Overproduction of palmitoleic acid from corn stover hydrolysate by engineered Saccharomyces cerevisiae.

Palmitoleic acid (POA) has been widely applied to nutrition and pharmaceutical industry. However, high cost of scale-up fermentation restricts the extensive application of POA. Hence, we investigated the availability of corn stover hydrolysate (CSH) as carbon source in POA production by engineered S. cerevisiae. Although the yeast growth was inhibited to some extent by CSH, the POA production with CSH was slightly higher than that with pure glucose. The C/N ratio of 120 and addition of 1 g/L lysine raised the POA titer up to 2.19 g/L and 2.05 g/L, respectively. Two-stage cultivation could increase the POA titer by upregulating the gene expression of key enzymes in fatty acid synthesis pathway. A high POA content of 57.5% (v/v) and a highest POA titer of 6.56 g/L were achieved under the optimized conditions. These findings provide a feasible approach for sustainable production of POA or its derivatives from CSH.

Environmental factors shape sediment anammox bacterial communities in hypernutrified Jiaozhou Bay, China.

Bacterial anaerobic ammonium oxidation (anammox) is an important process in the marine nitrogen cycle. Because ongoing eutrophication of coastal bays contributes significantly to the formation of low-oxygen zones, monitoring of the anammox bacterial community offers a unique opportunity for assessment of anthropogenic perturbations in these environments. The current study used targeting of 16S rRNA and hzo genes to characterize the composition and structure of the anammox bacterial community in the sediments of the eutrophic Jiaozhou Bay, thereby unraveling their diversity, abundance, and distribution. Abundance and distribution of hzo genes revealed a greater taxonomic diversity in Jiaozhou Bay, including several novel clades of anammox bacteria. In contrast, the targeting of 16S rRNA genes verified the presence of only "Candidatus Scalindua," albeit with a high microdiversity. The genus "Ca. Scalindua" comprised the apparent majority of active sediment anammox bacteria. Multivariate statistical analyses indicated a heterogeneous distribution of the anammox bacterial assemblages in Jiaozhou Bay. Of all environmental parameters investigated, sediment organic C/organic N (OrgC/OrgN), nitrite concentration, and sediment median grain size were found to impact the composition, structure, and distribution of the sediment anammox bacterial community. Analysis of Pearson correlations between environmental factors and abundance of 16S rRNA and hzo genes as determined by fluorescent real-time PCR suggests that the local nitrite concentration is the key regulator of the abundance of anammox bacteria in Jiaozhou Bay sediments.