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Document Type

Thesis - University Access Only

Award Date

2014

Degree Name

Master of Science (MS)

Department

Dairy Science

First Advisor

Sanjeev Anand

Abstract

Membrane separation techniques have grown to be a part of the main unit operations for dairy process model and product development. However, in the processing of dairy fluids, the physico-chemical attributes of the feed stream have a great influence on membrane biofouling. Study 1 investigated the influence of different dairy feed substrates on reverse osmosis (RO) membrane biofilm formations and also the differences in their cleanability to a six-step CIP. Resistant Bacillus sp., 48h old static biofilms were formed to evaluate for viable counts and morphology. Study 2 was aimed to remove different kinds of membrane biofilms by developing improved cleaning strategies, especially at the enzyme and sanitizer cleaning steps. Cleaning efficacy was determined by comparison of decline in culturable cells from biofilms before and after cleaning modifications. The results of study 1 showed that UF permeate fouled membrane biofilm pretreatment counts were the highest compared to whey+ UF and whey biofilms. It was also left with highest number of Bacillus survivors after the six step cleaning cycle. Even the microscopy images revealed the difference in the microstructures of various biofilms,with UF permeate biofilms showing more soiling and the nano-structures showed higher surface roughness indicating intensified bacterial colonization among all others. The results from this study indicate that one type of CIP protocol may not be applicable in the same way on different kinds of biofilms formed by different RO feed substrates. The results of study 2 showed that the enzymes such as alkaline phosphatase, β- galactosidase, and Everlase (a protease) when used along with surfactant combinations at pH 11.0 were found to be the most effective enzymes in the CIP application, both individually and in combination with the existing protease enzyme on whey+ UF permeate biofilms. A formulated sanitizer based on chlorine dioxide was also found to be better than the control CIP treatment when compared to the other kinds of sanitizers. The results from this study indicate that if a dairy processor were to apply a standard CIP on high pressure membranes, then a further addition with a formulated alkaline phosphates enzyme at the enzyme step with the existing Savinase (protease) enzyme along with a replacement at the sanitizer step with a formulated chlorine dioxide sanitizer would reduce residual biofouling further. Further pilot scale studies are required to determine the industrial applicability of these modifications to ensure the best match between the outcomes of these developmental trails and the requirements of industrial applications.

Library of Congress Subject Headings

Dairy processing
Biofilms
Membrane separation
Membranes (Technology)
Reverse osmosis

Description

Includes bibliographical references (pages 100-110)

Format

application/pdf

Number of Pages

140

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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