OWIN Startup configuration for JSON serialization

Startup.cs

using System.Collections.Generic;
using System.Web.Http;
using Newtonsoft.Json;
using Newtonsoft.Json.Converters;
using Newtonsoft.Json.Serialization;
using Owin;
using Swashbuckle.Application;

namespace Project
{
    public class Startup
    {
        public void Configuration( IAppBuilder app )
        {
            var config = new HttpConfiguration();

            var defaultSettings = new JsonSerializerSettings
                {
                    Formatting = Formatting.Indented,
                    ContractResolver = new CamelCasePropertyNamesContractResolver(),
                    Converters = new List<JsonConverter>
                        {
                            new StringEnumConverter{ CamelCaseText = true },
                        }
                };

            JsonConvert.DefaultSettings = () => { return defaultSettings; };

            config.Formatters.Clear();
            config.Formatters.Add( new JsonMediaTypeFormatter() );
            config.Formatters.JsonFormatter.SerializerSettings = defaultSettings;

            config.Routes.MapHttpRoute( "api", "{controller}/{id}", defaults: new { controller = "Root", id = RouteParameter.Optional } );
            config.MapHttpAttributeRoutes();

            config.EnableSwagger( c =>
            {
                c.IncludeXmlComments( "docs.xml" );
                c.SingleApiVersion( "1.0", "Http Request Debugger" );
            } ).EnableSwaggerUi();

            app.UseWebApi( config );
        }
    }
}

This does not seem to work for middleware though.