electron scavenging conditions with an emphasis on the branched-chain amino acids as reported in Scully and Orlygsson, 2019.


Data
Thermoanaerobacter strain AK85 ferments serine to a predominantly to acetate (but also minor amounts of ethanol) with and without an added electron scavenging system [1]. The branched-chain amino acids (BCAAs) valine, leucine, and isoleucine, are catabolized to their corresponding branchedchain fatty acids (BCFAs) when co-cultured with a hydrogenotrophic methanogen and to a mixture of their BCFA and branched-chain alcohols (BCOH) in the presence of 40 mM of thiosulfate [1]. Additionally, threonine is degraded mainly to acetate but also some ethanol was produced under thiosulfate and methanogenic conditions. Other amino acid were not degraded.
The influence of various culture parameters were investigated in batch culture using isoleucine as a model compound for BCAA catabolism. Table 1 details the influence of initial pH on end product formation for isoleucine while Table 2 displays end product formation as a function of cultivation temperature between 50 and 85 C. The influence of liquid-gas (L-G) phase ratio on end product formation is presented in Table 3 and the effect of initial thiosulfate concentrations between 0 and 60 mM are shown in Table 4. To investigate the effect of both L-G and initial thiosulfate concentration, a two variable experiment was conducted using isoleucine as a substrate (Table 5). Detailed kinetic experiments were performed over a period of 7 days using the valine, isoleucine, and leucine (individually) as shown in Tables 6e8, respectively.

General methods
Yeast extract was obtained from Difco while all other reagents were acquired from Sigma-Aldrich. Nitrogen gas was acquired from AGA and contained less than 5 ppm O 2 .

Microorganism and cultivation
Thermoanaerobacter strain AK85 (KR007650) (previously referred to as strain J1) was from our culture collection and 16S rRNA analysis of the strain was performed previously as described by [2] and references therein.

Value of the data
The data presents end products from the fermentation of 20 proteogenic amino acids with and without the use of a thiosulfate as an electron scavenging system by Thermoanaerobacter strain AK85, a thermophilic anaerobe isolated a hot spring in Iceland The data set shows the influence of culture parameters on the fermentation of a branched-chain amino acid, L-isoleucine, in batch culture, as well as a kinetic experiment showing the formation of branched-chain fatty acids and alcohols from branched-chain amino acids Could be a useful for comparing the amino acid catabolism of other mesophilic and thermophilic anaerobes producing higher-value C4 and C5 alcohols.
Specifications        Filled to a V f of 1 L; 1 mL aliquots were frozen at À40 C prior to use. The vitamin solution was prepared according to DSM 141 and consisted of (on a per L basis): biotin (2.0 mg), folic acid (2.0 mg), pyridoxine-HCl (10.0 mg), thiamine-HCl$2H 2 O (5.0 mg), nicotinic acid (5.0 mg), D-Ca-pantothenate (5.0 mg), cobalamin (0.1 mg), p-aminobenzoic acid (5.0 mg), and lipoic acid (5.0 mg); the vitamin solution was stored at À20 C prior to use. The medium was assembled by adding the 1 M phosphate buffer (pH 7.0) and yeast extract to distilled water containing resarzurin and boiled for 10e15 min until pink; the solution was cooled to ambient temperature under a stream of nitrogen (<5 ppm O 2 ). The mixture was then transferred to serum bottles and autoclaved (121 C) for 60 min. All other components of the medium were added separately through filter (0.45 mm) sterilized solutions. Substrates were provided at a concentration 20 mM unless specifically stated otherwise stated. All fermentations were done at 65 C and at pH of 7.0 with a liquid-gas (L-G) ratio of 1:1 without agitation except when stated otherwise. All inoculations were performed using cultures taken from the exponential growth phase using an inoculation volume of 2% (v/v). Overnight stocks cultures of strain AK85 were cultivated on glucose (20 mM). All cultivations were performed as triplicates.

Amino acid substrate utilization with and without electron scavenging systems
The 20 proteogenic amino acids were cultivated as single substrates (20 mM) with or without the addition of thiosulfate (40 mM).

Effect of initial pH on isoleucine fermentation
To investigate the effect of pH on the end product profile from isoleucine, strain AK85 was cultivated in Hungate tubes (15 Â 150 mm) in BM containing 20 mM of isoleucine and 20 mM of thiosulfate at pH ranging from pH 4.0 to 9.0 with 0.5 pH unit intervals. End products were determined after 14 days of incubation.

Effect of temperature on isoleucine fermentation
To investigate the effect of temperature on growth, strain AK85 was cultivated at 50 Ce85 C in 5 C intervals in Hungate tubes (15 Â 150 mm) as otherwise described in section 2.4. End products were determined after 14 days of incubation.

Effect of liquid-gas phase ratio
Strain AK85 was cultivated in serum bottles (57 mL nominal volume) which were filled with either 4.5, 13.4, 26.5, 36.0, or 45.0 mL of BM medium containing isoleucine (20 mM) and thiosulfate (20 mM) to give L-G values of 0.09, 0.34, 0.98, 2.12, and 5.62, respectively. End products were quantified after 14 days of cultivation.

Effect of initial thiosulfate concentration
The effect of initial thiosulfate concentration on isoleucine (20 mM) degradation pattern was investigated with initial thiosulfate concentrations between 0 and 60 mM. The experiments were performed Hungate tubes (15 Â 150 mm) as otherwise described in section 2.4. End products were determined after 14 days of incubation.