Development and application of efficient pathway enumeration algorithms for metabolic engineering applications.

Metabolic Engineering (ME) aims to design microbial cell factories towards the production of valuable compounds. In this endeavor, one important task relates to the search for the most suitable heterologous pathway(s) to add to the selected host. Different algorithms have been developed in the past towards this goal, following distinct approaches spanning constraint-based modeling, graph-based methods and knowledge-based systems based on chemical rules. While some of these methods search for pathways optimizing specific objective functions, here the focus will be on methods that address the enumeration of pathways that are able to convert a set of source compounds into desired targets and their posterior evaluation according to different criteria. Two pathway enumeration algorithms based on (hyper)graph-based representations are selected as the most promising ones and are analyzed in more detail: the Solution Structure Generation and the Find Path algorithms. Their capabilities and limitations are evaluated when designing novel heterologous pathways, by applying these methods on three case studies of synthetic ME related to the production of non-native compounds in E. coli and S. cerevisiae: 1-butanol, curcumin and vanillin. Some targeted improvements are implemented, extending both methods to address limitations identified that impair their scalability, improving their ability to extract potential pathways over large-scale databases. In all case-studies, the algorithms were able to find already described pathways for the production of the target compounds, but also alternative pathways that can represent novel ME solutions after further evaluation.

Centering osteotomy for treatment of posterior shoulder dislocation in obstetrical palsy.

BACKGROUND: The main objective of this study is to describe a new surgical technique that, through a gleno-humeral approach, reduces the incongruent joint while a humeral head centering osteotomy achieves shoulder stabilization. A humeral medial derotational osteotomy is performed associated with the articular reduction. PATIENTS AND METHODS: Fourteen patients with obstetrical palsy presenting a posterior humeral head dislocation were submitted to a centering osteotomy procedure. Our study included patients with: (1) more than 1.5 years postoperative follow-up, (2) presence of humeral head posterior dislocation. The exclusion criteria were the following: (1) patients with total flaccid paralysis, (2) low paralysis and (3) any kind of active infection at the time of the procedure. RESULTS: Before treatment, in all patients, the shoulder joint was posteriorly dislocated and in internal rotation. All patients went on to have successful healing at the osteotomy site. In all cases, an improvement in the functional Mallet scale was observed. In all patients, except one, the posterior dislocation was corrected. In two cases, a second surgery (external derotation osteotomy) was performed to improve the upper extremity's position. CONCLUSIONS: Articular congruency, after posterior dislocations of the humeral head, is achieved by humeral head centering osteotomy in patients with obstetrical palsy late deformities and also improves function. LEVEL OF EVIDENCE: Level IV; case series.