Question: What is the use of emulsion PCR in Next Generation Sequencing?

Context:
Emulsion PCR-coupled target enrichment: an effective fishing method for high-throughput sequencing of poorly preserved ancient DNA
We present a unified strategy in which emulsion PCR is coupled with target enrichment followed by next-generation sequencing. The method made it possible to obtain efficiently non-duplicated reads mapped to target sequences of interest, and this can achieve deep and reliable sequencing of ancient DNA from typical materials, even though poorly preserved.
Three multiplex PCR reactions were carried out to amplify the coding exons of 328 genes including FBN1, TGFBR1 and TGFBR2. DNA fragments from different samples were ligated with barcoded sequencing adaptors. Template preparation and emulsion PCR, and Ion Sphere Particles enrichment were carried out using an Ion One Touch system. The ion sphere particles were sequenced on a 318 chip using the PGM platform.
In our NGS approach, the 16,569-bp mtDNA is enriched by long-range PCR and the 108 nuclear genes (which represent 1301 amplicons and 680 kb) are enriched by RainDance emulsion PCR. Sequencing is performed on Illumina HiSeq 2000 or MiSeq platforms, and bioinformatics analysis is performed using commercial and in-house developed bioinformatics pipelines.
However, pyrosequencing of emulsion PCR reactions, amplifying from only one molecule at a time, can generate megabases of clonally amplified loci at high coverage, thereby greatly simplifying allelic sequence determination.
During genomic PCR, in this 4-primer system, the outer set of primers containing the MID and the 454 adaptor sequences are incorporated into an amplicon generated by the inner HLA target-specific primers each containing a common sequence tag at the 5' end of the forward and reverse primers. Pools of the resulting amplicons are used for emulsion PCR and clonal sequencing on the 454 Life Sciences GS FLX System, followed by genotyping with Conexio software.
The purpose of our study was to compare NGS enrichment methods for a clinical assay targeting the nine genes known to be associated with aortopathy. RainDance emulsion PCR and SureSelect RNA-bait hybridization capture enrichment methods were directly compared by enriching DNA from eight samples.
We show the efficacy by comparing the method to a commercial kit and further demonstrate that emulsion PCR can be used for bias free amplification and virtual immortalization of DNA template libraries.
Here, we describe a novel approach for normalization of multiplex next generation sequencing libraries after emulsion PCR.
Briefly, amplified libraries carrying unique barcodes are prepared by fluorescent tagging of complementary sequences and then resolved by high-speed flow cytometric sorting of labeled emulsion PCR beads.
The protocol is simple and provides an even sequence distribution of multiplex libraries when sequencing the flow-sorted beads. Moreover, since many empty and mixed emulsion PCR beads are removed, the approach gives rise to a substantial increase in sequence quality and mean read length, as compared to that obtained by standard enrichment protocols.
Based on the mechanism of emulsion PCR, a unique DNA template would only generate a unique sequence read after being amplified and sequenced on GS FLX.
Prior to SOLiD sequencing reaction, the libraries were amplified with emulsion PCR and enriched with the P2 enrichment beads. The library samples were loaded to sequencing Chip for Work Flow Analysis (WFA) or sequencing running with default parameters.

Answer: Prior to Next Generation Sequencing reactions, DNA libraries are constructed, amplified with emulsion PCR, and enriched with the use of enrichment beads. The library samples are then loaded to a sequencing chip and analyzed on an NGS platform.