The genus Geobacillus comprises a group of Gram-positive thermophilic bacteria, including obligate aerobes, denitrifiers, and facultative anaerobes that can grow over a range of 45-75°C. Originally classified as group five Bacillus spp., strains of Bacillus stearothermophilus came to prominence as contaminants of canned food and soon became the organism of choice for comparative studies of metabolism and enzymology between mesophiles and thermophiles. More recently, their catabolic versatility, particularly in the degradation of hemicellulose and starch, and rapid growth rates have raised their profile as organisms with potential for second-generation (lignocellulosic) biorefineries for biofuel or chemical production. The continued development of genetic tools to facilitate both fundamental investigation and metabolic engineering is now helping to realize this potential, for both metabolite production and optimized catabolism. In addition, this catabolic versatility provides a range of useful thermostable enzymes for industrial application. A number of genome-sequencing projects have been completed or are underway allowing comparative studies. These reveal a significant amount of genome rearrangement within the genus, the presence of large genomic islands encompassing all the hemicellulose utilization genes and a genomic island incorporating a set of long chain alkane monooxygenase genes. With G+C contents of 45-55%, thermostability appears to derive in part from the ability to synthesize protamine and spermine, which can condense DNA and raise its Tm.

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Resilience to restricted availability of drinking water was evaluated with 44 Dorper (DOR; initial age = 3.7 ± 0.34 yr), 42 Katahdin (KAT; 3.9 ± 0.36 yr), and 42 St. Croix (STC; 2.7 ± 0.29 yr) sheep from 46 farms in 4 regions of the USA (Midwest, MW; Northwest, NW; Southeast, SE; central Texas, TX). Ad libitum water intake was determined during 2 wk of period 1, with 75% of this amount offered in 2 wk of period 2 and 50% in 5 wk (i.e., 5 to 9) of period 3. Body weight and DMI in week 2 of period 1 and week 9 of period 3 were analyzed with a mixed effects model. There was a breed × period interaction (P = 0.023) in water intake relative to BW (6.17, 6.69, and 7.19 in period 1 and 3.04%, 3.26%, and 3.36% BW in period 3 for DOR, KAT, and STC, respectively; SEM = 0.219). There were 3-way interactions of breed, region, and period in BW and DMI in g/d (P < 0.010). For STC, BW was greater (P < 0.05) in period 3 vs. 1 for all regions (50.1, 47.6, 42.4, and 45.8 kg in period 1 and 51.9, 49.3, 44.5, and 47.7 kg in period 3), whereas there was only a period difference for DOR from the MW and SE (61.4, 66.0, 64.6, and 59.6 kg in period 1 and 60.6, 66.5, 65.7, and 62.4 kg) and for KAT from TX (50.1, 47.6, 42.4, and 45.8 kg in period 1 and 51.9, 49.3, 44.5, and 47.7 kg in period 3 for MW, NW, SE, and TX, respectively; SEM = 2.57). In accordance, DMI by STC was similar (P > 0.05) between periods for all regions (1.25, 1.17, 1.06, and 1.16 kg/d in period 1 and 1.12, 1.08, 1.02, and 1.02 kg/d in period 3), as was also the case for DOR from MW and SE but not from NW or TX (1.54, 1.50, 1.30, and 1.41 kg/d in period 1 and 1.41, 1.13, 1.25, and 1.18 kg/d in period 3) and KAT from TX though not from the other 3 regions (1.47, 1.52, 1.48, and 1.40 kg/d in period 1 and 1.06, 1.15, 1.30, and 1.33 kg/d in period 3 for MW, NW, SE, and TX, respectively; SEM = 0.061). In conclusion, based on BW and DMI with water intake restricted at 50% of ad libitum consumption by individual animals, STC appeared more consistent in display of high resilience to restricted water availability, although DOR from 2 regions and KAT from 1 also were relatively resilient. The results suggest benefit to breed comparisons of inclusion of animals from multiple areas and that environmental conditions of regions may have disparate effects with different breeds of hair sheep.

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The oleaginous yeast Rhodotorula minuta has been used previously as a biocide agent and for the production of β‐carotene. In addition, R. minuta has been shown to produce up to 40% lipids, while demonstrating a faster growth rate than the similar oleaginous yeasts; Lipomyces starkeyii and R. glutinis. In this study, this promising yeast was evaluated for its potential to produce glyceride lipids under the harsh conditions and complex sugar mixtures produced from depolymerised lignocellulose. The fatty acid profile of R. minuta was not found to change significantly irrespective of the environmental conditions and contained approximately 20% palmitic acid, 5% stearic acid, 60% oleic acid and 15% linolenic acid. R. minuta was found to grow on a range of sugars, and could consume xylose and glucose when both sugars were present; however, R. minuta was found to be highly sensitive to inhibitors, such as furfurals and organic acids, formed under the harsh lignocellulose depolymerisation conditions. Accordingly R. minuta did not grow well on biomass depolymerised with an acid pre‐treatment stage. However, R. minuta was cultured successfully on food waste depolymerised with no additional acids, producing up to 19 g/l cell mass with a lipid content of up to 25% of the dry cell weight. Practical applications: While high oil productivity, fast growth rates and a suitable fatty acid composition are key traits for the economic viability of SCO production, it is essential that the organism can be cultured and produce lipids from low‐cost substrates. This requires the ability to assimilate the nutrients present in the desired hydrolysate, as well as maintain high‐growth rates in the presence of inhibitory compounds produced during the hydrolysis process. In this paper, we demonstrate that the yeast R. minuta has industrial applicability in being able to convert depolymerised waste food to lipids with a profile akin to rapeseed oil. Rhodotorula minuta lipid cultured on depolymerised food waste.

Highlights Ruminant livestock are frequently exposed to stress factors impacted by climate. A 50% water restriction increased digestibility in mature St. Croix sheep. But, ME intake did not differ because of numerical differences in feed intake. There is a variable relationship between BW and water restriction. An effect of water restriction on digestibility may influence BW.

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